SCHOLARLY REVIEWS International Journal of Sport Nutrition, 1992,2, 1 -T9
rnfluence of Diet and Exercise on Energy Expenditure-A Review R. Scott Van Zant Maintenance of a healthy body weight results from equating total enegy intake to total energy expenditure (resting metabolic rate, RMR, the thermic effect of feeding, TEF; the thermic effect of activity, TEA, and adaptive thermogenesis, AT). Dietary quantity and composition and acute and chrvnic exercise have been shown to influence all components of total energy expenditure. This paper reviews the effects of exercise and diet on energy expenditure and, ultimately, energy balance. Overnutrition increases RMR and TEF while undernutrition decreases them. Carbohydrate and protein oxidation is closely tied to intake whereas fat oxidation does not closely parallel fat intake. Thus excess fat intake is likely to lead to fat storage. Acute endurance exercise at >70%VQmax increases postexerciseRMR and TEF.Chronic exercise training may increase RMR while also increasing TEF. Review of the research indicates that energy balance may best be achieved by consuming an energy appropriate, low fat diet complemented by endurance exercise.
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Approximately 25% of the adult Anierican population may be considered obese (97). Obesity, as a contributingrisk factor in such conditions ascardiovascular disease, hypertension, and diabetes, is recognized as a prominent health concern in western society. Thus the importance of maintaining a.healthy body weight and percent body fat, thereby reducing the risk of deveroping obesity, becomes readily apparent. Weight maintenance results from achieving a state of energy balance in which total energy intake from food is matched by total energy expenditure, composed primarily of resting metabolic rate, the thermic effect of feeding, and physical activity. Many factors are associated with dietary intake, exercise, and their interaction, which may influence energy expenditure and, as a result, m l the simple equation of energy balance (energy stored = energy in - energy a bit more complex. This article reviews the effects of dietary quantity composition, and acute and chronic exercise training on overall energy e ture. Additionally, dietary and exercise considerations for maintaining en .i I balance are discussed. R. Scoa Van Zlur~is wirh t Beltsville Human Nutr. Res.
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Influence of Diet and Exercise / 3
considered (18,21), and this genetic effect eould have a significant influence on an individual's ability to maintain x?nergy,bMance throughout life (21, 82). Thermic effect of feeding is the energy expended in excess of resting metabolic rate for the digestion, absorption, transport, metabolism, and storage of food and it accounts for approximately 10% of daily energy expenditure (49). Thermic effect of feeding is composed of 'two components, termed obligatory and facultative thermogenesis. Obligatory thermogenesis is the energy required to take up and metabolically process ingested food; according to Horton (46), it accounts for 50-75% of the*total thermic effect of feeding .response. The remaining increased energy expenditure is considered facultative thermogenesis and may have its origin in increased sympathetic nervous system activity (53) and metabolic cycling (64) resulting from food ingestion. Thermic effect of feeding is influenced by a number of factors including the caloric content and composition of the meal consumed (5, 49), the nutritional state and antecedent diet of the individual (5, loo), individual genotype (76), and level of physical fitness (75). The host variable component of daily human energy expenditure is thermic effect of activity which, according to Poehlman (70), may account for as little as 15% or as much as 30% of overall daily energy expenditure. Under conditions of weight maintenance energy intake, increased energy expenditure: through purposeful physical activity provides the means of inducing short-term energy deficits that could result in weight loss. As will be,discussed later, alterations in thermic effect of activity, and the resulting physiological effects.accompanying long-term physical training, may influence resting metabolic rate and thermic effect of feeding. The final component ofdaily energy expenditure, adaptive thermogenesis, may be considered as changes in ,normal status of daily energy expenditure, primarily via alterations of resting metabolic rate and thermic effect of feeding, as a result of environmental andlor physiologiml stresses. Alterations in heat ~ ~ characteristically production with no apparent change in physical F W O may describe the effect of adaptive thermogenesis. Poehlman and Homn (71) suggest that nonshivering thermogenesis during cold exposure, increasesldecreases in metabolism with overfeedinglundernutrition, and changes in resting metabolic rate and,thermic effect of feeding as a result of chroniG exercise training may all be considered as examples of adaptive thermogenesis. Horton (46) indicates that while changes in daily can account for no m over time might have a
Dietary Effects on Ehergy .Expenditure q
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Both quantity and composition of the diet may influenee overall energyexpenditure. It is well established that severe undernutrition results in a decrease in resting metabolic rate in both animals and humans beyond that accounted for by weight loss (6,9, 1l , 3 & "45; 50,63; 90). Such a metabolic adaptation may serve as a protective mechanism to prevent excessive loss, of energy stored in vital tissues during periods of starvation (50, 7'0). Thet decrease in resting metabolic demased sympathetic rate duringsevere tmdernutitionismost likely a result of, nervous activity (53) and thyroid hormone -function f28)1~ Several Jnvestigators
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.(31,45,70) have ~uggestedthat ~tbreduced,restingMietabulk rate seen during severe caloric~restrictio1~(5800 kealaday-I [3349 kJ]) may act to inhibit successful I weight loss. Some investigators have .shown that endurane-e exercise during caloric resn-iction may prevent a decline In relative (expressed per kg fat frees mass) resting metabolic rate. (9+011, 5 1, 56: 63), while othms have reported no effect of exerciseon maintainingrelati~e~estingmetabolicrate~duringcaloric atstriction (43,45, 69)' The vari~onsseen in -theeffect .of exercise on resting metabolic rate during caloric .restriction may be a function a!€the sevetity of .caloric restriction applied. In general, w e r e calmic xestri-ction limi@the impact that exercise may exert -on, maintainzing -relative =sting metabolic m e (43,45,69). H m v e ~Mwle , et aL (63) have s h m "thatd 33% w i ~ c t i m ~~i nl a t i v eresting metabolic rate induoed by 2 weeks ~f~ttevere (580 ~kcaltday-'12093 caloric restriction could be ! r e d"bya 2-week daj1y exierci9e (60% +0max)regimen that results in an kcrease in fat free mas. During mild to moderate caloric restriction, exercise has been shown to maintain relative resting metabvlic rate.zin 'both humans (51,t;563 and animals (9, 11). It would ,thewfme appear t h a the degreeof caloric "restictiot~affects the apability of m a d s e to reverse the demase$in relative resting metabolic rate induced by defiiits in energy intake. Additionzlly,*thelength of exmcise mining may have m impact m resting metabolic "rate d d n g energy restriction. Ballor et 81. f9) mated tha in raw~theeffects of exercise in attenudeereases in "re"l?~dve resting me@xboiic mte during caloric te3triction were not statistically siflcant until the 10th 1k*oftraining. While undernutrition results in a decrease in resting metabulie rate, overnnMon a w e s an increase in 'both ratingmetabolic rate and~tkm"1c effect of feeding (6, 48, 49, 85, 99, 100).~.Aside from theA M o n s increase in energy expenditure a s ~ i a k Wlth d ,~emetabolic processing 0%overfeedig, sympathetic ner~ousraaivity(53) ;mnd thymid hm@neTfmctiorl (29) are increased during periods mf mmutri.eiori~Thesaltor8tion in. resting metabolic rate and themic ovmtftrition may be influenced by mch factors effect of Teeding as a ~emlt~rsf BS d i a r y mmpmition, carrentenergy stores the body, 8d heredity (5, 85, " 100). .' Bjrnmrop and Sj4;9.osnwni"16j indicate $hat hm'ans have ~onilja limited aM1izy to'icdnveft exc& dietary iearbohydrrzPtr: Ro fat iztia de now, fatty acid as a remit acuteiemess intake of carbohydrate is most effectively ~prhesis,~and and increasingresting giumse oxidation. handled by maximizing ,glycogen Ingestiorh, df a asingl~large (500 g) mrbohyirate imeal results -in maximizing muscle glycogen storage and increasing the resting rate of carbohydrate oxidation while decmsing *therateof fat metabolism (3)' The inorease in carbohydrate oxidation is mediated by an increase in sympathetic nervous system activity, atmmnting for as mmh as: 3040 offthe increased glmcose-indud thennogenesis
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A c et 41.~ (5) demonstrated .thdt anteoedent;&et may significantly affect .resting MiefBbrrIic yare and Rhm-ic e'ffect of .feeding f611owing a l q i;arbdhydmte ~ m z lSubjects . were fed ;either iahigh M, ;mixed, or high casbohydraediet mm1xdap j_primj to&onstmifig 2~500-gcarbohplm meal: Cmbo%@mmidMon.;md e I!poge&mere Significanflyrednced.anthe high.Ztlt diet when eotrqared mthe*mixedmd tzrbohydrate ricH Wtmmts, indicating that
tk.fateof tkmbohjrdt-at&iheaI~was largelyyfbrfitfSr~e"glyhgen syntHesis-:*The authors'additionally noted that the degree of li~oeenesisinduced bv a single large the k e c r:dent diet A
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drate and protein tend to vary with their intake fromsthe diet. Nitrugens is maintained on adequate protein intake, whether the total amount of: fat oxidation does ients (Ion]g chain or
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Influence of Diet and-Egemr'$&/ I
r&titr&*~~gen.~tonmptieii~msared~d'~lrin"g~th~i"gh ~fa&diwmd~da&gI a controhdiet fed;tmtheknbji?'ctWlNeePprkr toebeginffing$he leetogeni'c d i e They suggestithat thisirt4sulbin lig~rbf~theysignificPant reductiotliimhole-body glacose oxidationMdemonstraZes the vbody'mbility To adapt overallvtnetabolism to the I prevailingrenergy substrate conditions in order to sparercarbohydrate. , D i e t w compositiontmay aiso~influencdgenergyexpenditure t h b m h its inlpact on thermic effect of activity. Increasedienergy intake of fat atzthe~xpense :influenee dne's abilitya'to perfomr, at higher wmercise of ~c&bohydrate*;,may intirhsities~Duriflgmild'tomoderate intensity exercise (700/ V02max)~however,carbllydmtB ~ ;serves aspthe primary exercise.energy ~ s o ~ r c d r ~ :.*;+ ~dy, , r;a,'-l~z$ , * J B X &hi*$ .- 14 Undert.such exercise con"ditions2jstudiewha~kPdentdn~&e&~th~md~ced dietmy8carbohydratesconsumption ( 9 3 3 % 4totalrmergy vs'fromwrbohydrate) signifiantly decreases,,exercise time"aio faggueu(n13, 24,~80) %It%& a result of significant reductions.inmuscle glycogen stores prbr tmxercise.-Tj52+80). FuW# research &$neededtordetermine the minimum level of dietary cmbdhydrate that e )ex will adequately support high intensity endurance exercise.
