December 1992: 454-462

Macronutrient Needs in the Elderly Vernon R. Young, Ph.D, D.Sc.

introduction

This short review will highlight some of the significant research and practical issues related to protein and energy metabolism in the elderly as well as quantification of macronutrient needs in this population. We begin with a summary of the components of the energy requirement and will explore whether there are significant age-related factors, relative to energy metabolism and requirements of younger adults, that are important to consider. Current estimates by various expert groups of the energy requirements in the elderly will be surveyed before exploring the significance of the dietary source of the principal energy-yielding substrates. A short account of the underlying metabolic basis for the two components of the protein need will precede an overview of current estimates of proteidamino acid requirements and dietary allowances for the elderly. Despite space limitations, it is hoped that the following will be a reasonably balanced evaluation of what is known about the macronutrient requirements in older people and will provide suggestions for further research. Components of the Energy Requirement

The energy requirement of an individual is represented by the energy balance equation, which is elaborated in Table 1. Because recent national'.2 and international3 estimates of energy needs have been derived from predictions of energy expenditure, rather than from measures of energy intake, which was the approach used earlier,4 it is worthwhile to emphasize here major components of the energy requirement. These include obligatory thermogenesis, consisting of the basal metabolic rate (BMR) and the thermic effect of food. In addition, facultative thermogenesis accounts for the other Dr. Young is Professor of Nutritional Biochemistry at the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.

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major aspect of energy expenditure where, for normal living conditions, the energy transformations associated with physical activity and diet-induced thermogenesis are the principal factors. Hence, with reference to the energy needs in elderly persons, two important questions should be raised: 1) How large are these various components of the daily energy expenditure? and 2) Do they change, and, if so, why, during the progression of the adult years? An approximate distribution of the daily energy expenditure in a relatively sedentary adult is shown in Figure 1, indicating that basal metabolism might well account for about 60% or more of the daily energy flux. Various factors, including familial and genetic influences; nutritional, metabolic, and disease conditions; and gender and body composition determine the BMR,' which is reduced in the elderly (Table 2). This decline is due largely to the agerelated fall in lean body mass,I2-l4 which probably results mainly from the erosion of muscle mas^,^'-^' because BMR in the elderly is either unchanged or only slightly lower than in younger adults when expressed in relation to lean body mass, cell mass, or fat-free mass. The small although statistically significant difference in BMR (expressed per unit of fat-free mass or cell mass) that has been reported between younger adults and elderly subjects'&I2 is of biological interest, of course, and may be related to the diminished size of the skeletal musculature.13 This may account for up to about 30% of the BMR in the healthy young adult." However, this difference does not seem to be of major quantitative importance in establishing the prevailing daily energy requirement, provided that the predictions of BMR, based on body weight, include an age factor, as is true for the 1985 FAO/WHO/UNU3 procedure for estimating energy needs. The other component of obligatory thermogenesis is the thermic effect of food (TEF), which is due to the energy transformations required for the ingestion, digestion, absorption, processing, and storage of the energy-yielding nutrients. The energy costs of the T E F vary according to the immediate

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Table 1. The Energy Balance Equation: Energy stored

=

energy intake - energy expenditure

Energy Intake Metabolic food energy

Energy Expenditure (Thermogenesis) Obligatory thermogenesis Basal metabolic rate Thermic effect of food Facultative thermogenesis Physical activity Nonshivering thermogenesis Diet-induced thermogenesis

metabolic fate of these nutrients,” whereas the facultative component of dietary thermogenesis is due to metabolic cycle activity and to activation of the sympathetic nervous system (SNS). Because changes in the activity and responsiveness of the SNS occur with advancing old age,1sL23the results of various investigations concerned with the effects of food and diet on human thermogenesis deserve review. The findings from a number of acute metabolic studies, presented in Table 3, show a somewhat variable outcome from different experiments. In general, there is a smaller change in energy expenditure in the older person following a test meal or series of meals, but the difference between younger and older adults is not large. The size, frequency, and composition of meals also affect the TEF,30 making it difficult to draw a definitive conclusion concerning the possible impact of aging. Furthermore, the energetic response to meal ingestion might be significant when the concern is for longterm regulation of energy balance, particularly if a difference between young and older subjects does

Approximate Distribution of Daily Energy Expenditure in an Adult

-* m

8 Y

Y

>.

