Showing papers by "Claude Bouchard published in 1988"

Inheritance of the amount and distribution of human body fat.

Abstract: Despite recent advances, controversy continues about the inheritance of the amount and distribution of body fat. We have studied the genetic and 'cultural' (nongenetic) transmission between generations of the body mass index, sum of six skinfold measurements, percentage of body fat, fat mass, fat-free mass, and two indicators of fat distribution. These data were obtained in 1698 members of 409 families, which included the following pairs of family members: spouses, (maximum number of pairs = 348), foster parent-adopted child (322), siblings by adoption (120), first-degree cousins (95), uncle/aunt-nephew/niece (88), parent-natural child (1239), full sibs (370), dizygotic twins (69), and monozygotic twins (87). The total transmissible variance ranged from about 40 percent for the amount of subcutaneous fat to 60 percent for the pattern of subcutaneous fat distribution. Biological inheritance accounted for only 5 percent of the variance for subcutaneous fat and the body mass index, but 20 to 30 percent for the percentage of body fat, fat mass, fat-free mass, and fat distribution. These data suggest that the amount of internal fat is influenced by heredity more than the amount of subcutaneous fat. Furthermore, we consistently found that nongenetic influences are quite important in determining the amount and distribution of body fat in the population. These estimates may differ in the subpopulation of obese individuals.

Estimation of the contribution of the various energy systems during maximal work of short duration.

Abstract: The aim of this experiment was to estimate the relative contribution of the various energy delivery systems during maximal exercise tests of short duration. Twenty-five males were submitted to a VO2max test and 10-, 30-, and 90-s maximal ergocycle tests. Expiratory gases were collected with a Douglas bag during the entire 30-s test and continuously monitored with an open-circuit system during the 90-s test. Estimates of the phosphagenic component represented approximately 55%-60% of the energy expenditure during the 10-s work performance. Results of the 30-s test indicated that the relative contributions of the energy systems were 23%, 49%, and 28% for the phosphagenic, glycolytic, and oxidative pathways, respectively. For the 90-s test, these estimates were 12%, 42%, and 46% for the three metabolic systems. The highest contribution of each system during the 90-s was obtained from 5 to 15 s for the phosphagenic component, from 16 to 30 s for the glycolytic, and from 61 to 75 s for the aerobic energy systems. During the 90-s test, VO2max was reached after approximately 60 s. It is concluded that the 30 and 90 s are not strictly anaerobic although they all have a large anaerobic component.

Heredity and body fat

Abstract: The genetics of human obesity was reviewed here in terms of studies dealing with body fat and fat distribution. The role of heredity was examined by reviewing genetic disorders in which obesity is a clinical feature. Two kinds of genetic effects were discussed: the additive genetic effect and the genotype-environment interaction effect. Several indicators of body fat exist, including body mass index, amount of subcutaneous fat, percentage body fat, fat mass, regional fat distribution, and subcutaneous fat pattern. A low additive genetic effect of less than 10% of human phenotypic variation is found in body mass index and amount of subcutaneous fat, while percentage body fat, fat mass, fat distribution, and fat patterning are characterized by heritability estimates of about 25%. On the other hand, a recent study demonstrates that there is an important genotype-environment interaction effect in human body fat variation induced by overfeeding. Limitations of current approaches to the study of the genetics of human body fat and obesity are considered and comments are offered concerning promising areas of future research.

Heredity and changes in plasma lipids and lipoproteins after short-term exercise training in men.

Abstract: The aims of this controlled experiment were to investigate the effects of short-term aerobic exercise training on plasma lipid and lipoprotein concentrations and the role of heredity in determining the individual variation observed in the lipoprotein-lipid response. Six pairs of male monozygotic (MZ) twins were subjected to an exercise training program that induced a 22,000 kcal energy deficit after 22 consecutive days of training. This program significantly reduced body weight, percent body fat, and subcutaneous fat and significantly increased maximal oxygen consumption (VO2max) (p less than 0.005). The plasma insulin response to an oral glucose challenge was markedly reduced after training (p less than 0.001). Plasma triglyceride concentration decreased and the high density lipoprotein cholesterol (HDL-CHOL)/CHOL ratio increased with training (p less than 0.05). Subjects also displayed substantial individual variation in their response to exercise training, but the changes in plasma CHOL, apolipoprotein (apo) B low density lipoprotein cholesterol (LDL-CHOL), HDL-CHOL, and the HDL-CHOL/CHOL ratio tended to be similar within MZ twin pairs (0.67 less than or equal to ri less than or equal to 0.92; 0.05 greater than p less than 0.0001) thus indicating a significant effect of heredity on the sensitivity of plasma lipids and lipoproteins to exercise training.(ABSTRACT TRUNCATED AT 250 WORDS)

Inter-generation transmission of physical fitness in the Canadian population.

Abstract: Body weight, height, body mass index, skinfold measurements, waist-to-hip ratio (WHR), somatotype components, muscular endurance and strength, flexibility, resting heart rate and submaximal power output (PWC150/kg) were measured in 13,804 subjects during the 1981 Canada Fitness Survey. Familial correlations were computed to determine the contribution of transmissible (t2) and environmental (e2) factors in physical fitness by path analysis. Transmissibility estimates (t2) under 0.30 for weight, height, WHR and PWC150/kg, above 0.40 for mesomorphy, ectomorphy, push-up test and flexibility, and between 0.30 and 0.40 for the other measurements were obtained. These results suggest that e2 account for more than 50% of the variation and that the average total biological and cultural inheritance from parents to offspring in physical fitness of Canadians accounts for 30% to 40% of the phenotypic variation.

Abdominal adipose tissue and serum HDL-cholesterol: association independent from obesity and serum triglyceride concentration.

