Loss of abdominal fat and metabolic response to exercise training in obese women.

Loss of abdominal fat and metabolic to exercise training in obese women

response

JEAN-PIERRE DESPRfiS, MARIE-CHRISTINE POULIOT, SITAL MOORJANI, ANDRfi NADEAU, ANGELO TREMBLAY, PAUL J. LUPIEN, GERMAIN THfiRIAULT, AND CLAUDE BOUCHARD Physical Activity Sciences Laboratory, Lava1 University, Lipid Research Center and Diabetes Research Unit, Lava1 University Medical Research Center, Sainte-Foy, Quebec GlK 7P4, Canada

diabetes and atherosclerosis. During the 1980s numerous studies proved that a high accumulation of abdominal LUPIEN, GERMAIN THI~RIAULT, AND CLAUDE BOUCHARD. LOSS fat was associated with metabolic complications such as of abdominalfat and metabolic response to exercise training in glucose intolerance, hyperinsulinemia, diabetes, and hyobese women. Am. J. Physiol. 261 (Endocrinol. Metab. 24): pertension and with changes in plasma triglyceride (TG) E159-E167, 1991.-Numerous studies have shown that a high and high-density lipoprotein (HDL) -cholesterol (Chol) accumulation of abdominal fat is associated with metabolic concentrations (for reviews, see 2,8,20). These metabolic complications and with an increased risk of coronary heart changes may contribute to the cardiovascular disease disease. The present study examined the effects of changes in risk that is associated with an altered distribution of body fatness and in the level of abdominal fat on metabolic body fat. However, most previous studies have used variables in a sample of 13 obese premenopausal women, aged 38.8 k 5.3 (SD) yr. Women exercised for 90 min at -55% of subcutaneous skinfold measurements and/or the waistmaximal aerobic power (VO, mBX) four to five times a week for to-hip circumference ratio to estimate the proportion of a period of 14 mo. The training program induced a significant abdominal fat. Because it has been suggested that deep increase in VO 2 max and a mean reduction in body fat mass of abdominal fat accumulation could be important in the 4.6 kg (P < O.Ol),with no change in fat-free mass. Measurement metabolic complications related to an excess amount of of adipose tissue areas by computed tomography indicated a abdominal fat (15, 37), we have used computed tomoggreater loss of abdominal fat compared with midthigh adipose raphy (CT) to measure body fat distribution and the tissue (P < 0.05). The training program also produced signifiamount of deep and subcutaneous abdominal fat (8). We cant reductions in the insulinogenic index measured during an have observed that a high accumulation of deep abdomoral glucose tolerance test and in plasma cholesterol (Chol), inal fat was associated with disturbances in glucoselow-density lipoprotein (LDL)-Chol, and apolipoprotein (apo) insulin homeostasis and in plasma lipid transport, sugB levels (P < 0.05).Training also significantly increased plasma high-density lipoprotein (HDL)-apo A-I and HDL2-Chol levels gesting an increased risk of diabetes and CHD in indiand decreased plasma HDL: 1.006 g/ml) with heparin and MnC12 (4). The Chol and TG content of the infranatant fraction was measured before and after the precipitation step. Apolipoprotein (apo) B concentration was measured in plasma, and the infranatant (LDL-apo B) was measured by the rocket immunoelectrophoretic method of Laurel1 (24) as previously described (28). Apo A-I concentration was also measured in the infranatant fraction. The lyophilized serum standards for apo measurements were prepared in our laboratory and were calibrated with reference standards obtained from the Centers for Disease Control, Atlanta, GA. The concentrations of LDL-Chol, LDL-TG, and VLDL-apo B were obtained by difference. The Chol content of HDL, and

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EXERCISE

HDL:,

subfractions

prepared

TRAINING

by precipitation

AND

METABOLISM

method

(16) was also determined.