: C

W

Figure 1. An approximate distribution of the major components of daily energy expenditure in a relatively sedentary adult.

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not elicit a compensatory change in the regulation of energy intake. On the basis of the available findings, however, a reasonable estimation of the daily energy requirement in younger and older adults would not appear to depend to any large extent on an age-related consideration of the thermogenesis due to meal ingestion. However, and particularly with regard to the balance of body energy, it is important to learn whether there are any long-term metabolic studies that might support this conclusion. A study currently under way in our laboratories appears to be the only one available that addresses this issue, in particular with respect to assessing the energy needs of the elderly. Hence, based on recent studies by, for example, Ravussin et a ~ and ~ Rob’ erts et al.32that confirm and extend earlier but usually less complete investigations of the components of energy expenditure and b a l a n ~ e , ~ ~it- appears ~’ that diet-induced thermogenesis in young adults is only partially activated when excessive energy intakes are consumed over a period of several weeks. It is evident that there is a limited capacity to dissipate excess energy as heat, and so the important issue is whether this capacity to adjust to changes in energy intake is altered in a quantitative way during aging. Based on our preliminary findings (Table 4), we tentatively conclude that changes in body weight and composition, resting energy expenditure (REE), and the TEF are quantitatively similar in both older and younger adults when they receive a diet supplying approximately 1000 kcal in excess of maintenance energy needs for a period of three weeks. Although the data are not shown here, the same conclusion also applies to the responses of energy metabolism when energy intakes are restricted to about 800 kcal less than maintenance needs (unpublished data). From this admittedly limited data, it may be concluded that diet-induced thermogenesis is quantitatively similar in younger and older subjects, at least for the range of energy intakes we have investigated. It appears that there are no profound differences in thermogenic responses to meals that should be considered when estimating the intake required to maintain energy balance over the short term. This does not mean, however, that this is also true for the longer term; there is an urgent need to explore the consequences of altered energy intakes both above and below those that we have investigated (i.e., either -800 or + 1000 kcal from maintenance) in order to define more completely the relationship between energy intake and the components of energy expenditure in adults of various ages. W a t e 1 - 1 0 has ~ ~ ~emphasized the importance of establishing “dose-response’’ relationships in stud-

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Table 2. A Selected Survey of Studies Concerning Basal Metabolic Rates in Relation to Aging

Basal Metabolic Rate Authors (Ref.)

Young

Old

Comment

Shock et al. (6) 21” 19” No difference when adjusted for body water Keys et al. (7) Decrease of 1-2% per decade between 20 and 75 years Calloway and Zanni (8) 31b 31b No difference per LBM Poehlman et al. (9) 22” 19” No difference per FFW‘ Fukagawa et al. (10) 25” 21” About 10% difference per FFW Vaughan et al. ( 1 1 ) 21” 19” Small difference (-5%) per FFW Roberts and Youngd 24“ 19” Small difference (-7%) per FFW ” kcale kg body wt-’ . day-‘. kcal . kg LBM-’ (LBM = lean body mass). ‘FFW = fat-free weight. Unpublished data. ies of human nutrition, and it is unfortunate that so little of this information is available in most areas of human nutritiodmetabolism. Energy Requirements in the Elderly

Energy requirements in elderly subjects might be considered in reference to the most recent authoritative international statement concerning the energy requirement of adults. In the 1985 report of the FAO/WHO/UNU Expert C o n s ~ l t a t i o nthe , ~ energy requirement is defined as the level of energy intake from food that will balance energy expenditure when the individual has a body size and composition, and level of physical activity, consistent with long-term good health; and that will allow for the maintenance of economically necessary and socially desirable physical activity. In children and

pregnant or lactating women the energy requirement includes the energy needs associated with the deposition of tissue or the secretion of milk at rates consistent with good health.” The FAO/WHO/UNU report3 set or defined this level of energy intake by estimating the energy costs of various factors, expressed in multiples of the BMR. These factors are: 1) the BMR; 2) growth, in the case of the young; 3) physical activity, which is divided into “occupational” and “discretionary” activities; and 4) the TEF. The estimates of energy requirements, for practical purposes, were based on predictions of energy expenditure for various conditions and types of activities and on judgments about what is considered desirable for elderly persons. The maintenance component was taken to be about 1.4 times the BMR for both men and women; when other com-

