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Biomedical subjects

C Bouchard

Publications and source records attributed to C Bouchard.

At least 487 records · Page 27Linked to original sources
PubMed1990

Long-term exercise training with constant energy intake. 1: Effect on body composition and selected metabolic variables.

The effects of long-term negative energy balance generated by exercise while maintaining a constant energy intake were studied in five healthy young males (25 +/- 3 years; mean +/- s.d.). After 2 weeks of monitoring to determine habitual energy intake, they were subjected to a 100-day experimental period during which they exercised on a cycle ergometer, 6 days a week, twice a day at 55 per cent of VO2 max. The daily energy deficit was 4.2 MJ for a total of 353 MJ for the duration of the treatment. Body weight decreased from 86.7 to 78.7 kg (P less than 0.001). More than 80 per cent of the weight loss was accounted for by the reductions in fat mass. Fat-free mass did not change significantly. The data suggest that subcutaneous fat was lost about evenly from the trunk and from the limbs as estimated from skinfolds. Cardiorespiratory and metabolic responses to submaximal work loads indicate that the low intensity exercise regimen was capable of inducing some of the known adaptations of exercise training such as a decrease in plasma insulin and norepinephrine concentrations during exercise, reductions in heart rate, pulmonary ventilation and blood lactate concentration at a given exercise intensity, and an increase in skeletal muscle oxidative capacity. The energy cost of sitting and standing was not decreased in spite of the loss in body mass. However, the energy cost of submaximal cycling and walking exercises was reduced considerably. These results clearly demonstrate that it is quite possible to lose fat while preserving fat-free mass through regular prolonged exercise of moderate intensity if energy intake is kept constant at baseline level. They also emphasize the importance of the individual differences in response to negative energy balance.

Adult↗
PubMed1990

Long-term exercise training with constant energy intake. 2: Effect on glucose metabolism and resting energy expenditure.

The effect of exercise training on glucose and insulin metabolism as well as on resting energy expenditure was investigated in five young men (mean BMI = 27.5 +/- 2.9 (s.d)). Subjects performed cycle-ergometer exercise 6 days/week over a 100 day period and the quantity of daily exercise was calculated to induce a 4.2 MJ/day surplus in energy expenditure during the days of training. As expected, significant weight and fat losses were observed in response to the training program. Exercise training induced a significant reduction in fasting levels and in the responses of insulin to a 4.2 MJ meal or an oral glucose load. Most of the training effects were noted after only 25 days of training. However, a significant decrease in plasma C-peptide concentrations during the oral glucose tolerance test was observed only at the end of the exercise program whereas essentially no change occurred during the first 25 days of training. The resting metabolic rate (RMR) and the thermic effect of food (TEF) were not significantly modified by training. Results show that the reduction in plasma insulin induced by training occurred earlier than that for C-peptide. Moreover, the absence of change in RMR in the presence of a substantial weight loss may represent a beneficial effect of training in comparison to the documented effect of diet-induced weight loss on RMR.

Adult↗
PubMed1990

Genetic effects in the response of adipose tissue lipoprotein lipase activity to prolonged exercise. A twin study.

Our laboratory has reported large inter-individual differences in the metabolic response of adipose tissue to prolonged exercise in humans. The present study investigated the contribution of heredity in the metabolic changes of adipose tissue to prolonged exercise in 11 monozygotic and 10 dizygotic pairs of male twins, 18 to 27 years of age, studied immediately before and after a 90 min bout of exercise. The sum of 7 skinfold thicknesses and percent of fat from underwater weighing were used as body fat indicators (BFI). Subcutaneous adipose tissue was excised and fat cell weight (FCW) determined. The activity of adipose tissue lipoprotein lipase (LPL) released with heparin was also measured. BFI and FCW were identical in both types of twins. As previously reported, LPL activity was increased by exercise (P less than 0.01) in both type of twins. The changes observed for LPL activity were more similar in monozygotic twins than in dizygotic twins resulting in a significant level of inheritance (P less than 0.05). A genetic component for LPL activity supports the hypothesis that adipose tissue LPL could be genetically determined not only in its basal activity but also in response to stresses such as exercise.

Adipose Tissue↗
PubMed1990

Genetic effects in human energy expenditure components.