Plasma postheparin lipoprotein lipase (LPL) and hepatic triglyceride lipase , (HTGL) activities were measured in plasma obtained from subjects who had fasted for 12 h, 10 and 20 min after an intravenous injection of heparin (10 IU/kg body wt). Selective assays for LPL and HTGL activities were performed by a modification of the method of Nilsson-Ehle and Ekman (31). These assays yield results that are in good agreement with those obtained with the selective inhibition of HTGL with antibodies (30). Plasma was separated by low-speed centrifugation at 4”C, and a O.&ml aliquot was frozen and lyophilized overnight. Acetone-ether powders were then prepared from these samples, dried under nitrogen, and stored at -20°C for later assays. The acetone-ether powders were dissolved in 2 ml of 0.9% NaCl and were used as an enzyme source for the measurements of both LPL and HTGL activities using two different substrates and selective assay conditions. Statistical analyses. The effect of exercise training was assessed by a one-way analysis of variance for repeated measurements (46). Pearson’s product-moment coefficients were also calculated to study the associations between variables. RESULTS

Table I shows that the aerobic exercise training program produced a significant increase in maximal aerobic power (P < 0.01) and a significant reduction in body weight (P < 0.05). Body composition analysis revealed that the reduction in body weight was entirely explained by the loss of body fat, as fat-free mass showed no significant change after training. As the net energy cost of each exercise session ranged from 300 to 550 kcal, the body energy loss [27,600 kcal, if we assume an energy equivalent of 6,000 kcal/kg of adipose tissue (lo)] was less than expected from the total energy expenditure produced by the exercise training program. Table 2 presents the effect of aerobic training on the regional distribution of body fat measured by CT. The total adipose tissue area at the abdominal level was significantly reduced after training (P < 0.01). Such reduction was entirely explained by the decrease in the area of subcutaneous abdominal fat, as no change was observed in the deep abdominal fat area after training. The midthigh fat area was also significantly reduced after training. As most femoral adipose tissue is located TABLE 1. Effects of 14-mo aerobic exercise training program on maximal aerobic power and body composition in obesewomen Variable vo 2 ITI~IX~l/min

Weight, kg BMI, kg/m’ %Body fat Fat mass, kg Fat-free mass, kg

Before

2.19kO.26 9O.O-el1.8 34.5k4.3 47.os.5

42.6t9.4 47.4t5.1

Values are means k SD; n = 13 women. power; BMI, body mass index. * P < 0.01, t

After

2.52t0.35* 86.3k9.6t 33.lt3.6t 43.7t4.8* 38.0t7.3* 48.3k4.1

VO, max, maximal

P < 0.05.

aerobic

IN

OBESE

El61

WOMEN

TABLE 2. Effect of 14-mo aerobic exercise training program on adipose tissue areas measured by computed tomography in obesewomen Area,

cm’

Trunk (T8-T9) Total Subcutaneous Deep Abdomen ( L4-Ls) Total Subcutaneous Deep Midthigh Total Subcutaneous Deep Partial adipose tissue volume (liters) Abdo subclmidthigh subc

Before

After

337.3t102.4

305.3t102.9

267.0k77.8 70.3t32.8

239.6t82.5

671.2U49.8

607.8&146.3*

546.5k128.2

486.5t123.3* 121.3245.5

124.7k48.6 487.7t84.8 473.2k87.2 14.6t7.0 27.8t5.6

65.8t31.9

450.1&80.9* 437.5&82.4* 12.6t4.7 25.1t5.5*

1.17kO.23

1.12t0.23t

Values are means & SD; n = 13 women. ratio of abdominal subcutaneous to midthigh

Abdo subc/midthigh subcutaneous. *

subc,

P < 0.01,

t P c 0.05.