Table 3. A Summary of Studies Concerned with the Thermogenic Responses to Nutrients and Meals in Young and Older Subjects

Test Conditions Young Old CarbohydratelMixed 100 g oral glucose 8.6” 5.8” 800 kcal high CHO meal 3b 2b 7.1‘ 7.6‘ Mixed meal (25% energy requirement) 8.9” 6.2” 75 g oral glucose Liquid formula: 4 MJ meal 8.3” 5.1” 21d 23” Three meals and 1 snack Protein 9.7‘ 11.9“ 25 g protein (beef, egg white) 60 g protein 0. 17f 0.21‘ ” Percent of energy content of load over 3 hours (old lower than young: p < 0.05). Percent of ingested caloric load over 2 hours (u < 0.001). Percent of ingested energy over 4 hours. Percent of energy intake and energy cost of arousal in calorimeter. ” Percent increase in oxygen consumption over 4.5 hours (u = NS). Increment in energy expenditure (kcal/min) over 6 hours. 456

Authors (Ref.) Golay et al. (24) Schwartz et al. (25) Roberts and Young (unpub.) Bloesch et al. (26) Morgan and York (27) Vaughan et al. (1 1 ) Tuttle et al. (28) Fukagawa et al. (29)

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Table 4. Effect of Overfeeding by 1000 kcal/d for 21 Days on Body Weight and Energy Expenditure in Young and Older Mena Young

Table 6. Comparison of Average Energy Requirements for Healthy Elderly Men, Expressed as Ratio of TEE: REE (according to various authori t ies)

Older

+2.24 & 0.29 Body weight (kg) +2.25 ? 0.4Ib +50 t 41 +46 31 REE (kcal/d) TEF (kcal/d) +I11 29 + 1 1 1 ? 36 Maintenance EE (kcal/d) +168 49 +I42 t 51 a Unpublished, preliminary MIT data of S. Roberts and V. Young. Mean 2 SEM. Differences between groups are not significant.

* *

*

ponents were expressed as a function of BMR, the average daily energy requirement of an elderly person might be approximated at about 1.55-1.75 times the BMR.3 Of course, these are only simple guides. A more thorough estimation of the average energy needs of a group of healthy retired men is shown in Table 5 , where time spent in, and the predicted energy costs of, various physical activities are presented in greater detail. The total daily energy expenditure in these older individuals is, again, assumed to be equivalent to about 1.5 times the BMR. As a general guide, therefore, it appears that various expert groups’-3 have judged the average energy requirement in healthy elderly persons to be about 1.5 times the resting energy expenditure (Table 6). The recent United Kingdom recommendations2 were presented with some justification, although they appear to be consistent with the range of energy intakes reported for various elderly population groups. However, the accuracy of food intake estimates remains a major problem in human nutrition research, and there is increasing evid e n ~ e ~ ’to- suggest ~~ that energy intake data tend to underestimate what is actually consumed. Hence, my colleagues and I have wondered whether these approximations of average energy requirements in the elderly, as proposed by these various authori-

Authority (Ref.)