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:* 3 &er0ise5~pose~~~bot!h (single ,bout$and.chromc (long-term%@&hgjjE3ffect9 on oV&dl *energyexpenditure in%humans.The :most obvims dercise effec0 oh ener=:expenditurwis-through+tRe thermic effect of activity. The greaterethe energy~outputthrough;lpurposeful physical activitypflhe greater-the overall daily energpxpendituiiejBouchard et al. (22) recently reported a significant reductiod percent body fat in~ubjectsWho were fed a constant energy !days while also exercising 6 days a week (106 min daily) at a erate (55% VOpmax)intensity. Several more clinically oriented investigations 4 1,51,101) have also shown, in both men and women, that regular endurance.
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gations studfi~guhe'effectsfe%rcised8Modywei-gh;t: induces only modest changes in total bodyeweight o s s , ~ fat ~ f mass may be greater than the loss of total body! ch cases~assessingexercise effectiveness by total body weight may mass loss. While dietary * z during weight loss. of an increased metabolic response &WatfsingletabmrC of, cently termed excess postexercise o~gen4jcunsumption,*wi: een established (30). Unfortunately, research-in this area'ffas to fully describe the phenomenon. Studies have shown that the duratior of %
EPOC may vary from W to 24 hm padtexmcker, A ~ r e w bresting g metaMfc rate arrywhm f m 1 to 25% (8,14,23~30,36:J9,5% 66: 864 100). A~rrumber of methodological variations (subjeetfimesslw??l,'type andintrnity of metxis6 measurement period, meals taken dming m & m e n t period) may asconnt, 8t feast in paafor the disparity in metabolic r e d B seen among these investigatims~ Amonthe more recent.invmtigations, it appears tEr;et the bulk of an EPOC period occurs within the first hour following exercise,.and that the EPOC tends f@ be greater with imemde4cerCise intensity (>70% V02max)andduratifm (>60 min) (23, 39-86), While the totalxenergyexpaditme #ofEPOC (0.7-71.7 kcal [T3300 W]) from a single exercise bout r n a ~ b eminor, when cms?dered Mpm of a regular exercise regimen tkiv energy odtpat 014%time: m I d help to maintain i atis energy balance* The substratesource of thiskrea~ededergyexpendinrrefo~Tdgemci3e dep&dsion exercise4atensity atK1 darat?on*Several imestigams Rave s R W a significant reduction in the respiratory q.&ent" faIlowing~.ex~~ise,~~ttre~by indicating #hcremedfat dxidation ~(8,14, 39, #58+100). Thei@edudimin the post&efcise respiratorg!q ~ i ~diltectljr ~ i related-to s the durztfon rrnd irytmslty of the exercise bout, Vigorous +J70%% q ~ r n a x exercise ) of extended'dt~ation (>60 min) depletes m~scleiglymgenand theley q a i ~ an s imreee in fat oxidation to continue suppIying exercise e n ~ ; ~ i f ? r p n * c e 8 ~ of a t fexwcise, m fatty acid levels may mairr*elevatedfor up to 2 4 W posmercise(58);ind this diminished glucose utilization postexercise allows more exbgemus glucose to be used for the repletion of muscular,glycogen (39) , ,I * The physiologic mechanisms resulting in EPOC have not kendetermined, though resynthesis of a:de"n(rsimrriphsphate, creatine p b s ~ W v j ~ p t e ! and in, glycogen in skeletal muscle is certainly a part 6T the mrly campo&nt bf EPOC, Recent -studiesby Weststrate and Wautvast (1mshow that the increasein restirrg met&bolicrate seenlfollowing~t;xhaustive trycling exercise c m be red&ed when the ,extsrcise is+pwededrby4days of pragre&ve carbohydrate overfeeding. of EPOC Ac~wdingto the anthorsr these findings indicate t M a large smpment~ may be related to energy expended to refill mnscle.glycogen stores. ,Gaesser an& Brook$(38) have gated that my -fat:torsdnflutncingmirocfmndrial axygen consumption will contribute to EPUC. Therefore Stlch FWdrs as metirbolic h m m e (catecholamines,thyroxinei glu~:rxmicoids"$ cont~r?nWaPIma calcium ion concentration, sodium pump acthity, and W y Pempmtm? will hrfluence EPOG, Newsholrne (64)has also made %*casefor-stlbstrafe cycling (interconversion of metabolic intermediates which ~ 1 1 for ~ greater s en~yhe ex&se sensitivity) 8s a possible compomt of EPOC, A~equiva~ent-Bbsolute worklottds, EPOC seems to be reduced itr tmimd swbjem (42):This wmfd s e h Iogical since trained .d: subjects have a gerrerallyt*depressed~ 3overall metabolic - responses to a given *mercise:morkloMwhen compared to mtrained' ~ub$?cts. Sem1"~investigfftor~~ employittg both lungitudinat (54,?56) end cross sectimal>(73,74?75,78, 93, 94) mthods, have shown TRat mmpzued'to the m ~ a i n e d ~ ~ ~ strretabolic ting rate issincreased as a resalt of-clwonic end@rm1 exercise training, Poehlman et aI. C75) *identifiedpr linearrelations2ff between f r ~ m a find. k relative resting metabolh rate in grrPung~males, More-;recently, Poehlman qdbcollm@esr have dmonstr*d that entiuram exercise trttinirfg (as defined.& VOzmax) am'ounts&x a small bubsignificant prticrtuof thC variatrdrr in resting rnetaibolic rate in nmobae older men (73) and rronobek you@femaIes
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Influence of Diet and Exemise / 9
C78.751The.8 ~ t h o rdo s .cautim that vhile these-" ~ m ~ ~sd-te' t i m ~a rel8tWishily between a 'high level ,of endurance training and increased resting metabolicrate, it doe$mtnecessad1ydmo~te~icause-and-~fect~relationship, since the influence sf training on both resting meta'bolic rate and V0,max may e dependent (72, 79). he level of endurance training may sign~~cantly affect the ability of endurance exercise to influence resting metabolic rate. Tremblay et ak. (93) heamred r&ng metabolic7rate in wntrained, mmlerately mained 7{;5-L48 8hrs of vigorous %&ly exercise), and highly traine"B (12-16 hrs of vigorous Weekly exercise) yaung male subjects. Theif findings showed ~-thal?*relative;7esting metabolic rate was significantly increased in the highly trained subjeetsdwhile there wasym dgnificant diffeence in relativelrestbg metabolic between the untrained and moderately trained' subjects. Other investigators have fa?led to show a difference ih restifig imetabolic rate as a result of endurance &&cise mining. Binghm~&%l.*(15) failledm find a+difference in basal mtabolie rate, overnight metabolicb-rate, or sleeping metabolic .rate in subjects follopling 7 weeks of endurance#+(.IjealWj@)~exacise trainingirVnforhmately, the study popnlation m 3 rather smMl (N=6) ,and the m a n relative-.~0~rnax posttraining (-5 1 ml.k.gihin-') might be consideredmly as rmodemtely trained. Schwlz et al. 70 x ml-kg-l.ain:') and-antmined y m g mdes in a respiratorychamber and found no differbetween the tW groups. The tests were cond1etedQdays posttraining while feeding;subjects a weight rr&ntenmee diet which, in the case of the trained subjects, was considerably less food than normally m~sumed.. ' a , ; 'r Schulz et al. noted it is possible tfMtre2ewted resting mdtablic fate ~ 4 t h exrdise training may be psent~onlytwwrhigh Iwels of ia'efi~ityittfematched withiphigh caloric in-take. The elevated%re$tingmetabolic Batemoted 4n Xghly mined individuals might therefore be a short-term adautation to thaknhanced energyturnover assoli~ted'withkhr0nic physicdl training: The mdy of Tremblay et al. (94) might tmd to &pport this hypothesis, as they showala 6.6% drop in resting imet#bolk rate of highly trained subjeets following 3adaymof dettaining! -, %.The~mechanisrn4qvwhichfrolonged endurance exercise6 training might inckase resting metabolic rate is notclear; hasrtewr~Poehlfmn&all-(75)duggest that restleg metabolic rate-may'be affected b3.adHi'gh'icaloric Imntwer (inheased energy intake and expenditure) in a state a$ energy balance. .am3 might be e~plainedin part via substratecyding,dncea high volume of enetflnx through a metabolic system would andoubtedly- require lelevated enzyme activity. An additional factor to conside%tmi~htbe afl acmm~lative~ EPOC ~ieffeet,since exercise intmsi* duration,: and ?reqbenty m e 811 increased in:l&hly ttrained mbjects, end since themic effect of meals,&iken.pmtexercise mwy be in-eased (58, 61, 87):. 8 ..a -, k R d t s from m e a l hwst+@ors ,indicatewW.a%4ll;g1e 'boat of mil$ to mckltx'ate-imtene, e ~ d s exerts e a "pt3kntiting eff%tron tWfElieieffect of feeding (58,62, 87, '88, 89, ,JfOO)k This effect seems most pronounced in lean individuiPls and,h@"%e6i te~61tof&creai3ed sefisitivitqto thennogenic hormones in these tindilriduals wb,comparedto~abese&%jects(87, 88). AdditioWlIy; icfre t h i n g of'the exerei%*relative to*thBMteal&ky influence themagnitude of the enhancement of t h i c effecb&feaing. "Segal et al. (88') showed that kclean
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10 / Van Zant