subcutaneously, such reduction was mainly caused by a decrease in the subcutaneous fat area. The significant reduction in the ratio of abdominal to femoral subcutaneous adipose tissue areas observed after training indicated a greater mobilization of abdominal than femoral fat. The partial adipose tissue volume calculated from the T8-T9 scan to the midthigh scan also showed a significant reduction after training. The percent reduction in partial adipose tissue volume (-10%) was concordant with the decrease in total body fat mass (-ll%), and changes of both variables were significantly correlated (r = 0.70, P < 0.01). These results support the notion that there was no substantial change in the density of fat-free mass in response to the exercise training program. As there was no significant change in the amount of visceral fat after training, we investigated the potential relation of changes in the level of deep abdominal fat to the magnitude of total body fat loss. Results presented in Fig. 1 indicate that the greater the loss of total body fat with training, the greater was the reduction in the amount of deep abdominal fat. The effects of the aerobic exercise training program on glucose tolerance and on plasma insulin and C-peptide levels are presented in Table 3. Oral glucose tolerance was not significantly altered with training, whereas an almost significant (P c 0.06) trend for a reduction in the insulin area was noted. The insulinogenic index (ratio of insulin area/glucose area) was significantly reduced after training. Fasting C-peptide levels were significantly reduced after training, whereas the C-peptide area was not modified by the exercise program. Plasma HDLP-Chol levels were significantly increased after training (Fig. 2), whereas the amount of Chol transported by the HDL3 subfraction was significantly reduced. Such an increase in HDLZ-Chol, combined with the reduction in HDLS-Chol, accounted for the lack of significant change in plasma HDL-Chol level. Training also produced a reduction in plasma Chol and LDL-Chol levels (Table 4). Table 4 also presents the effects of aerobic training on plasma apo levels and


EXERCISE

TRAINING

AND

METABOLISM

IN

OBESE

WOMEN

60 r = 0.70

0.0

HDL,

HDL I

I

I

I

I

I

-15

-10

-5

0

5

10

I

CHANGES FIG. 1. Relationship and loss of total body premenopausal women.

IN FAT MASS

(kg)

between changes in deep abdominal fat area fat induced by aerobic exercise training in 13

TABLE 3. Effects of 14-mo aerobic exercise training program on carbohydrate metabolism in obesewomen Before

Variable

Fasting values Glucose, mg/dl Insulin, PI-J/ml C-peptide, rig/ml Glucose tolerance test Glucose area, (mg dl-’ min-‘) l

After

93.9t8.6 14.3t7.3 3.3t0.9

90.5k7.1 11.5t4.9 3.0t0.7*

22.8k4.7

22.1k3.7

15.7k6.4

12.6G.l

x lo-:’

Insulin ml-‘.

area, (& min-‘)

t

x 1o-:1

C-peptide area, (ng- ml-’ min-‘)

1.7kO.4

1.6t0.4

0.72kO.34

0.59*0.25*

l

x 1o-:3

Insulin/glucose areas Values

are means

k SD; n = 12 women.

* P < 0.05, t

FIG. 2. Effect of 14-mo aerobic exercise training program on cholesterol (Chol) content of plasma high-density lipoproteins (HDL), as well as on plasma HDL*-Chol and HDLS-Chol levels in obese women. Open bars, before training; hatched bars, after training. * P < 0.05; n = 12 women.

TABLE 4. Effects of 14-mo aerobic exercise training program on plasma lipid, lipoprotein, and apoprotein levels, as well as on plasma lipoprotein ratios in obesewomen Variables

l

P < 0.06.

lipoprotein ratios commonly used in the estimation of the risk of CHD. Whereas plasma apo B levels were significantly reduced, plasma HDL-apo A-I levels were significantly increased after training. A marked increase in the HDL-apo A-I/LDL-apo B ratio was also observed. Due to the lack of change in plasma HDL-Chol levels, the HDL-Chol/LDL-Chol ratio was not significantly increased by aerobic training. However, due to the reciprocal changes in plasma HDL2-Chol and HDLS-Chol levels, a substantial increase in the HDLZ-Chol/HDLsChol ratio was noted. Figure 3 shows the effects of the endurance training program on plasma postheparin LPL and HTGL activities. Whereas plasma postheparin LPL activity was not significantly increased with training, a marked reduction

HDL,

TG, mM Chol, mM VLDL-Chol, mM LDL-Chol, mM Apo B, mg/dl HDL-apo A-I, mg/dl HDL-Chol/LDL-Chol HDLz-Chol/HDLs-Chol HDL-apo A-I/LDL-apo