TEEIREE”

FAO/WHO/UNU (3) -1.51 NRC-FNB (1) - 1 .5b Dept. Health-UK (2) -1.5 MIT (unpub. data; Roberts and Young) -1.75 a Ratio of total daily energy expenditure to resting energy expenditure. For age 5 1 + years.

ties,’-3 are satisfactory. Accordingly, we have begun to measure directly the total daily energy expenditure in free-living young a d ~ l t s and ~ ~ , ~ ~ healthy older men and women4’ using the doubly labeled water neth hod.^^,^^ As shown at the bottom of Table 6, we have determined that the average daily energy expenditure of this elderly sample approximates 1.7 times the BMR. This is lower than expenditures for healthy young adult men, as shown in Figure 2, for whom our determinations of mean energy expenditure are nearly twice the BMR. Hence, these direct determinations of energy expenditure, while differing between the young and old in the expected direction, are considerably higher than prevailing predictions of energy expenditure given by various expert groups.’-3 Our determinations of energy expenditure in young adults, using the doubly labeled water method, generally agree or are consistent with a number of investigations in which daily energy expenditure of free-living persons has been mea~ u r e d . ~However, ’ our studies now raise significant doubt as to whether the FAO/WHO/UNU predictions of the energy costs of physical activities used to estimate total expenditure are valid and/or whether our young adult and elderly study populations are “representative.” Resolving these issues will require careful and extensive investigations of the total daily energy expenditure in different elder-

Table 5. Average Energy Requirement of Healthy, Retired Elderly Mena ~

Hours

kcal

kJ

In bed at 1.0 x BMR 8 430 1810 Occupational activities 0 0 0 Discretionary activities: Socially desirable (3.3 x BMR) 2 355 1490 Household tasks (2.7 x BMR) 1 145 610 Cardiovascular and muscular maintenance (4 x BMR) Y3 70 300 For residual time, energy needs at 1.4 x BMR 12% 960 4020 1960 8200 Total ( = 1.5 X BMR) a From Table 12, p. 77 in FAO/WHO/UNU.3 Average age 75 years, weight 60 kg, height 1.6 m, BMI 23.5; estimated basal metabolic rate: 54 kcal [225 kJ] per hour. Nutrition Reviews, Vol. 50, No. 72

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2.2

***

2.0

w w w

**

1.8

-

1.6

-

I

w w

c

RDA L

I

20

I

I

40

60

I

80

1

100

AGE (years) Figure 2. Energy requirements, expressed as the ratio of total energy expenditure (TEE) to resting energy expenditure (REE) in young adult and elderly men (based on ref. 41) in comparison with the average energy allowances proposed by the US Food and Nutrition Board.’

ly populations, as well as in young adults, under various environmental settings. Source of Energy-Yielding Nutrients Finally, when considering energy needs it is important to question whether the mixture of dietary energy sources used to meet these needs is of metabolic, pathophysiologic, and/or nutritional significance. These are important considerations for several reasons: 1) there is a deterioration of glucose tolerance in aging due to peripheral tissue insulin sensitivity, late insulin secretion, and altered he2) hormone-induced adipatic glucose output;*6 pocyte lipolysis decreases in aging and lipolysis per unit of adipose tissue is lower in older humans than in the young;49and 3) there are positive epidemiologic associations between fat intake and body composition, suggesting that the compoiti ion'^*^' of the diet is an important factor in determining energy balance and body composition. Thus, it is important to inquire about the fuel sources when defining the requirement for energy. To address these issues, it is worth summarizing recent findings about how nutrient and energy balance is achieved. According to the work of J.P. Flatt,52E. Jequiei3 and colleagues, and others: 1) dietary carbohydrate and fat have unequal effects on energy substrate metabolism and body energy balance; 2) the conversion of carbohydrate to fat is not an important pathway of carbohydrate dis458