subjects the thermic effect of feeding was most pronounced when the meal was consumed prior to exercise, while in obese subjects the thermic effect of feeding was greatest when the meal was consumed after exercise. The enhanced thermic effect of feeding in the obese postexercise, when compared to the lean subjects, may be a result of both an increase in glucose uptake by skeletal muscle as a result of exercise and an increase in thermogenic hormone levels and sympathetic nervous activity (88). ' Contrary to the above findings, several investigators have found exercise to have little if any enhancing effect on thermic effect of feeding (12, 25, 26, 98). Several methodological factors could explain some of the variation seen in the results of the various studies in this area. Welle (98) noted that few studies which have fed meals of less than 900 kcal(3,767 kJ) have seen enhanced thermic effect of feeding associated with exercise. Some studies that have failed to show an enhanced thermic effect of feeding with exercise measured oxygen consumption for a short time (60 min or less) (12, 26) or had brief sampling periods (2 min) over several hours (25). Additionally, exercise duration has varied substantially in these studies. Several studies failing to show increased thermic effect of feeding with exercise have used short (15 min or less), intermittent exercise bouts (25, 98), while many studies demonstrating a potentiating effect of exercise on thermic effect of feeding have used prolonged (30-80 min), continuous exercise bouts (58,62,88,89, 100). It is also important to recall that there is a significant degree of inconsistency and conflicting results in the general area of thermic effect of feeding research. Lack of standardized protocols and incompletely described methods have resulted in a wide variety of answers to the various research questions related to thermic effect of feeding (17). While still the topic of some debate, it appears that chronic exercise training which results in a high degree of fitness tends to decrease thermic effect of feeding. In their cross-sectional study of 28 young male subjects covering wide ranges in maximal aerobic capabilities (defined both by VOzmax and level of endurance training), Poehlman et al. (75) demonstrated a curvilinear relationship between V02max and thermic effect of feeding. Thermic effect of feeding was highest in moderately trained individuals whereas it was lower in the highly trained and untrained, This curvilinear response may explain why some studies have shown a linear relationship of V02max and thermic effect of feeding (44), especially if the sample size or range of fitness levels was limited. It is possible that in the untrained a reduced sensitivity to insulin may be the cause of the decreased thermic effect of feeding;while in the highly trained a decreased sympathetic nervous activity as a result of chronic exercise training may result in a decreased thermic effect of feeding (75). It should also be recalled that highly trained individuals have an elevated resting metabolic rate, which might tend to mask a portion of the facultative component of thermic effect of feeding. Finally, a strong genetic component to thermic effect of feeding has been demonstrated that could also influence individual response in this measurement (77).
Considerations for Maintaining Energy Balance Maintaining a healthy body weight has been recognized as an imp a healthy lifestyle (92). Leanrindividuals are at lower risk for c disea~e,~diabetes, hypertension, and stroke. Compared to the obese, lean individa-
Influence of Diet and~Exercl;iee/ 111
- d si show1sgreatm~emitiYity&in b m ~ & b 6 . H ~ r W ~ n e ~ 8 eand-: s p dthtertf~re; ~ ~ e an enhane&kapacity to'prmessdsmrces &ofenergy~:in"~th@ fa~ehof~~arious metabolic demandsibsince botlndictaryq~antityand coi4ipbsit~onas .pell~%Hracuteand %hroniciiexercisetrainingaaffeat allifacetsoftdaily energy e~pendituliepitseems importabt,to consider thme dietary,andlexcrcise effectscthat might seem most appr~priate~ain attaining and/ortmaintainingr.energy balance. a ~~,k o B, , a Sin~e:~in6reased~physical dactivitya-as dq4result+ of purposeful eWoist,will Jd~rease~themicieffect of activity,d would4seem logical that+regzuI;riif&d~~$n~e eeruercise~~ollld play aneimportant~roleaiinrrnaintainingenergpbalanch Regular physical activity may also influence ca1ofic:intake. In,a study of malt Indian :Roy, and Mitras(60) - m e d thaLc8loric intakeaincrdsed in rnillwork:ers~tMayer, those@vorkrsi whose~miyityfell.bebw&8.r: :normal! Zone' ', (defined3asfmediuh to nlightmcMty work), *For ~ w o r k e r ~ ~ ~ w ~ e : : a c tdevels i v i t y were at, or: abovd the nornralaone, mlori-o intzke closelyspml.leled.rcalo~&ex~endft&6r~ This is anrrlogous*totanihalmodels, iniwhich-activity restriction.i+ithout caloriwdestris$4 i$t >%+*,, a 8 ?,id tion results in overmting,and obesity (59). -, pi"dditiohally,j intense physical .trainin@kommonlys&duves ~esptfnseiof dinfinished appetitq which may~occuwtsaresult ofithefelmatedbodptern~erarn avsociated with thisxtype of.trAning (7); Thoughfassociatedmore-&th.Goderate to high levels-of physical fitness, th&&ffectsof exercise on restinghetdbolic~rate and thermic effectsf feeding mustdalso be considered asyadditional meansby , : which regula~exercise could help maintain -energy$balance. 1nterestingly:ithe overall effeetivetiesaof .exercise in dedreahifig adiposity lmaynbe gender dependenb ~Std?Iiessinvestigaingt h e effektivenkssmf a.20-week aerobiaexerciserprogram .on body ~Tarnt3ssmd aadipade*tibu&fun&'on4ndtedtthat males~demmstrated,~~ignificant reduction incbody+w&ght+"fa-t'idass,petment:ifat, and*fatIIcellxweightswhile, fem'ales ,sh+owed,:ito significant changerbr4hese parametets ,g(29,t 92)t:r Additionallyj*,while training increased epr'rrephrinrn stimfilafed rlfpolysis~im both males and-femrrles, ,the inkrerra-ivasa-considerablP more ,pronounced in males (+66%) than in females (+46%). The results of these studiessuggest that, while both males,and,femalesmay lose fatmass withregular enduranse exercise training, males may be+moresensitive to the:effects of exercise on adiposity than females. a Pfbb ".' t t. Y hjt ,* A@the primary soume of:energy, utilized by athe eentralrfftervo%s system, * $-to f 2: nf ~BgMl u t rmal ~ & d u l l a : r a ~ d ~ ~ ~ d ~ B l o d d ~ ~ l P s , ~ ~ p ~ l i i &in pHysialagical-fudCrimi.i.Fla~,i'(33)~bijted, in light of the hum%fl'~ratw~lirnited abilitydo storeacarbokrfrdrat&* ' 'it -would s6em that$biokogical %volutimt-would have a been~colnpelled-to de~lopkmech%nismsgiving highei%priority>to the presmatibmf carbohydrate:baIante" (p. 305). The body therefore seeks to attain an appropriate carbohydrate~;balance~ throrgh dietary intake. In: Western societie~sverthapast~50 yemt thericontenbt9f fat in the typical diet has increased ap~r~~i~dtely+20%~to&level Where it constitutes 43% of total energy consumed (40)r"Undert&ese+dietarjrcond"lTion9#consumptionof f d ~ in d an' effort to&sfin:taih barbehydrate ba'lance cawlead to a wnsumption of dietary fat beyond Metabolib need, which rtltimatElyleads to an%8ccumulationof body fat and possible onset 4rr4i 4 9 :%a ~i x", , of obesity, b i j r Ix matt3m ) s A m a a~ a ~ ~ & n a . ' s o d ~ ~ ~ ~ o 9 ~ r l i ~ ~ @ e ~ @ . M 1 ~ @ emdin in & e a ~ ~ ~ t t j . ~ d u n dfile~e0iRp~sitia:fi"df ifio~~ ~W~di~cnrus~~a1l~1trthe composition a f theTue"ra~idizedJTo~11ustrate thisXpdntihe irstes that the food
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quotient (ratio of carbon dioxide formed to oxygen utilized during combustion of the diet) of the typical western diet (total energy partition: 45% carbohydrate, 40% fat, 15% protein) is 0.85, while the respiratory quotient following an overnight fast is 0.82. If energy balance is to be maintained over the course of the day, the respiratory quotient must equal the food quotient. If the daily respiratory quotient exceeds the daily food quotient, a greater proportion of carbohydrate was oxidized, resulting in an overall carbohydrate deficit. If carbohydrate balance is to be reestablished on the typical mixed diet, food will be consumed in amounts exceeding actual energy expenditure, with the excess energy derived from fat being stored. It is therefore important to maintain an equilibrium between dietary intake of fat and oxidation of fat through activity. Such a condition may be achieved by either limiting fat intake (increasing the dietary food quotient by consuming a high carbohydrate diet), increasing activity of sufficient intensity and duration (mild to moderate endurance type exercise which tends to elicit lower respiratory quotients) to increase fat oxidation, or combining both factors. In final consideration of the reviewed research, it would seem that a balanced diet sufficient in protein, low in fat (530% total energy), and rich in complex carbohydrate may be the most appropriate for apparently healthy humans (96). Such a diet should be complemented by regular endurance exercise of an intensity and duration appropriate for the physical capabilities of the individual. If weight loss is desired, dietary restriction should come mostly from fat sources and should not be severe, thereby reducing the risk of decreasing resting metabolic rate through severe undemutrition. Prolonged exercise of mild to moderate intensity would also be a logical component of any weight loss regimen, as it would add to the overall energy deficit while serving to maintain resting metabolic rate in a state of undernutrition (37, 51, 63). The increased energy expenditure through exercise would also decrease the magnitude of the energy deficit required from caloric restriction in an attempt to achieve a healthy body weight.