Before

B

1.7OkO.60 5.67t0.50 0.54kO.21 4.06t0.47 108.2t17.4 109.3k13.5 0.27t0.05 0.60&0.08 1.17k0.18

After

1.74t0.60 5.28t0.70* 0.57kO.23 3.67t0.59* 95.7&18.9* 123.3H6.4t 0.29kO.05 0.85kO.24 1.42*0.27t

t

Values are means k SD; n = 12 women. TG, triglyceride; Chol, cholesterol; VLDL, very low-density lipoprotein; LDL, low-density lipoprotein; apo B and A-I, apolipoprotein B and A-I; HDL, highdensity lipoprotein. * P < 0.05, t P < 0.01.

in plasma postheparin HTGL activity was noted. Individual changes in the activity of both enzymes were not, however, correlated with the magnitude of total or abdominal fat losses. Furthermore, no association was found between changes in plasma postheparin HTGL activity and changes in plasma HDL2-Chol or in the HDLz-Chol/HDL3-Chol ratio. Because this lack of relationship may have been caused by the simultaneous reciprocal changes in LPL and HTGL activities, we have examined the correlations between changes in the LPL/ HTGL ratio and changes in plasma lipoprotein levels. First, changes in body fat mass were negatively correlated with changes in the LPL/HTGL ratio (r = -0.65, P < 0.05) (Fig. 4A). Second, results shown in Fig. 4B indicate that changes in the LPL/HTGL ratio were positively correlated with changes in the HDL-Chol/LDL-Chol ratio (r = 0.75, P < 0.05). Therefore, women that showed the highest loss of body fat also showed the highest


EXERCISE

TRAINING

AND

METABOLISM

IN

OBESE

El63

WOMEN

r -0.65 p =< 0.05

c

6

w

0.2

BEFORE

AFTER

0.4

Changes

in

LPL/HTGL

0.6

0.8

ratio

n

.-s E

40

0’ 5

\ E >

!J f: 3 0

30

E t w

E

3 !J n I .-c

20

: 0, 6 5 CL

0.10

0.06

0.02

-0.02

-0.06

P

I

0.2

BEFORE

I

I

I

0.4

0.6

0.8

AFTER Changes

3. Effect of 14-mo aerobic exercise training program on plasma postheparin (PH) lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities. NS, not significant; * P < 0.005; n = 9 women.

in

LPL/HTGL

ratio

FIG.

activity of LPL as compared with HTGL and the highest HDL-Chol/LDL-Chol ratio after endurance training. Finally, Table 5 presents correlation coefficients for the associations between changes in total body fatness, regional fat depots, maximal aerobic power, and changes in the metabolic profile. Changes in maximal aerobic power produced by the training program were not correlated with changes in the metabolic variables. Changes in total body fat mass, as well as in subcutaneous upper trunk, abdominal, and midthigh fat areas were all significantly correlated with changes in plasma Chol and LDLChol levels. Changes in glucose tolerance induced by training were significantly correlated with changes in body fat mass and in the level of deep abdominal fat but not with changes in the level of subcutaneous abdominal fat nor with levels of upper trunk or femoral fat. The response of plasma TG levels to training was significantly correlated with changes in the level of deep abdominal fat but not with changes in total body fat or in any other fat depot. Finally, the response of the HDLChol/LDL-Chol ratio was significantly correlated with the magnitude of body fat loss and with the reduction in the amount of deep abdominal fat. DISCUSSION

The present aerobic exercise training program produced a significant increase in maximal aerobic power and a significant decrease in body weight. The reduction

FIG. 4. Correlations between changes in LPL/HTGL ratio changes in body fat mass and changes in the HDL-Chol/LDL-Chol ratio; n = 9 women.