It is increasingly recognized that variations in human energy expenditure are partly due to an influence of the genotype, even after control for the well established concomitants of energy expenditure. Using the technique of genetic epidemiology, we have found that about 40 percent of the variance in resting metabolic rate, thermic effect of food and energy cost of low to moderate intensity exercise (less than or equal to 5 times the resting metabolic rate) is explained by inherited characteristics. A significant genetic effect has also been reported for the level of habitual physical activity. The existence of a genotype-environment interaction has also been investigated. Thus, we have demonstrated that in response to chronic overfeeding, as well as negative energy balance, changes in the components of energy expenditure are partly determined by one's genotype. Taken as a whole, these observations consistently support the hypothesis that heredity plays a significant role on the variations in the various components of energy expenditure in humans. Further research should now be focused more on the identification of biochemical and molecular markers of these energy expenditure characteristics.

Adult↗
PubMed1990

Commingling and segregation analysis of blood pressure in a French-Canadian population.

Commingling and segregation of age-sex-adjusted systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial blood pressure (MBP) were examined in 1,560 individuals from 374 French-Canadian nuclear families. After correction for skewness, evidence in favor of two commingled distributions was found for SBP in the combined data (parents and offspring) and in parents, but not in offspring. Segregation analysis (using the computer program POINTER) suggested that a multifactorial contribution to all three phenotypes was greater in offspring than in parents, which could be the result of either polygenic or shared environmental components relevant to sibships, or both. Statistical evidence was found for a major effect on SBP. However, Mendelian transmission of the major effect was rejected, and no transmission of the major effect (equal tau's) was not. This is just the opposite to what would be expected if the major effect was due to a major gene, and it would ordinarily be considered as sufficient evidence to refute a major gene effect on SBP. However, the commingling in parents but not in offspring (who are all below 26 years of age), and the finding of equal transmission probabilities (nearly equal to 1), are compatible with an alternative interpretation. It is possible that there is a real major gene effect on SBP but that the genotype for elevated SBP has not yet expressed itself in the offspring as they have not yet gone through the risk period. Accordingly, this possibility needs to be evaluated further in additional studies involving older offspring.

Blood Pressure↗
PubMed1990

Long-term exercise training with constant energy intake. 3: Effects on plasma lipoprotein levels.

The composition and concentration of plasma lipoproteins were studied in five young men (mean BMI = 27.5 +/- 2.9 (s.d.] before, during (after 25 and 50 days of training), and after the completion of a 100 day exercise training program that induced daily 4.2 MJ calorie deficit. Along with reductions in body weight (from 86.7 +/- 20.0 to 78.7 +/- 17.1 kg, P less than 0.01) and in fat mass (from 17.0 +/- 9.7 to 10.4 +/- 7.4 kg, P less than 0.01), the exercise training program induced numerous changes in plasma lipoprotein levels. Plasma total cholesterol level fell significantly after 25 days of training (P less than 0.05) and remained significantly reduced at the end of the training experiment (P less than 0.05). This reduction in total plasma cholesterol was accompanied by reductions in plasma apoprotein (apo) B, LDL-cholesterol and LDL-apo B levels (P less than 0.05). There were trends for reductions in plasma triglyceride and VLDL components that were significant only for VLDL-triglycerides (P less than 0.05). Plasma HDL-cholesterol levels increased significantly only at the end of the training program (P less than 0.01). This increase in plasma HDL-cholesterol was not accompanied by an increase in plasma apo A-I levels suggesting that exercise training produced an increase in HDL cholesterol content rather than an increase in HDL particle number. Ratios of HDL-cholesterol/cholesterol (P less than 0.01) and apo A-I/apo B (P less than 0.05) were significantly increased by exercise training, suggesting a decreased risk of cardiovascular disease. These results indicate that a reduction in fat mass solely induced by aerobic exercise training has substantial beneficial effects on plasma lipoprotein levels.

Adult↗
PubMed1990

Associations between regional body fat distribution, fasting plasma free fatty acid levels and glucose tolerance in premenopausal women.