The flux of energy through the metabolic systems of the human is a dynamic, multifaceted process. Variations in energy intake, physical activity, environmental factors, and genetic background make the study of human energy expenditure a most complex task. In considering the effects of diet and exercise on energy expenditure, one must understand how they influence each of the component parts of total energy expenditure. Total dietary content influences resting metabolic rate, resulting in a decreased resting metabolic rate during undernutrition and an increased resting metabolic rate with overfeeding. These dietary-induced changes in resting metabolic rate result from alterations in sympathetic nervous system activity and metabolic hormone function. Dietary composition may affect energy expenditure. The body maintains precise metabolic control of carbohydrate and protein by altering oxidation rates of these nutrients, since their storage capacity in the body is limited. Less stringent control is required of fat, since excess dietary fat is readily stored at minimal metabolic expense. Excess intake of fat not only leads
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10. Ballor, D.L., and R.E. Keesey. A meta-analysis of the factors affecting exerciseinduced changes in body mass, fat mass, and fat-free mass in males and females. Int. J. Obes. (in press). 11. Ballor, D.L., L.J. Tommerup, D.P. Thomas, D.B. Smith, and R.E. Keesey. Exercise training attenuates diet-induced reduction in metabolic rate. J. Appl. Physiol. 68:2612-2617, 1990. 12. Belko, A.Z., T.F. Barbieri, and E.C. Wong. Effect of energy and protein intake and exercise intensity on the thermic effect of food. Am. J. Clin. Nutr. 43:863-869, 1986. 13. Bergstrom, J., L. Hermansen, E. Hultman, and B. Saltin. Diet, muscle glycogen, and physical performance. Acta Physiol. Scand. 7 1:140-150, 1967. 14. Bielinski, R., Y. Schutz, and E. Jequier. Energy metabolism during postexercise recovery in man. Am. J. Clin. Nutr. 42:69-82, 1985. 15. Bingham, S.A., G.R. Goldberg, W.A. Coward, A.M. Prentice, and J.H. Cummings. The effect of exercise and improved physical fitness on basal metabolic rate. Br. J. Nutr. 61:155-173, 1989. 16. Bjomtrop, P., and L. Sjostrom. Carbohydrate storage in man: Speculations and some quantitative considerations. Metabolism 27(Suppl. 2): 1853-1865, 1978. 17. Blondheim, S.H., B. Mendelson, P. Hashkes, and R. Aranne. Dietary thermogenesis: Why the conflicting results? In Recent Advances in Obesity Research: V , E.M. Berry, S.H. Blondheim, H.E. Eliahou, and E. Shafrir (Eds.), London: John Libbey & Co., Ltd., 1987, pp. 151-154. 18. Bogardus, C., S. Lillioja, E. Ravussin, W. Abbott, J.K. Zawadzki, A. Young, W.C. Knowler, R. Jacobowitz, and P.P. Moll. Familial dependence of the resting metabolic rate. N. Engl. J. Med. 315:96-100, 1986. 19. Bouchard, C. Heredity and the path to overweight and obesity. Med. Sci. Sports Exerc. 23:285-291, 1991. 20. Bouchard, C., A. Tremblay, J-P. Despres, A. Nadeau, P.J. Lupien, G. Theriault, J. Dussault, S. Moorjani, S. Pinault, and G. Fournier. The response to long-term overfeeding in identical twins. N. Engl. J , Med. 322:1477-1482, 1990. 21. Bouchard, C., A. Tremblay, A. Nadeau, J-P. Despres, G. Theriault, M.R. Boulay, G. Lortie, C. Leblanc, and G. Foumier. Genetic effect in resting and exercise metabolic rates. Metabolism 38:364-370, 1989. 22. Bouchard, C., A. Tremblay, A. Nadeau, J. Dussault, J-P. Despres, G. Theriault, P. Lupien, 0. Serresse, M. Boulay, and G. Foumier. Long term exercise training with constant energy intake. 1. Effect on body composition and selected metabolic variables. Int. J. Obes. 1457-73, 1990. 23. Brehm, B.A., and B. Gutin. Recovery energy expenditure for steady state exercise in runners and nonexercisers. Med. Sci. Sports Exerc. 18:205-210, 1986. 24. Christensen, E.H., and 0. Hansen. Zur methodik der respiratorischen quotientbestimmung in Ruhe und bei Arbeit 111 [Nourishment and the capability to work]. Arbeits Faehigheit Emaehmng. Scand. Arch. 81:160-171, 1939. 25. Dagenais, G.R., A. Oriol, and M. McGregor. Hemodynamic effects of carbohydrate and protein meals in man: Rest and exercise. J. Appl. Physiol. 21: 1157-1162, 1966. 26. DaIIosso, H.M., and W.P.T. James. Whole-body calorimetry in adult men: 2. The interaction of exercise and over-feeding on the thermic effect of a meal. Br. J. Nutr. 52:65-72, 1984. 27. Danforth, Jr., E. Diet and obesity. Am. J. Clin. Nutr. 41:1132-1145, 1985. 28. Danforth, Jr., E. The role of thyroid hormones and insulin in the regulation of energy metabolism. Am. J. Clin. Nutr. 38:1006-1017, 1983.
!35-239, 1' energy reql 1935. ~d W.M. B weight los
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48. Jequier, E. Carbohydrates: Energetics and performance. Nutr. Reviews 44:55-59, 1986. 49. Jequier, E., and Y. Schutz. Long-term measurements of energy expenditure in humans using a respiration chamber. Am. J. Clin. Nutr. 38:989-998, 1983. 50. Keys, A,, J. Brozek, A. Henshel, 0. Mickelson, and H.L. Taylor. The Biology of Human Starvation, Vol 1. Minneapolis: University of Minnesota Press, 1950. 51. Kiem, N.L., T.F. Barbieri, M.D. Van Loan, and B.L. Anderson. Energy expenditure and physical performance in overweight women: Response to training with and without caloric restriction. Metabolism 39:651-656, 1990. 52. Kirwan, J.P., D.L. Costill, J.B. Mitchell, J.A. Hournard, M.G. Flynn, W.J. Fink, and J.D. Beltz. Carbohydrate balance in competitive runners during successive days of intense training. J. Appl. Physiol. 65:2601-2606, 1988. 53. Landsberg, L., and J.B. Young. The role of the sympathetic nervous system and catecholamines in the regulation of energy expenditure. Am. J. Clin. Nutr. 38:10181024, 1983. 54. Lawson, S., J.D. Webster, P.J. Pacy, and J.S. Garrow. Effect of a 10 week aerobic programme on metabolic rate, body composition and fitness in lean sedentary females. Br. J. Clin. Pract. 41684-688, 1987. 55. Lean, M.E.J., and W.P.T. James. Metabolic effects of isoenergetic nutrient exchange over 24 hours in reIation to obesity in women. Int. J . Ohes. 12: 15-27, 1988. 56. Lennon, D., F. Nagle, F. Stratman, E. Shrago, and S. Dennis. Diet and exercise training effects in resting metabolic rate. Int. .I. Obes. 9:39-47, 1985. 57. Lissner, L., D.A. Levitsky, B.J. Strupp, H.J. Kalkwarf, and D.A. Roe. Dietary fat Clin. . Nutr. 46386and the regulation of energy intake in human subjects. Am. .I 892, 1987. 58. Maehlum, S., M. Grandmontagne, E.A. Newsholme, and O.M. Sejersted. Magnitude and duration of excess postexercise oxygen consumption in healthy young adults. Metabolism 3.5425-429, 1986. 59. Mayer, J., and D.W. Thomas. Regulation of food intake and obesity. Science 156:328337, 1967. 60. Mayer, J., P. Roy, and K.P. Mitra. Relation between calorie intake, body weight, and physical work: Studies in an industrial male population in West Bengal. Am. J. Clin. Nutr. 4:169-175, 1956. 61. McNeill, G., A.C. Bruce, A. Ralph, and W.P.T. James. Inter-individual differences in fasting nutrient oxidation and the influence of diet composition. Int. .I. Ohes. 12:455-463, 1988. 62. Miller, D.S., P. Mumford, and M.J. Stock. Gluttony 2: Thermogenesis in overeating man. Am. J. Clin. Nutr. 20: 1223-1229, 1967. 63. Mole, P.A., J.S. Stem, C.L. Schultz, E.M. Bemauer, and B.J. Holcomb. Exercise reverses depressed metabolic rate produced by severe caloric restriction. Med. Sci. Sports Exerc. 21:29-33, 1989. 64. Newsholme, E.A. The interrelationship between metabolic regulation, weight control, and obesity. Proc. Nutr. Soc. 41: 183-191, 1982. 65. Otton, M.H., G. Hennemann, R. Docter, and T.J. Visser. The role of dietary fat in peripheral thyroid hormone metabolism. Mefaholism 29:930-935, 1980. 66. Passmore, R., and R.E. Johnson. Some metabolic changes following prolonged moderate exercise. Metabolism 9:452-456, 1960.