and

in body weight was entirely accounted for by a decrease in body fat mass, as no significant reduction in fat-free mass was noted after training. Furthermore, the concordance between changes in hydrostatic weighing-derived body fat mass (reduction of 10.8%) and in CTmeasured partial adipose tissue volume (reduction of 10.5%) suggested that no substantial change in the density of fat-free mass was produced by the present exercise program. This conclusion should, however, be limited to the present sample of obese premenopausal women and to the present exercise protocol, and further studies on the validation of body density as a mean to assess changes in body composition are needed. The preservation of fat-free mass during exercise training-related weight loss has been, however, frequently reported (7, 25, 41). As previously mentioned, the loss of body energy stored as fat was obviously less than what could be expected from the estimated net energy cost of each exercise session (from -300 to 550 kcal). We have previously reported resistance to fat loss in women compared with men (7, 41). This resistance of women to fat loss could be explained by an increase in energy intake, by a reduction in energy expenditure during nonexercise periods and to a higher proportion of peripheral less lipolytically responsive gluteofemoral adipose tissue in women than in men (10). The present study confirmed that, in freely eating obese women, the net energy ex-


El64

EXERCISE

TRAINING

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METABOLISM

IN

OBESE

WOMEN

5. Correlation coefficients between changes in maximal aerobic power, body fat mass, CT-derived measures of subcutaneous abdominal and femoral adipose tissue areas, deep abdominal fat area, and metabolic responses induced by 14-mo aerobic exercise training program in premenopausal obesewomen

TABLE

Correlation Abdominal VO

Glucose area Insulin area TG Chol LDL-Chol HDL2-Chol HDLyChol HDL-Chol/LDL-Chol

2 mnx

-0.17

-0.18 0.07 -0.36 -0.38 0.32 -0.32 0.12

Coefficients

fat

Trunk

fat

Midthigh

Fat mass

0.64* 0.54 0.35 0.67* 0.61* -0.29 -0.22 -0.60*

Subc

Deep

Subc

Deep

Subc

Deep

0.17 0.41 0.27 0.71* 0.63* -0.37 -0.13 -0.56

0.67” 0.49 0.67* 0.67* 0.53 -0.54 -0.30 -0.66*

0.12 0.30

-0.10 0.20 0.32 0.30 0.24 -0.44 -0.27 -0.45

0.48 0.58 0.34 0.77t 0.65* -0.34 -0.06 -0.53

0.41 0.20 0.37 0.65* 0.56 -0.47 -0.03 -0.47

penditure above basal sedentary energy expenditure produced by prolonged aerobic exercise cannot be used to predict fat loss during an exercise training program. It has been well documented that abdominal adipose cells show a higher lipolytic response to catecholamines than adipocytes obtained from the gluteal and femoral regions (21, 36). For that reason, it had been previously suggested that the fat mobilization during exercise training-induced weight loss should be greater in the abdominal than in the gluteofemoral region (40). To address this issue, we have studied the regional distribution of body fat using CT, a technique that allows the measurement of adipose tissue areas at various sites of the body. Whereas a nonsignificant trend for a reduction in trunk fat was observed, the adipose tissue area measured at the abdominal level was significantly reduced at the end of the training program. This reduction was due to a decrease in the subcutaneous abdominal fat compartment, as the amount of deep abdominal fat was not modified by training. Although the reduction of subcutaneous midthigh fat was also significant after training, the significant reduction in the ratio of subcutaneous abdominal to femoral fat area suggested a greater mobilization of abdominal than femoral subcutaneous fat in response to exercise training in these obese women. These results on the preferential mobilization of abdominal fat during exercise training-induced weight loss confirmed our previous results in nonobese men and women in which changes in subcutaneous fat accumulation were studied using skinfold measurements (10, 40). In the present study, however, no preferential loss of deep abdominal fat was observed. This result could, at first, appear as surprising since the omental fat depot has been documented to have a lively lipolysis that is resistant to the antilipolytic action of insulin (3). Such condition should have, at least theoretically, favored the preferential mobilization of deep abdominal fat. However, substantial individual variation in the response of the deep abdominal fat depot was noted. Four out of thirteen women even showed increases in the level of deep abdominal fat after training. The magnitude of reduction in the deep abdominal fat area was significantly correlated with the loss of total body fat mass (r = 0.70, P < O.Ol), indicating that deep abdominal fat was, indeed, mobilized when fat loss was substantial. We have also recently shown that the