posa154v55 in the person who is close to body energy balance or when glycogen stores are not saturated;563) dietary carbohydrate promotes carbohydrate oxidation56 and reduces lipid oxidation, whereas dietary fat does not enhance fat oxidation5’ or influence carbohydrate o ~ i d a t i o n 4) ; ~ imbal~ ances between intake and oxidation are more likely to occur for fat than for carbohydrate, and it follows that carbohydrate balance is under more strict metabolic control than is body fat balance.59Thus, we may conclude that: 1) carbohydrate and fat balances are regulated differently; 2) appreciable glycogen storage takes place before there is significant de novo lipogenesis from dietary and 3) adjustment of fat oxidation to altered dietary fat intake occurs eventually, but only after significant expansion of adipose tissue, which tends to increase blood fatty-acid concentrations and, hence, promote fat oxidation.60In contrast, when fat is provided as an intravenous infusion of lipid/ heparin, there is a prompt increase in fat oxidation and a reduction in insulin-stimulated carbohydrate oxidation.6’However, this situation is nutritionally and metabolically different from the more usual dietary situation that concerns us here. Thus, today it is no longer sufficient to assess only the balance between total energy intake and expenditure when defining human energy requirements. A quantitatively important metabolic component of the energy balance equation needs to be recognized, and the energy requirements of younger and older persons should be defined with due consideration of the concept of “nutrient balance” and the macronutrient composition of the diet .62 It follows from this summary of the metabolic aspects of carbohydrate and lipid utilization in relation to energy expenditure that a voluntary restriction of fat might well be desirable simply from an energy-balance perspective, not to mention the associated risks of cardio- and cerebrovascular disease. Hence, in determining energy requirements and in making recommendations about energy intakes in the elderly, one must give appropriate consideration to the source of the energy intake as well as to total energy expenditure. There is not as yet a broad consensus on what might be the “ideal” or “appropriate” mixture of net energy from carbohydrate and lipid sources. Perhaps the goals set forth in the 1990 WHO Report on Diet, Nutrition, and Prevention of Chronic Diseases63could serve, for now, as suitable guidelines for recommending fuel intakes to maintain energy balance and body composition. This expansion of our understanding of energy substrate metabolism helps to refine our knowledge about human nutrient and energy requirements. Nutrition Reviews, Vol. 50, No. 12

Protein and Amino Acid Requirements

The need for dietary protein arises largely because the turnover of tissue and organ proteins is accompanied by an inefficient recapture of their constituent amino acids, which are then lost from the body via oxidative metabolism. This leads to an elimination of their nitrogen moiety, mainly as urinary urea, and of the carbon skeletons of the nutritionally indispensable (essential) and dispensable (nonessential) amino acids, largely as expired carbon dioxide. Thus, the need for dietary protein has two components-a requirement for indispensable amino acids and a requirement for “nonspecific” nitrogen, used for the synthesis of the dispensable amino acids and other physiologically important nitrogen-containing compounds. The possible agerelated changes in each of these factors have been reviewed e l ~ e w h e r e . There ~ . ~ ~ are changes in the quantitative and qualitative aspects of body protein metabolism during the advancing adult years, but the nutritional implications of these changes have not been explored sufficiently. Thus, the determination of protein and amino acid requirements in the elderly is based on the same approach and principles that have been used to establish requirements in young adults. The FAO/WHO/UNU Expert Consultation3 has defined the protein requirement as “the lowest level of dietary protein intake that will balance the losses of nitrogen from the body in persons maintaining energy balance at modest levels of physical activity. In children and pregnant or lactating women, the protein requirement is taken to include the needs associated with the deposition of tissues or the secretion of milk at rates consistent with good health.” It would be useful, therefore, to discuss the rec-

ommendations made in the 1985 FAO/WHO/UNU3 report with regard to the current understanding of the protein and amino acid needs in the elderly. The first point is that the estimates of the physiological needs for good-quality dietary protein in adults are based on relatively short-term metabolic nitrogen (N) balance studies, with subjects receiving dietary proteins of high nutritional value and digestibility. The setting of “safe protein intakes” is then achieved by considering the variation in requirements among apparently similar persons within a population group and adding a correction for the digestibility of proteins in mixed diets. The safe protein intake has been set for adults at approximately 0.8 g/kg body weight per day.’.’ This level applies to healthy people, and in earlier reviews, we have surveyed how these needs are increased, and to what approximate extent, in elderly subjects who are not healthy .66 A second point worth making here is that the quantitative values of the requirements for the nutritionally indispensable (essential) amino acids in the elderly are uncertain, and the published literat ~ r eis ~highly , ~ inadequate ~ and mainly contradictory. Hence, using an approach that I have used for predicting the physiological needs for indispensable amino acids in healthy young adults,% it would appear that these needs in healthy elderly subjects (Table 7) are similar to those in the young. However, they are much higher than the currently proposed FAO/WHO/UNU3 estimates for maintenance of protein nutritional status in adult subjects. The approach followed herein to arrive at a tentative set of figures for amino acid requirements in elderly subjects has been criticized by Millward and Rivers.69 But it is my view that the approach used, given the absence of sufficient direct experimental