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rnfluence of Diet and Exercise on Energy Expenditure-A Review R. Scott Van Zant Maintenance of a healthy body weight results from equating total enegy intake to total energy expenditure (resting metabolic rate, RMR, the thermic effect of feeding, TEF; the thermic effect of activity, TEA, and adaptive thermogenesis, AT). Dietary quantity and composition and acute and chrvnic exercise have been shown to influence all components of total energy expenditure. This paper reviews the effects of exercise and diet on energy expenditure and, ultimately, energy balance. Overnutrition increases RMR and TEF while undernutrition decreases them. Carbohydrate and protein oxidation is closely tied to intake whereas fat oxidation does not closely parallel fat intake. Thus excess fat intake is likely to lead to fat storage. Acute endurance exercise at >70%VQmax increases postexerciseRMR and TEF.Chronic exercise training may increase RMR while also increasing TEF. Review of the research indicates that energy balance may best be achieved by consuming an energy appropriate, low fat diet complemented by endurance exercise.
.
Approximately 25% of the adult Anierican population may be considered obese (97). Obesity, as a contributingrisk factor in such conditions ascardiovascular disease, hypertension, and diabetes, is recognized as a prominent health concern in western society. Thus the importance of maintaining a.healthy body weight and percent body fat, thereby reducing the risk of deveroping obesity, becomes readily apparent. Weight maintenance results from achieving a state of energy balance in which total energy intake from food is matched by total energy expenditure, composed primarily of resting metabolic rate, the thermic effect of feeding, and physical activity. Many factors are associated with dietary intake, exercise, and their interaction, which may influence energy expenditure and, as a result, m l the simple equation of energy balance (energy stored = energy in - energy a bit more complex. This article reviews the effects of dietary quantity composition, and acute and chronic exercise training on overall energy e ture. Additionally, dietary and exercise considerations for maintaining en .i I balance are discussed. R. Scoa Van Zlur~is wirh t Beltsville Human Nutr. Res.
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Influence of Diet and Exercise / 3
considered (18,21), and this genetic effect eould have a significant influence on an individual's ability to maintain x?nergy,bMance throughout life (21, 82). Thermic effect of feeding is the energy expended in excess of resting metabolic rate for the digestion, absorption, transport, metabolism, and storage of food and it accounts for approximately 10% of daily energy expenditure (49). Thermic effect of feeding is composed of 'two components, termed obligatory and facultative thermogenesis. Obligatory thermogenesis is the energy required to take up and metabolically process ingested food; according to Horton (46), it accounts for 50-75% of the*total thermic effect of feeding .response. The remaining increased energy expenditure is considered facultative thermogenesis and may have its origin in increased sympathetic nervous system activity (53) and metabolic cycling (64) resulting from food ingestion. Thermic effect of feeding is influenced by a number of factors including the caloric content and composition of the meal consumed (5, 49), the nutritional state and antecedent diet of the individual (5, loo), individual genotype (76), and level of physical fitness (75). The host variable component of daily human energy expenditure is thermic effect of activity which, according to Poehlman (70), may account for as little as 15% or as much as 30% of overall daily energy expenditure. Under conditions of weight maintenance energy intake, increased energy expenditure: through purposeful physical activity provides the means of inducing short-term energy deficits that could result in weight loss. As will be,discussed later, alterations in thermic effect of activity, and the resulting physiological effects.accompanying long-term physical training, may influence resting metabolic rate and thermic effect of feeding. The final component ofdaily energy expenditure, adaptive thermogenesis, may be considered as changes in ,normal status of daily energy expenditure, primarily via alterations of resting metabolic rate and thermic effect of feeding, as a result of environmental andlor physiologiml stresses. Alterations in heat ~ ~ characteristically production with no apparent change in physical F W O may describe the effect of adaptive thermogenesis. Poehlman and Homn (71) suggest that nonshivering thermogenesis during cold exposure, increasesldecreases in metabolism with overfeedinglundernutrition, and changes in resting metabolic rate and,thermic effect of feeding as a result of chroniG exercise training may all be considered as examples of adaptive thermogenesis. Horton (46) indicates that while changes in daily can account for no m over time might have a
Dietary Effects on Ehergy .Expenditure q
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Both quantity and composition of the diet may influenee overall energyexpenditure. It is well established that severe undernutrition results in a decrease in resting metabolic rate in both animals and humans beyond that accounted for by weight loss (6,9, 1l , 3 & "45; 50,63; 90). Such a metabolic adaptation may serve as a protective mechanism to prevent excessive loss, of energy stored in vital tissues during periods of starvation (50, 7'0). Thet decrease in resting metabolic demased sympathetic rate duringsevere tmdernutitionismost likely a result of, nervous activity (53) and thyroid hormone -function f28)1~ Several Jnvestigators
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.(31,45,70) have ~uggestedthat ~tbreduced,restingMietabulk rate seen during severe caloric~restrictio1~(5800 kealaday-I [3349 kJ]) may act to inhibit successful I weight loss. Some investigators have .shown that endurane-e exercise during caloric resn-iction may prevent a decline In relative (expressed per kg fat frees mass) resting metabolic rate. (9+011, 5 1, 56: 63), while othms have reported no effect of exerciseon maintainingrelati~e~estingmetabolicrate~duringcaloric atstriction (43,45, 69)' The vari~onsseen in -theeffect .of exercise on resting metabolic rate during caloric .restriction may be a function a!€the sevetity of .caloric restriction applied. In general, w e r e calmic xestri-ction limi@the impact that exercise may exert -on, maintainzing -relative =sting metabolic m e (43,45,69). H m v e ~Mwle , et aL (63) have s h m "thatd 33% w i ~ c t i m ~~i nl a t i v eresting metabolic rate induoed by 2 weeks ~f~ttevere (580 ~kcaltday-'12093 caloric restriction could be ! r e d"bya 2-week daj1y exierci9e (60% +0max)regimen that results in an kcrease in fat free mas. During mild to moderate caloric restriction, exercise has been shown to maintain relative resting metabvlic rate.zin 'both humans (51,t;563 and animals (9, 11). It would ,thewfme appear t h a the degreeof caloric "restictiot~affects the apability of m a d s e to reverse the demase$in relative resting metabolic rate induced by defiiits in energy intake. Additionzlly,*thelength of exmcise mining may have m impact m resting metabolic "rate d d n g energy restriction. Ballor et 81. f9) mated tha in raw~theeffects of exercise in attenudeereases in "re"l?~dve resting me@xboiic mte during caloric te3triction were not statistically siflcant until the 10th 1k*oftraining. While undernutrition results in a decrease in resting metabulie rate, overnnMon a w e s an increase in 'both ratingmetabolic rate and~tkm"1c effect of feeding (6, 48, 49, 85, 99, 100).~.Aside from theA M o n s increase in energy expenditure a s ~ i a k Wlth d ,~emetabolic processing 0%overfeedig, sympathetic ner~ousraaivity(53) ;mnd thymid hm@neTfmctiorl (29) are increased during periods mf mmutri.eiori~Thesaltor8tion in. resting metabolic rate and themic ovmtftrition may be influenced by mch factors effect of Teeding as a ~emlt~rsf BS d i a r y mmpmition, carrentenergy stores the body, 8d heredity (5, 85, " 100). .' Bjrnmrop and Sj4;9.osnwni"16j indicate $hat hm'ans have ~onilja limited aM1izy to'icdnveft exc& dietary iearbohydrrzPtr: Ro fat iztia de now, fatty acid as a remit acuteiemess intake of carbohydrate is most effectively ~prhesis,~and and increasingresting giumse oxidation. handled by maximizing ,glycogen Ingestiorh, df a asingl~large (500 g) mrbohyirate imeal results -in maximizing muscle glycogen storage and increasing the resting rate of carbohydrate oxidation while decmsing *therateof fat metabolism (3)' The inorease in carbohydrate oxidation is mediated by an increase in sympathetic nervous system activity, atmmnting for as mmh as: 3040 offthe increased glmcose-indud thennogenesis
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Influence of Diet and-Egemr'$&/ I
r&titr&*~~gen.~tonmptieii~msared~d'~lrin"g~th~i"gh ~fa&diwmd~da&gI a controhdiet fed;tmtheknbji?'ctWlNeePprkr toebeginffing$he leetogeni'c d i e They suggestithat thisirt4sulbin lig~rbf~theysignificPant reductiotliimhole-body glacose oxidationMdemonstraZes the vbody'mbility To adapt overallvtnetabolism to the I prevailingrenergy substrate conditions in order to sparercarbohydrate. , D i e t w compositiontmay aiso~influencdgenergyexpenditure t h b m h its inlpact on thermic effect of activity. Increasedienergy intake of fat atzthe~xpense :influenee dne's abilitya'to perfomr, at higher wmercise of ~c&bohydrate*;,may intirhsities~Duriflgmild'tomoderate intensity exercise (700/ V02max)~however,carbllydmtB ~ ;serves aspthe primary exercise.energy ~ s o ~ r c d r ~ :.*;+ ~dy, , r;a,'-l~z$ , * J B X &hi*$ .- 14 Undert.such exercise con"ditions2jstudiewha~kPdentdn~&e&~th~md~ced dietmy8carbohydratesconsumption ( 9 3 3 % 4totalrmergy vs'fromwrbohydrate) signifiantly decreases,,exercise time"aio faggueu(n13, 24,~80) %It%& a result of significant reductions.inmuscle glycogen stores prbr tmxercise.-Tj52+80). FuW# research &$neededtordetermine the minimum level of dietary cmbdhydrate that e )ex will adequately support high intensity endurance exercise.