0.11

0.68* 0.67* -0.24 -0.09 -0.46

level of total body fat is weakly correlated with the amount of deep abdominal fat in premenopausal women (14), indicating that the subcutaneous and deep adipose tissue compartments may vary independently from each other. Finally, other variables that should be considered when discussing the effect of aerobic exercise traininginduced weight loss on the level of deep abdominal fat include gender, age, the level of obesity, and the initial level of deep abdominal fat (40). Clearly, additional studies in young and old subjects of both sexes, differing in their initial body fatness and fat distribution characteristics, are needed. The major aim of the present study was to verify whether the preferential mobilization of abdominal fat associated with aerobic exercise training could have beneficial effects on the metabolic profile of obese women. We had previously reported, in a larger sample of premenopausal obese women with physical characteristics comparable to the women of the present study, that the level of deep abdominal fat was the best correlate of glucose tolerance and of lipoprotein ratios used in the estimation of the risk of CHD (8). Among obese women, these associations were fully independent from total body fatness. We therefore wanted to study the potential effects of exercise training-related changes in fat distribution on the metabolic profile of obese women. The training program produced many potentially beneficial metabolic effects. Indeed, the insulin area measured during an oral glucose tolerance test showed a trend (P < 0.06) for a reduction after training, whereas the insulinogenic index (ratio of insulin/glucose areas) was significantly reduced, suggesting an increased tissue insulin sensitivity. This reduction in the insulinogenic index was observed despite the lack of significant change in insulin secretion, as estimated by the response of C-peptide measured during the oral glucose tolerance test. This result may suggest, in concordance with our previous studies (42), that the first adaptation occurring in insulin metabolism during exercise training is an increased metabolic clearance of insulin, probably through an increased hepatic extraction of insulin, with insulin secretion taking a much longer exercise training period to show a significant reduction in the obese (42). Furthermore, although glucose tolerance was not significantly improved after training, women displayed individual var-


EXERCISE

TRAINING

AND

METABOLISM

iation in the response of glucose tolerance to training. Individual changes in glucose tolerance were positively correlated with changes in body fat mass and with changes in the level of deep abdominal fat. These results suggest that women who lost the largest amount of total body fat and of deep abdominal fat were those who showed the greatest improvements in glucose tolerance after training. Changes in glucose tolerance were not correlated with changes in mid-thigh fat nor with changes in the level of subcutaneous abdominal fat, indicating that the changes in the deep abdominal fat compartment were independently associated with the improvement of glucose tolerance. Further studies will be required to identify the mechanism(s) responsible for this dynamic association, but it has been suggested that the high lipolytic response of deep abdominal adipose cells to catecholamines, combined to their proximity to the liver through the portal circulation, could expose the liver to high free fatty acid concentrations, leading to a decreased hepatic extraction of insulin and to insulin resistance (2, 20). It appears reasonable to hypothesize that women who have shown reductions in their deep abdominal adipose mass may have improved their hepatic metabolism of glucose and insulin by reducing the exposure of the liver to high portal free fatty acid concentrations. Further research is, however, needed to identify the mechanism(s) responsible for the beneficial effects of a reduction in the amount of deep abdominal fat on plasma glucose and insulin homeostasis. The aerobic training program also produced significant changes in plasma lipoprotein levels, reflecting improvements in plasma lipid transport. As consistently reported in our previous studies (9, II), exercise training induced significant reductions in plasma Chol and in LDL-Chol levels. These changes in Chol and LDL-Chol were, however, equally correlated with changes in body fat mass and with alterations in subcutaneous upper trunk, abdominal, and midthigh fat areas. These results suggest that the response of total Chol and of LDL-Chol was more related to the loss of total body fat than to the regional mobilization of fat. Williams et al. (45) recently reported that exercise training-induced weight loss was associated with a reduction in the mass of small LDL that should contribute to reduce the risk of CHD in exercise-trained individuals. In addition, Wood et al. (47) have indicated that the weight loss associated with aerobic exercise training was an important correlate of training-induced changes in HDL-Chol levels and of changes in the concentrations of HDL subfractions. In the present study, a significant increase in plasma HDLZ-Chol and a decrease in plasma HDL3-Chol were observed. Such reciprocal changes in the Chol content of these two HDL subfractions explained the lack of change in plasma HDL-Chol levels. These results are concordant with the previous study of Nye et al. (32) and indicate that the lack of increase in plasma HDL levels that has been frequently reported in exercise training studies could be the consequence of opposite changes in the Chol content of HDL subfractions. Because the ratio of HDL2-Chol/ HDLij-Chol has been suggested as being useful in the estimation of the CHD risk (27), the marked increase in this ratio observed in the present study suggests that