Abstract: It has been recently shown that an excess of abdominal fat was associated with reduced serum HDL-cholesterol level, supporting previous studies that have reported a relationship between fat distribution and cardiovascular risk factors. Since a negative relationship has been observed between serum triglyceride and HDL-cholesterol concentrations, the associations between body fat distribution and HDL-cholesterol level was studied with control over serum triglycerides in a sample of 429 healthy adult men. The relative distribution of subcutaneous fat, as reflected by the trunk to extremity skinfolds (T/E) ratio and the absolute amount of subcutaneous abdominal fat, obtained by the measurement of the abdominal skinfold thickness, were significantly correlated with serum triglycerides (r = 0.27 and 0.35 respectively, P less than 0.0001), with serum HDL-cholesterol (r = -0.14, P less than 0.01, and -0.26, P less than 0.0001) and with the serum HDL-cholesterol/total cholesterol ratio (r = -0.25 and -0.39, P less than 0.0001). Analysis of variance on two factors, the T/E ratio and the body mass index (BMI), revealed significant and independent effects of adiposity and relative distribution of subcutaneous fat on serum lipids and HDL-cholesterol (0.05 greater than P less than 0.001). However, when comparable analyses of variance were performed to study the respective contributions of obesity (as measured by the BMI) and the absolute amount of abdominal fat (as measured by the abdominal skinfold), most of the variance in serum triglycerides, cholesterol and HDL-cholesterol was explained by abdominal fat alone and not by the BMI. Therefore, it appeared that with the exception of the HDL-cholesterol/total cholesterol ratio, the association between obesity and serum lipids and HDL-cholesterol was, in the present sample, primarily explained by the amount of abdominal fat. As reported by others, serum triglyceride level was negatively correlated with HDL-cholesterol (r = -0.33, P less than 0.0001) and the HDL-cholesterol/total cholesterol ratio (r = -0.54, P less than 0.0001). After cholesterol and HDL-cholesterol scores were adjusted for the effect of triglycerides, the T/E ratio was no longer associated with serum HDL-cholesterol whereas the abdominal skinfold remained significantly correlated with serum HDL-cholesterol concentration (r = -0.16, P less than 0.01). These results suggest that a portion of the association between body fat topography and serum HDL-cholesterol is mediated by the effect of fat distribution on serum triglycerides.(ABSTRACT TRUNCATED AT 400 WORDS)

Sensitivity to overfeeding: the Quebec experiment with identical twins.

Abstract: The role of the genotype in the response to short-term overfeeding was assessed by submitted six pairs of male monozygotic twins to a 4.2 MJ (1000 kcal) per day energy intake surplus for a period of 22 consecutive days. Individual differences in fat mass and fat-free mass gains were observed in response to overfeeding but they were not randomly distributed. Indeed, the within-pair resemblance in the response was striking when compared to the heterogeneity found among the pairs in adiposity and fat-free mass gains. The intrapair resemblance in the response to overfeeding as assessed by the intraclass coefficient computed with the individual changes, reached 0.88 for total fat mass and 0.76 for fat-free mass. A similar trend for a genetically determined pattern of adaptation to overfeeding was observed for resting metabolic rate (intraclass = 0.63), thermic effect of a meal (intraclass = 0.62), and energy cost of submaximal exercise (intraclass = 0.78) when the data were analysed in terms of changes in oxygen uptake. On the other hand, no major alterations in glucose and insulin response to a glucose load or a test meal, in cardio-pulmonary adaptation to submaximal exercise and in maximal exercise tolerance were found with overfeeding. In contrast, the response of suprailiac fat cell lipolysis (intraclass of about 0.7) and heparin releasable adipose tissue lipoprotein lipase (intraclass - 0.82) varied among individuals but was highly homogeneous within genotypes. Similarly, a genotype-overfeeding interaction effect was seen for serum triglycerides (intraclass = 0.69), HDL-cholesterol (intraclass = 0.85), and the HDL-cholesterol to total cholesterol ratio (intraclass = 0.82). Multiple correlation analyses suggest that much of the variance in the response of fat mass (R = 0.65) and fat-free mass (R = 0.81) is accounted for by alterations in the energy expenditure components assessed in the study. If one takes into account the measurement errors always present in such complex studies and the fact that only a limited fraction of the energy expenditure of activity was considered by design, one can conclude that the genotype determines to a large extent the response variation to short-term overfeeding. In particular, the genotype-overfeeding interaction effect for body composition changes seems to be mediated by the various energy expenditure components, themselves characterized by significant genotype-overfeeding interaction effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Racial variation in work capacities and powers.

Abstract: Large interindividual variation in work capacities and powers are often reported in the literature. The variations are attributed to such varied factors as age, sex, exercise training, and heredity, among others. Ethnic/racial origin as a putative causal factor of such variations has also been considered. Studies of subjects from various countries report aerobic power generally between 40 and 50 mL O2/kg.min-1, with a mean around 45 mL. Differences between groups are generally small and genuine racial differences in maximal aerobic power are lacking when allowance is made for other factors. There are, on the other hand, differences between racial groups in submaximal work efficiency and endurance performance. These differences, however, appear to result from differences in mechanical efficiency owing to test mode and/or level of habituation to the ergometer. Performances on maximal tests of short duration demonstrate some variation among racial groups, but again differences in mechanical efficiency cannot be ruled out. Thus there does not appear to be valid and reliable evidence to support the concept of clear racial differences in work capacities and powers.

Absence of charge variants in human skeletal muscle enzymes of the glycolytic pathway.

Abstract: Phenotypes of various glycolytic enzymes were determined in muscle biopsies. The results suggest that genetic effects on maximal enzyme activities may be associated with regulatory elements of the appropriate genes.