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:* 3 &er0ise5~pose~~~bot!h (single ,bout$and.chromc (long-term%@&hgjjE3ffect9 on oV&dl *energyexpenditure in%humans.The :most obvims dercise effec0 oh ener=:expenditurwis-through+tRe thermic effect of activity. The greaterethe energy~outputthrough;lpurposeful physical activitypflhe greater-the overall daily energpxpendituiiejBouchard et al. (22) recently reported a significant reductiod percent body fat in~ubjectsWho were fed a constant energy !days while also exercising 6 days a week (106 min daily) at a erate (55% VOpmax)intensity. Several more clinically oriented investigations 4 1,51,101) have also shown, in both men and women, that regular endurance.
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gations studfi~guhe'effectsfe%rcised8Modywei-gh;t: induces only modest changes in total bodyeweight o s s , ~ fat ~ f mass may be greater than the loss of total body! ch cases~assessingexercise effectiveness by total body weight may mass loss. While dietary * z during weight loss. of an increased metabolic response &WatfsingletabmrC of, cently termed excess postexercise o~gen4jcunsumption,*wi: een established (30). Unfortunately, research-in this area'ffas to fully describe the phenomenon. Studies have shown that the duratior of %
EPOC may vary from W to 24 hm padtexmcker, A ~ r e w bresting g metaMfc rate arrywhm f m 1 to 25% (8,14,23~30,36:J9,5% 66: 864 100). A~rrumber of methodological variations (subjeetfimesslw??l,'type andintrnity of metxis6 measurement period, meals taken dming m & m e n t period) may asconnt, 8t feast in paafor the disparity in metabolic r e d B seen among these investigatims~ Amonthe more recent.invmtigations, it appears tEr;et the bulk of an EPOC period occurs within the first hour following exercise,.and that the EPOC tends f@ be greater with imemde4cerCise intensity (>70% V02max)andduratifm (>60 min) (23, 39-86), While the totalxenergyexpaditme #ofEPOC (0.7-71.7 kcal [T3300 W]) from a single exercise bout r n a ~ b eminor, when cms?dered Mpm of a regular exercise regimen tkiv energy odtpat 014%time: m I d help to maintain i atis energy balance* The substratesource of thiskrea~ededergyexpendinrrefo~Tdgemci3e dep&dsion exercise4atensity atK1 darat?on*Several imestigams Rave s R W a significant reduction in the respiratory q.&ent" faIlowing~.ex~~ise,~~ttre~by indicating #hcremedfat dxidation ~(8,14, 39, #58+100). Thei@edudimin the post&efcise respiratorg!q ~ i ~diltectljr ~ i related-to s the durztfon rrnd irytmslty of the exercise bout, Vigorous +J70%% q ~ r n a x exercise ) of extended'dt~ation (>60 min) depletes m~scleiglymgenand theley q a i ~ an s imreee in fat oxidation to continue suppIying exercise e n ~ ; ~ i f ? r p n * c e 8 ~ of a t fexwcise, m fatty acid levels may mairr*elevatedfor up to 2 4 W posmercise(58);ind this diminished glucose utilization postexercise allows more exbgemus glucose to be used for the repletion of muscular,glycogen (39) , ,I * The physiologic mechanisms resulting in EPOC have not kendetermined, though resynthesis of a:de"n(rsimrriphsphate, creatine p b s ~ W v j ~ p t e ! and in, glycogen in skeletal muscle is certainly a part 6T the mrly campo&nt bf EPOC, Recent -studiesby Weststrate and Wautvast (1mshow that the increasein restirrg met&bolicrate seenlfollowing~t;xhaustive trycling exercise c m be red&ed when the ,extsrcise is+pwededrby4days of pragre&ve carbohydrate overfeeding. of EPOC Ac~wdingto the anthorsr these findings indicate t M a large smpment~ may be related to energy expended to refill mnscle.glycogen stores. ,Gaesser an& Brook$(38) have gated that my -fat:torsdnflutncingmirocfmndrial axygen consumption will contribute to EPUC. Therefore Stlch FWdrs as metirbolic h m m e (catecholamines,thyroxinei glu~:rxmicoids"$ cont~r?nWaPIma calcium ion concentration, sodium pump acthity, and W y Pempmtm? will hrfluence EPOG, Newsholrne (64)has also made %*casefor-stlbstrafe cycling (interconversion of metabolic intermediates which ~ 1 1 for ~ greater s en~yhe ex&se sensitivity) 8s a possible compomt of EPOC, A~equiva~ent-Bbsolute worklottds, EPOC seems to be reduced itr tmimd swbjem (42):This wmfd s e h Iogical since trained .d: subjects have a gerrerallyt*depressed~ 3overall metabolic - responses to a given *mercise:morkloMwhen compared to mtrained' ~ub$?cts. Sem1"~investigfftor~~ employittg both lungitudinat (54,?56) end cross sectimal>(73,74?75,78, 93, 94) mthods, have shown TRat mmpzued'to the m ~ a i n e d ~ ~ ~ strretabolic ting rate issincreased as a resalt of-clwonic end@rm1 exercise training, Poehlman et aI. C75) *identifiedpr linearrelations2ff between f r ~ m a find. k relative resting metabolh rate in grrPung~males, More-;recently, Poehlman qdbcollm@esr have dmonstr*d that entiuram exercise trttinirfg (as defined.& VOzmax) am'ounts&x a small bubsignificant prticrtuof thC variatrdrr in resting rnetaibolic rate in nmobae older men (73) and rronobek you@femaIes
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C78.751The.8 ~ t h o rdo s .cautim that vhile these-" ~ m ~ ~sd-te' t i m ~a rel8tWishily between a 'high level ,of endurance training and increased resting metabolicrate, it doe$mtnecessad1ydmo~te~icause-and-~fect~relationship, since the influence sf training on both resting meta'bolic rate and V0,max may e dependent (72, 79). he level of endurance training may sign~~cantly affect the ability of endurance exercise to influence resting metabolic rate. Tremblay et ak. (93) heamred r&ng metabolic7rate in wntrained, mmlerately mained 7{;5-L48 8hrs of vigorous %&ly exercise), and highly traine"B (12-16 hrs of vigorous Weekly exercise) yaung male subjects. Theif findings showed ~-thal?*relative;7esting metabolic rate was significantly increased in the highly trained subjeetsdwhile there wasym dgnificant diffeence in relativelrestbg metabolic between the untrained and moderately trained' subjects. Other investigators have fa?led to show a difference ih restifig imetabolic rate as a result of endurance &&cise mining. Binghm~&%l.*(15) failledm find a+difference in basal mtabolie rate, overnight metabolicb-rate, or sleeping metabolic .rate in subjects follopling 7 weeks of endurance#+(.IjealWj@)~exacise trainingirVnforhmately, the study popnlation m 3 rather smMl (N=6) ,and the m a n relative-.~0~rnax posttraining (-5 1 ml.k.gihin-') might be consideredmly as rmodemtely trained. Schwlz et al. 70 x ml-kg-l.ain:') and-antmined y m g mdes in a respiratorychamber and found no differbetween the tW groups. The tests were cond1etedQdays posttraining while feeding;subjects a weight rr&ntenmee diet which, in the case of the trained subjects, was considerably less food than normally m~sumed.. ' a , ; 'r Schulz et al. noted it is possible tfMtre2ewted resting mdtablic fate ~ 4 t h exrdise training may be psent~onlytwwrhigh Iwels of ia'efi~ityittfematched withiphigh caloric in-take. The elevated%re$tingmetabolic Batemoted 4n Xghly mined individuals might therefore be a short-term adautation to thaknhanced energyturnover assoli~ted'withkhr0nic physicdl training: The mdy of Tremblay et al. (94) might tmd to &pport this hypothesis, as they showala 6.6% drop in resting imet#bolk rate of highly trained subjeets following 3adaymof dettaining! -, %.The~mechanisrn4qvwhichfrolonged endurance exercise6 training might inckase resting metabolic rate is notclear; hasrtewr~Poehlfmn&all-(75)duggest that restleg metabolic rate-may'be affected b3.adHi'gh'icaloric Imntwer (inheased energy intake and expenditure) in a state a$ energy balance. .am3 might be e~plainedin part via substratecyding,dncea high volume of enetflnx through a metabolic system would andoubtedly- require lelevated enzyme activity. An additional factor to conside%tmi~htbe afl acmm~lative~ EPOC ~ieffeet,since exercise intmsi* duration,: and ?reqbenty m e 811 increased in:l&hly ttrained mbjects, end since themic effect of meals,&iken.pmtexercise mwy be in-eased (58, 61, 87):. 8 ..a -, k R d t s from m e a l hwst+@ors ,indicatewW.a%4ll;g1e 'boat of mil$ to mckltx'ate-imtene, e ~ d s exerts e a "pt3kntiting eff%tron tWfElieieffect of feeding (58,62, 87, '88, 89, ,JfOO)k This effect seems most pronounced in lean individuiPls and,h@"%e6i te~61tof&creai3ed sefisitivitqto thennogenic hormones in these tindilriduals wb,comparedto~abese&%jects(87, 88). AdditioWlIy; icfre t h i n g of'the exerei%*relative to*thBMteal&ky influence themagnitude of the enhancement of t h i c effecb&feaing. "Segal et al. (88') showed that kclean