The associations between total adiposity, body fat distribution measured by computed tomography (CT) and estimated by the waist-to-hip ratio (WHR), regional fat cell morphology, fasting plasma free fatty acid (FFA) levels and glucose tolerance were studied in a sample of 37 premenopausal women aged 35.3 +/- 4.6 years (mean +/- s.d.). Body fat mass, CT-derived abdominal and femoral fat areas, as well as the abdominal fat cell weight were all significantly associated with fasting plasma FFA levels (0.34 less than r less than 0.49, 0.005 less than P less than 0.05), and with the glucose and insulin areas during the oral glucose tolerance test (OGTT) (0.36 less than r less than 0.70, 0.0001 less than P less than 0.05). No associations were found between the WHR, the femoral fat cell weight and fasting plasma FFA levels or glucose area during the OGTT. However, the WHR and the femoral fat cell weight were positively associated with insulin area. Plasma FFA levels were positively correlated with the glucose area during the OGTT, whereas no association was found between plasma FFA levels and the insulin area. Covariance analysis indicated that this effect of plasma FFA levels on the magnitude of glucose response to OGTT was independent from that of total adiposity or regional body fat distribution variables. These results emphasize the importance of plasma FFA levels as a correlate of glucose tolerance and suggest that the associations previously reported between obesity, regional body fat distribution, fat cell size and glucose tolerance are, at least partly, mediated by variations in plasma FFA levels.

Abdomen↗
PubMed1990

Apolipoprotein E polymorphism alters the association between body fatness and plasma lipoproteins in women.

The aim of the present study was to investigate the associations between total adiposity, body fat distribution, and plasma lipoprotein levels within groups of women defined on the basis of apolipoprotein E phenotypes, in order to verify whether apoE polymorphism could modify these associations. In women having only apolipoprotein E3 isoforms (n = 24), body fat mass, the waist: hip circumference ratio, and computed tomography-derived total and intra-abdominal fat areas were all positively correlated with very low density lipoprotein (VLDL) and low density lipoprotein (LDL) lipids and apolipoprotein B concentrations. These body fatness variables were also negatively correlated with plasma high density lipoprotein (HDL) cholesterol concentration. These associations were, however, altered in the groups of women carrying either apoE2 or E4 isoforms. Indeed, in women carrying the apoE2 isoform (n = 22), body fatness variables were predominantly associated with VLDL components concentration (0.05 greater than P less than 0.01) and with LDL triglyceride content. No association was found between adiposity and LDL cholesterol or apolipoprotein B levels in these women. In contrast, no relationship was found between total adiposity, regional fat accumulation, and VLDL fraction in women carrying the apolipoprotein E4 isoform (n = 17). In this latter group, computed tomography-measured total abdominal fat accumulation was positively correlated with LDL apolipoprotein B (r = 0.58, P less than 0.05) concentration, whereas intra-abdominal fat accumulation was positively correlated with both LDL cholesterol and apolipoprotein B concentrations (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1990

Anaerobic performances in black and white subjects.

The anaerobic performance characteristics of 15 Black males of African ancestry (25 +/- 2 yr; mean +/- SD) and 17 White males of French Canadian ancestry (22 +/- 2 yr) were compared. All subjects were sedentary. Morphological characteristics and body composition were similar in both groups. They were tested for maximal force during voluntary isometric contraction of the knee extensors and for total work output during 10 s, 30 s, and 90 s of maximal and repetitive knee extensions. Results indicated no significant differences between Blacks and Whites in maximal force of the knee extensors (736 +/- 78 N vs 722 +/- 11 N, respectively) and in total work output during the 10-s (1134 +/- 246 J vs 1124 +/- 207 J) and 30-s (2735 +/- 519 J vs 2779 +/- 647 J) tests. There was a difference of about 400 J between Blacks and Whites in the total work output during the 90-s test, but this difference was not statistically significant. However, significant differences were found between Blacks and Whites in the peak power output decrement during the last 60 s of the 90-s anaerobic test. These differences in peak power output between the two groups ranged between 7 and 10 W during the last 30 s of the 90-s test. The results indicate that knee extensor muscles of sedentary Black and White males have similar anaerobic performance power and capacities. However, the results reveal that sedentary Black subjects experience a greater degree of fatigue than sedentary Whites during an anaerobic exercise lasting longer than 30 s.

Adult↗
PubMed1989

Cardiovascular risk factors in a French Canadian population: resolution of genetic and familial environmental effects on blood pressure using twins, adoptees, and extensive information on environmental correlates.