Table 7. Computed Oxidative Losses (COL) of Amino Acids and Intakes to Balance Those in Young Adult and Elderly Subjects and a Comparison with FAO/WHO/UNU (1985) Requirements Young Adult Amino Acid

COL

Elderly” Intake for Balance

COL

Intake for Balance

Adults FAO/WHO/UNU (1985)

mg kg-lday-’ 16 23 16 23 (17)b 10 Isoleucine Leucine 27 39 27 39 (28) 14 30 42 Lysine 30 42 (30) 12 SAA 13 16 13 16 (12) 13 21 39 AAA 27 39 (28) 13 15 21 Threonine 15 21 (15) 7 Tryptophan 4 6 4 6 (4) 3.5 17 24 Valine 17 24 (17) 10 ” Based on obligatory N losses reported by Uauy et aL6’ and 8 mg N kg-’day-’ for miscellaneous: total = 54 mg N kg - ‘day - . Figures in parentheses are those based on total N losses of 39 mg N kg-’day-’ as reported by Zanni et a1.68



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data and/or major evidence to the contrary, is reasonable for the present and is useful for planning and evaluating dietary adequacy. Nevertheless, there is an urgent need to confirm these predictions through direct studies in elderly subjects, since their validation is fundamental for a satisfactory understanding of the metabolic basis of protein requirements. The current state of knowledge about the protein and amino acid requirements in the elderly might be summarized as follows: 1) previous methods and experimental designs used to estimate the requirements for total nitrogen (protein) and indispensable amino acids are generally limited in scope, sensitivity, and/or validity; 2) nitrogen and amino acid requirements apparently do not decline, per unit of body weight, with aging, whereas daily energy needs are usually diminished; 3) it follows that an adequate diet for the elderly, therefore, should be somewhat higher in protein relative to energy intake than are diets for younger adults. We64,65 have proposed that about 12-14% of the energy intake should be as food proteins of the quality typical of an adequate, varied US diet; 4) higher protein intakes are required for tissue maintenance and repletion in the elderly who are in poor health. Guidelines for desirable levels of protein intake for various disease states have been suggested elsewhere.65 Summary and Conclusions

Quantitatively, the macronutrient needs in the elderly remain poorly defined. Given the importance of nutritional status as a determinant of function and well-being, this unsatisfactory situation should be challenged through significant investment of research effort and resources. Estimations of the energy requirements for the healthy elderly are based on the same principles used for young adults. Future research should focus on actual levels of energy expenditure, on the metabolic responses to altered energy intakes, and on the significance of different energy sources in maintaining body composition and function. Only with such additional data will we be able to state with some degree of assurance what level and sources of dietary energy are needed by, or should be recommended for, specific populations of elderly subjects. With respect to the protein and amino acid requirements in elderly subjects, new and improved methods are needed for assessing dietary protein and amino acid adequacy. Furthermore, the metabolic basis and the significance in host nitrogen economy and energy balance of the loss of muscle mass deserve exploration, and the requirements for specific indispensable amino acids need quantifica-