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subjects the thermic effect of feeding was most pronounced when the meal was consumed prior to exercise, while in obese subjects the thermic effect of feeding was greatest when the meal was consumed after exercise. The enhanced thermic effect of feeding in the obese postexercise, when compared to the lean subjects, may be a result of both an increase in glucose uptake by skeletal muscle as a result of exercise and an increase in thermogenic hormone levels and sympathetic nervous activity (88). ' Contrary to the above findings, several investigators have found exercise to have little if any enhancing effect on thermic effect of feeding (12, 25, 26, 98). Several methodological factors could explain some of the variation seen in the results of the various studies in this area. Welle (98) noted that few studies which have fed meals of less than 900 kcal(3,767 kJ) have seen enhanced thermic effect of feeding associated with exercise. Some studies that have failed to show an enhanced thermic effect of feeding with exercise measured oxygen consumption for a short time (60 min or less) (12, 26) or had brief sampling periods (2 min) over several hours (25). Additionally, exercise duration has varied substantially in these studies. Several studies failing to show increased thermic effect of feeding with exercise have used short (15 min or less), intermittent exercise bouts (25, 98), while many studies demonstrating a potentiating effect of exercise on thermic effect of feeding have used prolonged (30-80 min), continuous exercise bouts (58,62,88,89, 100). It is also important to recall that there is a significant degree of inconsistency and conflicting results in the general area of thermic effect of feeding research. Lack of standardized protocols and incompletely described methods have resulted in a wide variety of answers to the various research questions related to thermic effect of feeding (17). While still the topic of some debate, it appears that chronic exercise training which results in a high degree of fitness tends to decrease thermic effect of feeding. In their cross-sectional study of 28 young male subjects covering wide ranges in maximal aerobic capabilities (defined both by VOzmax and level of endurance training), Poehlman et al. (75) demonstrated a curvilinear relationship between V02max and thermic effect of feeding. Thermic effect of feeding was highest in moderately trained individuals whereas it was lower in the highly trained and untrained, This curvilinear response may explain why some studies have shown a linear relationship of V02max and thermic effect of feeding (44), especially if the sample size or range of fitness levels was limited. It is possible that in the untrained a reduced sensitivity to insulin may be the cause of the decreased thermic effect of feeding;while in the highly trained a decreased sympathetic nervous activity as a result of chronic exercise training may result in a decreased thermic effect of feeding (75). It should also be recalled that highly trained individuals have an elevated resting metabolic rate, which might tend to mask a portion of the facultative component of thermic effect of feeding. Finally, a strong genetic component to thermic effect of feeding has been demonstrated that could also influence individual response in this measurement (77).
Considerations for Maintaining Energy Balance Maintaining a healthy body weight has been recognized as an imp a healthy lifestyle (92). Leanrindividuals are at lower risk for c disea~e,~diabetes, hypertension, and stroke. Compared to the obese, lean individa-
Influence of Diet and~Exercl;iee/ 111
- d si show1sgreatm~emitiYity&in b m ~ & b 6 . H ~ r W ~ n e ~ 8 eand-: s p dthtertf~re; ~ ~ e an enhane&kapacity to'prmessdsmrces &ofenergy~:in"~th@ fa~ehof~~arious metabolic demandsibsince botlndictaryq~antityand coi4ipbsit~onas .pell~%Hracuteand %hroniciiexercisetrainingaaffeat allifacetsoftdaily energy e~pendituliepitseems importabt,to consider thme dietary,andlexcrcise effectscthat might seem most appr~priate~ain attaining and/ortmaintainingr.energy balance. a ~~,k o B, , a Sin~e:~in6reased~physical dactivitya-as dq4result+ of purposeful eWoist,will Jd~rease~themicieffect of activity,d would4seem logical that+regzuI;riif&d~~$n~e eeruercise~~ollld play aneimportant~roleaiinrrnaintainingenergpbalanch Regular physical activity may also influence ca1ofic:intake. In,a study of malt Indian :Roy, and Mitras(60) - m e d thaLc8loric intakeaincrdsed in rnillwork:ers~tMayer, those@vorkrsi whose~miyityfell.bebw&8.r: :normal! Zone' ', (defined3asfmediuh to nlightmcMty work), *For ~ w o r k e r ~ ~ ~ w ~ e : : a c tdevels i v i t y were at, or: abovd the nornralaone, mlori-o intzke closelyspml.leled.rcalo~&ex~endft&6r~ This is anrrlogous*totanihalmodels, iniwhich-activity restriction.i+ithout caloriwdestris$4 i$t >%+*,, a 8 ?,id tion results in overmting,and obesity (59). -, pi"dditiohally,j intense physical .trainin@kommonlys&duves ~esptfnseiof dinfinished appetitq which may~occuwtsaresult ofithefelmatedbodptern~erarn avsociated with thisxtype of.trAning (7); Thoughfassociatedmore-&th.Goderate to high levels-of physical fitness, th&&ffectsof exercise on restinghetdbolic~rate and thermic effectsf feeding mustdalso be considered asyadditional meansby , : which regula~exercise could help maintain -energy$balance. 1nterestingly:ithe overall effeetivetiesaof .exercise in dedreahifig adiposity lmaynbe gender dependenb ~Std?Iiessinvestigaingt h e effektivenkssmf a.20-week aerobiaexerciserprogram .on body ~Tarnt3ssmd aadipade*tibu&fun&'on4ndtedtthat males~demmstrated,~~ignificant reduction incbody+w&ght+"fa-t'idass,petment:ifat, and*fatIIcellxweightswhile, fem'ales ,sh+owed,:ito significant changerbr4hese parametets ,g(29,t 92)t:r Additionallyj*,while training increased epr'rrephrinrn stimfilafed rlfpolysis~im both males and-femrrles, ,the inkrerra-ivasa-considerablP more ,pronounced in males (+66%) than in females (+46%). The results of these studiessuggest that, while both males,and,femalesmay lose fatmass withregular enduranse exercise training, males may be+moresensitive to the:effects of exercise on adiposity than females. a Pfbb ".' t t. Y hjt ,* A@the primary soume of:energy, utilized by athe eentralrfftervo%s system, * $-to f 2: nf ~BgMl u t rmal ~ & d u l l a : r a ~ d ~ ~ ~ d ~ B l o d d ~ ~ l P s , ~ ~ p ~ l i i &in pHysialagical-fudCrimi.i.Fla~,i'(33)~bijted, in light of the hum%fl'~ratw~lirnited abilitydo storeacarbokrfrdrat&* ' 'it -would s6em that$biokogical %volutimt-would have a been~colnpelled-to de~lopkmech%nismsgiving highei%priority>to the presmatibmf carbohydrate:baIante" (p. 305). The body therefore seeks to attain an appropriate carbohydrate~;balance~ throrgh dietary intake. In: Western societie~sverthapast~50 yemt thericontenbt9f fat in the typical diet has increased ap~r~~i~dtely+20%~to&level Where it constitutes 43% of total energy consumed (40)r"Undert&ese+dietarjrcond"lTion9#consumptionof f d ~ in d an' effort to&sfin:taih barbehydrate ba'lance cawlead to a wnsumption of dietary fat beyond Metabolib need, which rtltimatElyleads to an%8ccumulationof body fat and possible onset 4rr4i 4 9 :%a ~i x", , of obesity, b i j r Ix matt3m ) s A m a a~ a ~ ~ & n a . ' s o d ~ ~ ~ ~ o 9 ~ r l i ~ ~ @ e ~ @ . M 1 ~ @ emdin in & e a ~ ~ ~ t t j . ~ d u n dfile~e0iRp~sitia:fi"df ifio~~ ~W~di~cnrus~~a1l~1trthe composition a f theTue"ra~idizedJTo~11ustrate thisXpdntihe irstes that the food
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quotient (ratio of carbon dioxide formed to oxygen utilized during combustion of the diet) of the typical western diet (total energy partition: 45% carbohydrate, 40% fat, 15% protein) is 0.85, while the respiratory quotient following an overnight fast is 0.82. If energy balance is to be maintained over the course of the day, the respiratory quotient must equal the food quotient. If the daily respiratory quotient exceeds the daily food quotient, a greater proportion of carbohydrate was oxidized, resulting in an overall carbohydrate deficit. If carbohydrate balance is to be reestablished on the typical mixed diet, food will be consumed in amounts exceeding actual energy expenditure, with the excess energy derived from fat being stored. It is therefore important to maintain an equilibrium between dietary intake of fat and oxidation of fat through activity. Such a condition may be achieved by either limiting fat intake (increasing the dietary food quotient by consuming a high carbohydrate diet), increasing activity of sufficient intensity and duration (mild to moderate endurance type exercise which tends to elicit lower respiratory quotients) to increase fat oxidation, or combining both factors. In final consideration of the reviewed research, it would seem that a balanced diet sufficient in protein, low in fat (530% total energy), and rich in complex carbohydrate may be the most appropriate for apparently healthy humans (96). Such a diet should be complemented by regular endurance exercise of an intensity and duration appropriate for the physical capabilities of the individual. If weight loss is desired, dietary restriction should come mostly from fat sources and should not be severe, thereby reducing the risk of decreasing resting metabolic rate through severe undemutrition. Prolonged exercise of mild to moderate intensity would also be a logical component of any weight loss regimen, as it would add to the overall energy deficit while serving to maintain resting metabolic rate in a state of undernutrition (37, 51, 63). The increased energy expenditure through exercise would also decrease the magnitude of the energy deficit required from caloric restriction in an attempt to achieve a healthy body weight.