Genetic and environmental influences on systolic (SBP), diastolic (DBP), and mean arterial (MBP) blood pressure were examined using an expanded version of a path model in which parents and their singleton, twin, and adopted offspring were incorporated, and which also included an environmental index as an estimate of the underlying familial environmental component. Estimates of genetic heritability are lower in parents (10-15%) than in offspring (40-50%). Cultural heritability was significant for SBP (0.31) and MBP (0.40), and an intergenerational effect was found for DBP, with higher estimates in parents (0.42) than in offspring (0.21). Marital resemblance was significant, and no support was found for differential maternal and paternal cultural transmission. Two novel results arising from this study are 1) gender-specific sibling effects, with greater female than male resemblance for SBP and MBP and the opposite pattern for DBP, and 2) the suggestion of extra twin resemblance arising on account of additional shared environments and resulting in greater like-sex than opposite-sex twin resemblance. The major conclusions drawn from this study are that 1) parameter estimates are stable with or without the use of extensive environmental indices, and 2) the addition of twins and adoptees did not significantly impact the results, with the exception of a possible influence of the adoptees in estimates of cultural heritability for DBP. Combining both these features (i.e., extended relatives and environmental indices) enables testing for additional sources of familial aggregation, which is not possible using the traditional nuclear family approach and results in a more accurate assessment of the relative roles of heredity and environment on blood pressure than has been previously possible.

Adolescent↗
PubMed1989

Familial lipoprotein lipase-activity deficiency: study of total body fatness and subcutaneous fat tissue distribution.

Total body fatness and subcutaneous fat tissue distribution were evaluated in 19 hyperchylomicronemic patients. Eleven were males, aged 10 to 57 years, and eight were females, aged 13 to 46 years. Familial lipoprotein-lipase-activity deficiency was diagnosed by the absence of lipoprotein-lipase activity in the plasma withdrawn ten and 20 minutes after intravenous injection of ten units of heparin per kilogram of body weight. The 19 patients had skin-fold measurements for evaluation of subcutaneous fat distribution. Fifteen also underwent body density measurements by underwater weighing. Percent body fat was calculated from body density. These anthropometric data were plotted against the regression curves of 1638 normal controls of both sexes (aged 10 to 54 years) for fat tissue weight, percent body fat, subcutaneous fat/total fat mass ratio and trunk/extremity skin-fold ratio. Impairments in the process of building fat tissue reserves could not be shown in the 19 hyperchylomicronemic patients, in spite of the absence of lipoprotein-lipase activity in their postheparin plasma. It is hypothesized that normal fat tissue mass in these patients could be due partly to de novo synthesis of fatty acids by adipocytes, hydrolysis of plasma triglycerides by hepatic lipase, and/or contribution of a specific fat-tissue lipase to the catabolism of plasma triglyceride-rich lipoproteins.

Adipose Tissue↗
PubMed1989

Genetic effect in resting and exercise metabolic rates.

Two studies dealing with the contribution of the genotype in individual differences for resting metabolic rate (RMR), thermic effect of a 4.2 MJ carbohydrate meal (TEM), and energy cost of submaximal exercise are reported. The genetic effect for RMR and TEM was studied in 31 pairs of parent-child, 21 pairs of dizygotic (DZ) twins, and 37 pairs of monozygotic (MZ) twins, whereas the heritability of the energy cost of submaximal exercise was determined from data on 22 pairs of DZ twins and 31 pairs of MZ twins. The heritability of RMR reached approximately 40% of the variance remaining after adjustment for age, gender, and fat-free mass, (FFM). The genetic effect for TEM was equivalent to at least 40% to 50% of the variation in the energy expended during four hours after the meal test. A highly significant genetic effect was found for fasting plasma glucose (greater than .72), but the results for fasting plasma insulin are unclear. No significant genetic variance was seen for the glucose and insulin response to the carbohydrate meal. Finally, heritability for the metabolic rate during cycle exercise was high (greater than or equal to .46) at low power output, but it became nonsignificant when the energy cost reached about 6 times the RMR.

Adolescent↗
PubMed1989

Computed tomography-measured trunk fat and plasma lipoprotein levels in nonobese women.