460

tion. The metabolic regulation and the nutritional significance of the “conditionally indispensable” amino acid^^',^' represent important areas for research in the area of aging and human protein nutrition. Finally, investigations are needed to assess the consequences of “stress” (physical, infection, psychological) on energy and protein metabolism and nutrition in older subjects. Acknowledgment. The author’s unpublished studies were supported by NIH grant AG 07388. I thank Dr. Susan Roberts for her valuable assistance in the design, conduct, and interpretation of these studies. 1. National Research Council. Recommended dietary allowances, 10th ed. Washington, DC: National Academy Press, 1989 2. Department of Health. Report on Health and Social Subjects. No. 41. Dietary reference values for food energy and nutrients for the United Kingdom. London: HMSO, 1991 3. FAOIWHOIUNU. Energy and protein requirements. Report of a Joint FAO/WHO/UNU Expert Consultation. Tech Rept Ser No. 74. Geneva: World Health Organization, 1985 4. FAO/WHO. Energy and protein requirements. Report of a Joint FAO/WHO Ad Hoc Expert Committee. Tech Rept Ser No. 522. Geneva: World Health Organization, 1973 5. Poehlman ET, Horton ES. Regulation of energy expenditure in aging humans. Ann Rev Nutr 1990; 10:255-75 6. Shock NW, Watkin DM, Tiengst MD, et al. Age differences in the water content of the body as related to basal oxygen consumption in males. J Gerontol 196318:1-8 7. Keys A, Taylor HL, Grande F. Basal metabolism and age in adult man. Metabolism 1973;22:57%87 8. Calloway DH, Zanni E. Energy requirements and energy expenditure of elderly men. Am J Clin Nutr 1980;33:2088-92 9. Poehlman ET, McAuliffe TL, VanHouten DR, Danforth E, Jr. Influence of age and endurance training on metabolic rate and hormones in healthy men. Am J Physiol 1990;259:E66-72 10. Fukagawa NK, Bandini LG, Young JB. Effect of age on body composition and resting metabolic rate. Am J Physiol 1990;259:E233-8 11. Vaughan L, Zurlo F, Ravussin E. Aging and energy expenditure. Am J Clin Nutr 1991;53:821-5 12. Forbes GB, Reina JC. Adult lean body mass decline with age: some longitudinal observations. Metabolism 1970;19:653-63 13. Cohn SH, Vartsky D, Yasumura S, et al. Compartmental body composition based on total body nitrogen, potassium and calcium. Am J Physiol 1980;239:E524-30 14. Flynn MA, Nolph GB, Baker AS, Martin WM, Krause G. Total body potassium in aging humans: a longitudinal study. Am J Clin Nutr 1989;50:713-7 15. Zurlo F, Larson K, Bogardus C, Ravussin E. Skel-

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eta1 muscle metabolism is a major determinant of resting energy expenditure. J Clin Invest 1990;86: 1423-7 16. Tzankoff SP, Norris AH. Effect of muscle mass decrease on age-related BMR changes. J Appl Physiol 1977;43:1001-6 17. Tzankoff SP, Norris AH. Longitudinal changes in basal metabolism in man. J Appl Physiol 1978;45: 536-9 18. Jequier E, Schutz Y. Energy expenditure in obesity and diabetes. Diabetes/Metabolism Revs 1988;4:583-93 19. Young JB, Rowe JW, Pallotta JA, Sparrow D, Londsberg L. Enhanced plasma norepinephrine response to upright pasture and oral glucose administration in elderly human subjects. Metabolism 1980;29:532-9 20. Heinsimer JA, Lefkowitz RJ. The impact of aging on adrenergic receptors; clinical and biological aspects. J Am Geriatr SOC1985;33:184-8 21. Veith RC, Featherstone JA, Linarea OA, Halter JB. Age differences in plasma norepinephrine kinetics in humans. J Gerontol 1986;41:319-24 22. Schwartz RS, Jaeger LF, Veith RC. The importance of body composition to the increase in plasma norepinephrine appearance rate in elderly men. J Gerontol 1987;42:546-51 23. Poehlman ET, McAuliffe T, Danforth E, Jr. Effects of age and level of physical activity on plasma norepinephrine kinetics. Am J Physiol 1990;258: E256-62 24. Golay A, Schutz Y, Broquet C, Moeri R, Felber JP, Jequier E. Decreased thermogenic response to an oral glucose load in older subjects. J Am Geriatr SOC1983;31:144-8 25. Schwartz RS, Jaeger LF, Veith RC. The thermic effect of feeding in older men: the importance of the sympathetic nervous system. Metabolism 1990;39:733-7 26. Bloesch D, Breitenstein E, Jequier E, Felber JP. Thermogenic response to an oral glucose lead in man: comparison between young and elderly subjects. J Am Coll Nutr 1988;7:471-83 27. Morgan JB, York AD. Thermic effect of feeding in relation to energy balance in elderly men. Ann Nutr Metab 1983;27:71-7 28. Tuttle WW, Horvath SM, Pcesson LF, Daum K. Specific dynamic action of protein in men past 60 years of age. J Appl Physiol 1953;5:631-4 29. Fukagawa NK, Bandini LG, Lim P-H, Roingeard F, Lee MA, Young JB. Protein-induced changes in energy expenditure in young and old individuals. Am J Physiol 1991;260:E345-52 30. Tai MM, Castillo P, Pi-Sunyer FX. Meal size and frequency: effect on the thermic effect of food. Am J Clin Nutr 1991;54:783-7 31. Ravussin E, Schutz Y, Acheson KJ, Dusmet M, Bourquin L, Jequier E. Short-term, mixed-diet overfeeding man: no evidence for “lukuskonsumption.” Am J Physiol 1985;249:E47&7 32. Roberts SB, Young VR, Fuss P, et al. Energy expenditure and subsequent nutrient intakes in Nutrition Reviews, Vol. 50, No. 12

