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Biomedical subjects

A Tremblay

Publications and source records attributed to A Tremblay.

At least 163 records · Page 9Linked to original sources
PubMed1996

A single threshold value of waist girth identifies normal-weight and overweight subjects with excess visceral adipose tissue.

Our objective was to determine threshold values of waist girth, waist-to-hip ratio (WHR), and sagittal diameter corresponding to an accumulation of visceral adipose tissue of 130 cm2 and to verify whether these threshold values could be influenced by sex, age, menopausal status, and the degree of obesity. From the regression equations computed in the total sample of 213 men [aged (mean+/- SD) 37.8 +/- 12.2 y] and 190 women (aged 37.3 +/- 12.1 y), a waist girth of approximately 95 cm in both sexes, WHR values of 0.94 in men and of 0.88 in women, and sagittal diameters of 22.8 cm in men and 25.2 cm in women corresponded to a visceral adipose tissue area of 130 cm2. In both sexes, threshold values of waist girth corresponding to critical amounts of visceral adipose tissue were generally lower in subjects who were > or = 40 y old (approximately 90 cm) than in younger individuals (approximately 100 cm). Similar differences were found for WHR and sagittal diameter threshold values. Finally, threshold values of waist girth corresponding to critical amounts of visceral adipose tissue were essentially similar in normal-weight and overweight men and women, whereas threshold values of WHR were in general higher in normal-weight than in overweight subjects. In conclusion, our results suggest that the relations of anthropometric variables to visceral adipose tissue accumulation are age-specific. However, waist girth is likely to be a more convenient anthropometric correlate of visceral adipose tissue than the WHR because threshold values of waist girth corresponding to critical amounts of visceral adipose tissue do not appear to be influenced by sex or by the degree of obesity.

Adipose Tissue↗
PubMed1996

Reproducibility of 24-h energy expenditure and macronutrient oxidation rates in an indirect calorimeter.

The maintenance of weight and adipose tissue mass in humans appears to be related to a balance between the rates of oxidation and consumption of macronutrients; yet, little evidence is available on the reproducibility of 24-h macronutrient oxidation rates and how this relates to diet in the days preceding a chamber session. This study examined the reproducibility of 24-h macronutrient oxidation rates, 24-h energy expenditure (EE), and respiratory quotient (RQ) in 30 adults who ate their habitual diets before two 24-h whole body indirect calorimeter sessions. Results showed that the within-subject coefficients of variation (CVws) for 24-h EE and RQ were 2.8 and 2.6%, respectively. CVws for macronutrient oxidations ranged from approximately 15 to 25%. Means comparisons of 24-h EE, RQ, and macronutrient oxidation rates between sessions showed no significant differences, and all variables had significant positive intraclass correlation coefficients (P < 0.05). In conclusion, macronutrient oxidations all showed significant reproducibility for the group and a significant but lower reproducibility for individuals when habitual diet and activity preceded the experimental sessions.

Adipose Tissue↗
PubMed1996

Effects of exercise training on abdominal obesity and related metabolic complications.

Excessive deposition of visceral adipose tissue is known to predispose to cardiovascular diseases. Considerable epidemiological and experimental evidence suggests that many physiological factors are involved in the aetiology of premature atherosclerosis associated with visceral obesity. Insulin resistance is frequently associated with abdominal obesity, and probably plays an important role in the pathophysiology of hypertriglyceridaemia, low levels of plasma high-density lipoprotein (HDL)-cholesterol, hypertension and reduced fibrinolytic activity. Exercise training may counteract the aberrant metabolic profile associated with abdominal obesity both directly and as a consequence of body fat loss. Exercise may increase insulin sensitivity, favourably alter the plasma lipoprotein profile and improve fibrinolytic activity. Changes in the activity of insulin-sensitive glucose transporters and of skeletal muscle lipoprotein lipase are some of the possible explanations for the increased insulin sensitivity and improved blood lipid profile associated with regular exercise. This review presents physical training as a relevant nonpharmacological tool in the treatment of abdominal obesity and associated metabolic disorders. The impact of regular exercise on the different aspects of the insulin resistance syndrome is discussed. The roles of gender, age and the state of insulin resistance on the metabolic effect of physical training are also considered.