The associations between total adiposity, adipose tissue distribution measured by computed axial tomography (CAT), regional variation in fat cell size, and plasma lipoprotein levels were studied in a sample of 22 premenopausal healthy nonobese women aged 34.6 +/- 3.1 years (mean +/- SD) (% body fat, 27.8 +/- 5.8). In these nonobese women, no associations were found between total adiposity, adipose tissue distribution, and plasma triglyceride or very-low-density lipoprotein levels. However, total adiposity (as reflected by the body density-derived fat mass and by the adipose tissue volume measured by CAT), as well as the total trunk fat areas (measured at the abdominal and thoracic levels) were positively correlated with plasma low-density lipoprotein (LDL) cholesterol (.05 greater than P less than .01) and LDL apolipoprotein (apo) B (.05 greater than P less than .0005) levels. Because of these associations with LDL-C and LDL apo B levels, these body fatness indicators were negatively correlated with the HDL-cholesterol/LDL-cholesterol and HDL-apo A-I/LDL-apo B ratios. However, few significant associations were observed between the proportion of abdominal fat estimated by the waist/hip circumference ratio (WHR) and the lipoprotein-lipid profile (r = .45 and r = .44, P less than .05 with HDL triglyceride (TG) and LDL-apo B/LDL-cholesterol ratio, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1989

Genetic factors in obesity.

Several points should be emphasized in summarizing the role of biological inheritance in human body-fat variation. First, at least two kinds of genetic effects must be considered: the additive genetic effect and the genotype-environment interaction effect. Second, from the data reviewed here, we conclude that the additive genetic effect in amount of subcutaneous fat is quite low but that it is higher (around 25 to 30 per cent) for fat mass and regional fat distribution. These results suggest that visceral fat, perhaps, is more influenced by the genotype than subcutaneous fat. Third, it appears that a genotype-overfeeding interaction component exists for body fat, which suggests that sensitivity of individuals to changes in body fat following overfeeding are genotype-dependent. Fourth, the limited data available suggest that the genotype accounts for a significant fraction (equal to or greater than 40 per cent) of the individual differences in RMR, TEM, and TEE. Fifth, one finds a slight genetic effect for the proportion of protein, fat, and carbohydrate in the diet. Sixth, there is some indication that individual differences in habitual physical activity level are characterized by a significant genetic component. The search for genetic markers of the various obesity phenotypes has not been initiated to any extent at this time. However, one can anticipate considerable development in this area in the coming decade.

Adipose Tissue↗
PubMed1989

Assessment of adipose tissue distribution by computed axial tomography in obese women: association with body density and anthropometric measurements.

1. Abdominal obesity is associated with numerous metabolic complications. Deep abdominal adipose tissue is critical in the association between the level of abdominal obesity and cardiovascular risk factors. 2. Adipose tissue localization was assessed by computed axial tomography (CAT), and its association with body density and anthropometric measurements was investigated in a sample of fifty-one obese women (percentage body fat 45.9 (SD 5.6)) aged 35.7 (SD 5.5) years. The CAT scans were performed at three levels: lower chest, abdomen and mid-thigh. 3. The total adipose tissue volume computed from these three scans was highly correlated with body fat mass (r 0.94, P less than 0.001). The proportion of deep abdominal fat as measured by the ratio of deep: total adipose tissue areas at the abdominal level was not significantly correlated with body fat mass, but it was moderately associated with the ratio of waist: hip circumferences (WHR) (r 0.49, P less than 0.001). The absolute amount of deep abdominal fat was, however, significantly correlated with body fat mass (r 0.72, P less than 0.001). 4. The subscapular (r 0.38) and the abdominal (r 0.38) skinfolds were the only two skinfolds that were significantly associated with the proportion of deep abdominal fat (P less than 0.01). These skinfolds were also those which showed the highest correlation with the absolute amount of deep abdominal fat (r 0.65, P less than 0.001, for both skinfolds). 5. A three-site CAT-scan procedure can be used for the estimation of body fat mass in premenopausal obese women. 6. In these obese women, there was no significant association between total adiposity and the proportion of deep adipose tissue at the abdominal level. 7. In premenopausal obese women, the absolute amount of deep abdominal fat can be predicted from anthropometric measurements with more accuracy than the relative amount of deep abdominal fat.

Adipose Tissue↗