overfed young men. Am J Physiol 1990;259: R461-9 33. Forbes GB, Brown MR, Welle SL, Lipinski BA. Deliberate overfeeding in women and men: energy cost and composition of the weight gain. Br J Nutr 1986;56:1-9 34. Bouchard C, Tremblay A, Despres JP, et al. The response to long-term overfeeding in identical twins. N Engl J Med 1990;322:1477-82 35. Bandini LG, Schoeller DA, Edwards J, Young VR, Oh SH, Dietz WH. Energy expenditure during carbohydrate overfeeding in obese and nonobese adolescents. Am J Physiol 1989;256:E357-67 36. Waterlow JC. Nutritional adaptation in man: general introduction and concepts. Am J Clin Nutr 1990;51:25%63 37. Schoeller DA. How accurate is self-reported dietary energy intake? Nutr Rev 1990;48:373-9 38. Livingstone MBE, Prentice AM, Strain JJ, et al. Accuracy of weighed dietary records in studies of diet and health. Br Med J 1990;300:708-12 39. Mertz W, Fsui JC, Judd JT. What are people really eating? The relation between energy intake derived from estimated diet records and intake determined to maintain body weight. Am J Clin Nutr 1991;54:291-5 40. Roberts SB, Heyman MB, Evans WJ, Fuss P, Tsay R, Young VR. Dietary energy requirements of young adult men, determined using the doublylabeled water method. Am J Clin Nutr 1991;54: 499-505 41. Roberts SB, Young VR, Fuss P. What are the dietary energy needs of adults? 1992 (submitted) 42. Schoeller DA. Measurement of energy expenditure in free-living humans by using doubly labeled water. J Nutr 1988;118:127689 43. Prentice AM (ed). The doubly-labelled water method for measuring energy expenditure. Technical recommendations for use in humans. National and health-related environmental studies, No. 4. Vienna: International Atomic Energy Agency, 1990 44. Davidson MB. The effect of aging on carbohydrate metabolism: a review of the English literature and a practical approach to the diagnosis of diabetes mellitus in the elderly. Metabolism 1979;29:688705 45. Robert JJ, Cummins JC, Wolfe RR, et al. Quantitative aspects of glucose production and metabolism in healthy elderly subjects. Diabetes 1982;32: 203-1 1 46. Broughton DL, James OVW, Alberti KGMM, Taylor R. Peripheral and hepatic insulin sensitivity in elderly healthy subjects. Eur J Clin Invest 1991;21: 13-21 47. Betrand HA, Anderson WR, Masoro EJ, Yu BP. Action in food restriction on age-related changes in adipoctye lipolysis. J Gerontol 1987;42:666-73 48. Twersky J, Hoffman BB, Reaven GM. Ageassociated differences i n beta adrenergicstimulated lipolysis in adipocytes from Sprague461

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Nutrition Reviews, Vol. 50, No. 12

Macronutrient needs in the elderly.

December 1992: 454-462 Macronutrient Needs in the Elderly Vernon R. Young, Ph.D, D.Sc. introduction This short review will highlight some of the si...
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