The flux of energy through the metabolic systems of the human is a dynamic, multifaceted process. Variations in energy intake, physical activity, environmental factors, and genetic background make the study of human energy expenditure a most complex task. In considering the effects of diet and exercise on energy expenditure, one must understand how they influence each of the component parts of total energy expenditure. Total dietary content influences resting metabolic rate, resulting in a decreased resting metabolic rate during undernutrition and an increased resting metabolic rate with overfeeding. These dietary-induced changes in resting metabolic rate result from alterations in sympathetic nervous system activity and metabolic hormone function. Dietary composition may affect energy expenditure. The body maintains precise metabolic control of carbohydrate and protein by altering oxidation rates of these nutrients, since their storage capacity in the body is limited. Less stringent control is required of fat, since excess dietary fat is readily stored at minimal metabolic expense. Excess intake of fat not only leads
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10. Ballor, D.L., and R.E. Keesey. A meta-analysis of the factors affecting exerciseinduced changes in body mass, fat mass, and fat-free mass in males and females. Int. J. Obes. (in press). 11. Ballor, D.L., L.J. Tommerup, D.P. Thomas, D.B. Smith, and R.E. Keesey. Exercise training attenuates diet-induced reduction in metabolic rate. J. Appl. Physiol. 68:2612-2617, 1990. 12. Belko, A.Z., T.F. Barbieri, and E.C. Wong. Effect of energy and protein intake and exercise intensity on the thermic effect of food. Am. J. Clin. Nutr. 43:863-869, 1986. 13. Bergstrom, J., L. Hermansen, E. Hultman, and B. Saltin. Diet, muscle glycogen, and physical performance. Acta Physiol. Scand. 7 1:140-150, 1967. 14. Bielinski, R., Y. Schutz, and E. Jequier. Energy metabolism during postexercise recovery in man. Am. J. Clin. Nutr. 42:69-82, 1985. 15. Bingham, S.A., G.R. Goldberg, W.A. Coward, A.M. Prentice, and J.H. Cummings. The effect of exercise and improved physical fitness on basal metabolic rate. Br. J. Nutr. 61:155-173, 1989. 16. Bjomtrop, P., and L. Sjostrom. Carbohydrate storage in man: Speculations and some quantitative considerations. Metabolism 27(Suppl. 2): 1853-1865, 1978. 17. Blondheim, S.H., B. Mendelson, P. Hashkes, and R. Aranne. Dietary thermogenesis: Why the conflicting results? In Recent Advances in Obesity Research: V , E.M. Berry, S.H. Blondheim, H.E. Eliahou, and E. Shafrir (Eds.), London: John Libbey & Co., Ltd., 1987, pp. 151-154. 18. Bogardus, C., S. Lillioja, E. Ravussin, W. Abbott, J.K. Zawadzki, A. Young, W.C. Knowler, R. Jacobowitz, and P.P. Moll. Familial dependence of the resting metabolic rate. N. Engl. J. Med. 315:96-100, 1986. 19. Bouchard, C. Heredity and the path to overweight and obesity. Med. Sci. Sports Exerc. 23:285-291, 1991. 20. Bouchard, C., A. Tremblay, J-P. Despres, A. Nadeau, P.J. Lupien, G. Theriault, J. Dussault, S. Moorjani, S. Pinault, and G. Fournier. The response to long-term overfeeding in identical twins. N. Engl. J , Med. 322:1477-1482, 1990. 21. Bouchard, C., A. Tremblay, A. Nadeau, J-P. Despres, G. Theriault, M.R. Boulay, G. Lortie, C. Leblanc, and G. Foumier. Genetic effect in resting and exercise metabolic rates. Metabolism 38:364-370, 1989. 22. Bouchard, C., A. Tremblay, A. Nadeau, J. Dussault, J-P. Despres, G. Theriault, P. Lupien, 0. Serresse, M. Boulay, and G. Foumier. Long term exercise training with constant energy intake. 1. Effect on body composition and selected metabolic variables. Int. J. Obes. 1457-73, 1990. 23. Brehm, B.A., and B. Gutin. Recovery energy expenditure for steady state exercise in runners and nonexercisers. Med. Sci. Sports Exerc. 18:205-210, 1986. 24. Christensen, E.H., and 0. Hansen. Zur methodik der respiratorischen quotientbestimmung in Ruhe und bei Arbeit 111 [Nourishment and the capability to work]. Arbeits Faehigheit Emaehmng. Scand. Arch. 81:160-171, 1939. 25. Dagenais, G.R., A. Oriol, and M. McGregor. Hemodynamic effects of carbohydrate and protein meals in man: Rest and exercise. J. Appl. Physiol. 21: 1157-1162, 1966. 26. DaIIosso, H.M., and W.P.T. James. Whole-body calorimetry in adult men: 2. The interaction of exercise and over-feeding on the thermic effect of a meal. Br. J. Nutr. 52:65-72, 1984. 27. Danforth, Jr., E. Diet and obesity. Am. J. Clin. Nutr. 41:1132-1145, 1985. 28. Danforth, Jr., E. The role of thyroid hormones and insulin in the regulation of energy metabolism. Am. J. Clin. Nutr. 38:1006-1017, 1983.
!35-239, 1' energy reql 1935. ~d W.M. B weight los
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48. Jequier, E. Carbohydrates: Energetics and performance. Nutr. Reviews 44:55-59, 1986. 49. Jequier, E., and Y. Schutz. Long-term measurements of energy expenditure in humans using a respiration chamber. Am. J. Clin. Nutr. 38:989-998, 1983. 50. Keys, A,, J. Brozek, A. Henshel, 0. Mickelson, and H.L. Taylor. The Biology of Human Starvation, Vol 1. Minneapolis: University of Minnesota Press, 1950. 51. Kiem, N.L., T.F. Barbieri, M.D. Van Loan, and B.L. Anderson. Energy expenditure and physical performance in overweight women: Response to training with and without caloric restriction. Metabolism 39:651-656, 1990. 52. Kirwan, J.P., D.L. Costill, J.B. Mitchell, J.A. Hournard, M.G. Flynn, W.J. Fink, and J.D. Beltz. Carbohydrate balance in competitive runners during successive days of intense training. J. Appl. Physiol. 65:2601-2606, 1988. 53. Landsberg, L., and J.B. Young. The role of the sympathetic nervous system and catecholamines in the regulation of energy expenditure. Am. J. Clin. Nutr. 38:10181024, 1983. 54. Lawson, S., J.D. Webster, P.J. Pacy, and J.S. Garrow. Effect of a 10 week aerobic programme on metabolic rate, body composition and fitness in lean sedentary females. Br. J. Clin. Pract. 41684-688, 1987. 55. Lean, M.E.J., and W.P.T. James. Metabolic effects of isoenergetic nutrient exchange over 24 hours in reIation to obesity in women. Int. J . Ohes. 12: 15-27, 1988. 56. Lennon, D., F. Nagle, F. Stratman, E. Shrago, and S. Dennis. Diet and exercise training effects in resting metabolic rate. Int. .I. Obes. 9:39-47, 1985. 57. Lissner, L., D.A. Levitsky, B.J. Strupp, H.J. Kalkwarf, and D.A. Roe. Dietary fat Clin. . Nutr. 46386and the regulation of energy intake in human subjects. Am. .I 892, 1987. 58. Maehlum, S., M. Grandmontagne, E.A. Newsholme, and O.M. Sejersted. Magnitude and duration of excess postexercise oxygen consumption in healthy young adults. Metabolism 3.5425-429, 1986. 59. Mayer, J., and D.W. Thomas. Regulation of food intake and obesity. Science 156:328337, 1967. 60. Mayer, J., P. Roy, and K.P. Mitra. Relation between calorie intake, body weight, and physical work: Studies in an industrial male population in West Bengal. Am. J. Clin. Nutr. 4:169-175, 1956. 61. McNeill, G., A.C. Bruce, A. Ralph, and W.P.T. James. Inter-individual differences in fasting nutrient oxidation and the influence of diet composition. Int. .I. Ohes. 12:455-463, 1988. 62. Miller, D.S., P. Mumford, and M.J. Stock. Gluttony 2: Thermogenesis in overeating man. Am. J. Clin. Nutr. 20: 1223-1229, 1967. 63. Mole, P.A., J.S. Stem, C.L. Schultz, E.M. Bemauer, and B.J. Holcomb. Exercise reverses depressed metabolic rate produced by severe caloric restriction. Med. Sci. Sports Exerc. 21:29-33, 1989. 64. Newsholme, E.A. The interrelationship between metabolic regulation, weight control, and obesity. Proc. Nutr. Soc. 41: 183-191, 1982. 65. Otton, M.H., G. Hennemann, R. Docter, and T.J. Visser. The role of dietary fat in peripheral thyroid hormone metabolism. Mefaholism 29:930-935, 1980. 66. Passmore, R., and R.E. Johnson. Some metabolic changes following prolonged moderate exercise. Metabolism 9:452-456, 1960.
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