IN

OBESE

WOMEN

El65

obese women clearly benefited from regular aerobic exercise. Changes of both subfractions were not, however, correlated with changes in body fatness or with changes in body fat distribution, suggesting that the response of these subfractions could be dependent on other mechanisms. The activities of LPL and of HTGL that can be measured in postheparin plasma have very significant effects on plasma lipid transport and are significant correlates of plasma HDL, and HDL3 concentrations (13, 39). Aerobic exercise training has been reported to increase plasma postheparin LPL activity and to decrease HTGL activity (for review, see Ref. 17). In the present study, the trend for an increase in plasma postheparin LPL activity was not significant, but postheparin HTGL activity displayed a marked reduction with training. These results are concordant with those of Stefanick et al. (38), who reported a significant decrease in postheparin HTGL activity after exercise training induced fat loss in obese men. As a high postheparin HTGL activity has been associated with low HDL-Chol (especially the HDLZ subfraction) (39), this effect of aerobic exercise training on plasma postheparin lipases could h ave contributed to the increase in the plasma HDLa-Chol/HDLs-Chol ratio that we observed in the present study. We have recently reported that obese women with high levels of deep abdominal fat have high HTGL activity and low HDL2-Chol levels (8). Results of the present study indicate that aerobic exercise training increased the proportion of HDL2-Chol in the plasma through a reduction in HTGL activity. No correlation was observed, however, between changes in plasma postheparin HTGL activity and changes&n plasma HDL2Chol or in the HDL2-Chol/HDL3-Chol ratio. This lack of relationship may be explained by the simultaneous reciprocal changes in LPL and HTGL activities. Indeed, for some subjects, a substantial decrease in HTGL activity was accompanied by little change in LPL activity, whereas in other women, a decrease in HTGL activity may have been observed along a marked increase in LPL activity. To control for such reciprocal changes, we have examined the correlations between changes in the LPL/ HTGL ratio and changes in plasma lipoprotein levels, and our results indicated that the greater the fat loss with training, the higher was the activity of LPL as compared with HTGL and the higher was the HDLChol/LDL-Chol ratio after endurance training. These results provide further evidence that the balance between plasma postheparin LPL and HTGL activities are related to the magnitude of exercise training-induced fat loss and that the relative response of these two enzymes are important determinants of the lipoprotein changes produced by endurance exercise training in obese women. In addition, changes in the commonly used HDL-Chol/ LDL-Chol ratio were proportionate to the magnitude of weight loss and to the amount of deep abdominal fat loss. However, obvious trends for association with changes in subcutaneous abdominal fat and in mid-thigh fat were noted. Therefore, we cannot conclude that changes in the HDL-Chol/LDL-Chol ratio were solely dependent upon the preferential mobilization of abdominal fat. It rather appears that the improvement in this ratio was proportionate to the magnitude of total body fat loss.