Abdomen↗
PubMed1996

Seven-year changes in body fat and visceral adipose tissue in women. Association with indexes of plasma glucose-insulin homeostasis.

OBJECTIVE: To study the associations between changes in body fatness, visceral adipose tissue (AT), and indexes of plasma glucose-insulin homeostasis over a 7-year follow-up period. RESEARCH DESIGN AND METHODS: A sample of 30 nondiabetic women aged 35.2 +/- 5.6 (SD) years at baseline was studied. RESULTS: Changes in visceral AT and in subcutaneous AT (measured by computed tomography) as well as changes in body fat mass (obtained by hydrostatic weighting) were significantly related to changes in fasting plasma insulin levels and in plasma insulin area measured after a 75-g oral glucose load (0.47 < or = r < or = 0.62; P < 0.01). Changes in visceral AT but not in body fat mass or in subcutaneous AT area were significantly associated with changes in plasma glucose area (r = 0.37; P < 0.05). When two subgroups of women with similar mean increases in body fat mass but with either small or large increases in visceral AT were compared, the subgroup with the largest gain in visceral AT showed the greatest deterioration in indexes of plasma glucose-insulin homeostasis. On the other hand, when two subgroups with similar mean increases in visceral AT but with different changes in body fat mass were compared, both subgroups showed similar changes in plasma glucose and insulin concentrations. CONCLUSIONS: Results of this 7-year follow-up study in women suggest that changes in indexes of plasma glucose-insulin homeostasis are significantly associated with changes in visceral AT, even after control for changes in body fat mass.

Adipose Tissue↗
PubMed1996

A case study on energy balance during an expedition through Greenland.

A 59-year-old man who had always been lean was submitted to overfeeding for two months in preparation for a 3-week expedition through Greenland, during which a considerable negative energy balance was expected. The overfeeding protocol consisted of an estimated energy surplus of 2000 kJ per day and this induced body weight and fat gains of 4.7 and 3.6 kg, respectively. Whole-body indirect calorimetry measurements following 4 and 8 weeks of overfeeding showed that there was no change in the subject's daily energy expenditure. Ad libitum energy intake measured during a buffet-type meal was substantially increased during overfeeding. As expected, the expedition induced a negative energy balance which reduced body weight below the pre-overfeeding level. Daily energy expenditure measured 12 days after the expedition, when the subject had recovered his initial body weight, was decreased by 1.4 MJ/day. The increase in ad libitum energy intake observed during the pre-expedition overfeeding persisted after the expedition. These adaptations tended to persist three weeks and four months after the end of the expedition. These results suggest that both energy expenditure and intake were modified after the expedition to prevent a subsequent body energy deficit.

Body Composition↗
PubMed1996

Anthropometric correlates to changes in visceral adipose tissue over 7 years in women.

OBJECTIVE: To investigate the association between either increases or decreases in visceral adipose tissue and changes in anthropometric indices in a group of 32 women studied over a 7-y period. SUBJECTS: 32 women aged 35.1 +/- 5.4 (SD) years at baseline. MEASUREMENTS: Waist and hip circumferences, body fat mass (hydrostatic weighing) and viscera adipose tissue (computed tomography) were measured at baseline and at follow-up. RESULTS: Waist girth, waist-to-hip ratio, sagittal diameter and visceral adipose tissue area were all significantly higher at follow-up than at baseline (p < 0.05). Changes in visceral adipose tissue area were strongly correlated to changes in waist girth, hip girth, sagittal diameter and body fat mass (0.80 < or = r < or = 0.91 p < 0.0001). However, the association between changes in waist-to-hip ratio and those in visceral adipose tissue area was of low magnitude (r = 0.35; p = 0.05). Partial correlation analyses showed that the association between changes in visceral adipose tissue area and changes in either waist girth (p < 0.01) or sagittal diameter (p < 0.0001) remained significant even after control for 7-y variation in total body fatness. CONCLUSION: Results of the present study suggest that changes in visceral adipose tissue accumulation that occur with age in women are better predicted by changes in waist girth or sagittal diameter than by changes in waist-to-hip ratio.