El66

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Overall, results of the present study support the notion that changes in total body fat and in the proportion of abdominal fat are both important correlates of exercise training-induced changes in carbohydrate and lipid metabolism. Further research will be needed to identify the mechanisms responsible for the dynamic associations between body fatness, body fat distribution, and metabolism in response to exercise training. Finally, as frequently reported in our previous exercise training studies (9, II), the metabolic changes produced by the exercise training program were not correlated with changes in maximal aerobic power. This lack of association is consistent with the notion that, although maximal aerobic power and glucose and lipid metabolism show significant adaptations to endurance training, cardiovascular fitness and “metabolic fitness” are improved at different rates and independently from each other by regular aerobic exercise (6). Therefore, the effects of aerobic exercise training on carbohydrate metabolism and on plasma lipid transport in obese women appear to be independent from training-related changes in cardiovascular fitness and are more dependent on metabolic processes related to the loss of total body fat and to the reduction in abdominal fat stores (6). We are grateful to the subjects for excellent collaboration and to the staff of the Physical Activity Sciences Laboratory, the Lipid Research Center, and the Diabetes Research Unit. Thanks are expressed to Judith Maheux, Benoit Lamarche, Jacinthe Hovington, Martine Marcotte, Henri Bessette, and Claude Leblanc for help in the collection and analysis of the data. The dedicated work of Nicole Roy, Yolande Montreuil, Marie Martin, Rachel Duchesne, Suzanne Roy, and JeanGuy Bertrand is also acknowledged. This research was supported by the Canadian Fitness and Lifestyle Research Institute, the Quebec Heart Foundation, the Natural Sciences and Engineering Research Council of Canada, and by the Fonds de la Recherche en Sante du Quebec (FRSQ). J.-P. Despres is an FRSQ research scholar, whereas M.-C. Pouliot received an FRSQ fellowship. Address for reprint requests: J.-P. Despres, Physical Sciences Laboratory, PEPS, Lava1 University, St. Foy, Quebec GlK 7P4, Canada. Received

17 September

1990; accepted

in final

form

27 March

1991.

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A home-based treadmill training reduced epicardial and abdominal fat in postmenopausal women with metabolic syndrome.

Comparable Effects of High-Intensity Interval Training and Prolonged Continuous Exercise Training on Abdominal Visceral Fat Reduction in Obese Young Women.

Loss of bone strength in response to exercise-induced weight loss in obese postmenopausal women: results from a pilot study.

Onset of exercise and diet program in obese women: metabolic and anorexigenic responses related to weight loss and physical capacities.

Effect of abdominal resistance exercise on abdominal subcutaneous fat of obese women: a randomized controlled trial using ultrasound imaging assessments.

Reactive Oxygen Species Response to Exercise Training and Weight Loss in Sedentary Overweight and Obese Female Adults.

Is body fat loss a determinant factor in the improvement of carbohydrate and lipid metabolism following aerobic exercise training in obese women?

Weight loss experiences of obese perimenopausal women with metabolic syndrome.

Running sprint interval training induces fat loss in women.

Effect of exercise on abdominal fat loss in men and women with and without type 2 diabetes.

Visceral fat accumulation in obese subjects: relation to energy expenditure and response to weight loss.

Resting metabolic rate, body-fat distribution, and visceral fat in obese women.

Effects of 12 weeks of combined exercise training on visfatin and metabolic syndrome factors in obese middle-aged women.

Abdominal fat cell lipolysis, body fat distribution, and metabolic variables in premenopausal women.

Response of oxidative stress and inflammatory biomarkers to a 12-week aerobic exercise training in women with metabolic syndrome.

Exercise training improves fat distribution patterns in 60- to 70-year-old men and women.

Examination of the Consistency in Affective Response to Acute Exercise in Overweight and Obese Women.

Zinc-α2-glycoprotein expression in adipose tissue of obese postmenopausal women before and after weight loss and exercise + weight loss.

Exercise Training and Weight Gain in Obese Pregnant Women: A Randomized Controlled Trial (ETIP Trial).

Impaired plasma catecholamine response to submaximal treadmill exercise in obese women.

The adaptive metabolic response to exercise-induced weight loss influences both energy expenditure and energy intake.

Metabolic responses to dietary fatty acids in obese women.

Modelling broilers' abdominal fat in response to dietary treatments.