Adipose Tissue↗
PubMed1996

Insulin and glucagon responses to adrenaline infusion in abdominal obese men.

OBJECTIVE: To investigate the hormonal, cardiovascular and metabolic responses of visceral vs subcutaneous obese men to infused adrenaline. DESIGN: Intervention study of an hour adrenaline infusion (0.01 micrograms/kg fat-free mass/min). SUBJECTS: Eighteen moderately obese men (age: 30-40 y, BMI: 28-34 kg/m2) divided according to their degree (low vs high) of visceral adipose tissue (AT) accumulation. MEASUREMENTS: Various fatness and fat distribution variables (computed tomography and anthropometry), heart rate and blood pressure, plasma concentrations of gluco-regulatory hormones, glucose, glycerol and free fatty acids (FFA). RESULTS: Similar increases were noted in heart rate, plasma adrenaline, FFA and glycerol levels in both low and high visceral AT groups after hormonal infusion. There was a tendency for plasma glucagon responses to be higher in men with high amounts of visceral fat (p = 0.07). Plasma glucose levels increased in both groups, but significantly more in men with low levels of visceral AT (p < 0.05), whereas plasma insulin concentrations increased significantly only in men with high amounts of visceral AT in response to adrenaline infusion (p < 0.01). In the overall sample of obese men, visceral AT accumulation (but not the fat mass) was positively correlated with plasma insulin (r = 0.70) and glucagon responses (r = 0.63) to the hormone infusion (p < 0.01). These metabolic responses were not related to the achieved catecholamine concentration. CONCLUSION: These results suggest that some of the impairments in plasma glucose-insulin homeostasis noted in visceral obesity may be related to an abnormal metabolic response to an adrenaline challenge.

Abdomen↗
PubMed1996

Associations between 12 year changes in body fatness and lipoprotein-lipid levels in men and women of the Québec Family Study.

OBJECTIVE: To investigate the associations between 12 year changes in body composition, subcutaneous fat distribution vs changes in plasma lipoprotein-lipid levels. DESIGN: 12 year prospective study. SUBJECTS: A sample of 95 women and 93 men of the Québec Family Study initially tested in 1980. MEASUREMENTS: Various body fatness variables as well as fasting plasma lipoprotein-lipid concentrations performed both in 1980 and 1992. RESULTS: In both 1980 and 1992, a high body fat mass and an elevated accumulation of subcutaneous trunk fat were associated with a significant deterioration in the plasma lipoprotein-lipid profile. Furthermore, correlation analysis performed on differences noted during the 12 years follow-up revealed significant associations between changes in body fat mass and in plasma cholesterol [r = 0.52, P < 0.0005] in women. In both men and women, an increased body fat mass was associated with an increased CHOL/HDL-cholesterol ratio [r = 0.37, P < 0.01 (men) and r = 0.54, P < 0.0005 (women)]. Correlations between changes in fat mass and plasma lipids were generally of higher magnitude in women than in men. Changes in subcutaneous trunk fat were associated with changes in plasma HDL-chol levels (r = -0.22, P < 0.05) in men whereas in women, changes in trunk adiposity were related to changes in both plasma CHOL (r = 0.25, P < 0.05) and TG (r = 0.32, P < 0.005) levels. CONCLUSION: These results support the notion that the increased adiposity observed among aging adult men and women is a significant component of the deterioration in the plasma lipoprotein-lipid profile noted over a 12 year follow-up period.

Adipose Tissue↗
PubMed1995

Do elevated levels of abdominal visceral adipose tissue contribute to age-related differences in plasma lipoprotein concentrations in men?

Age-related differences in body fat and more specifically in the accumulation of abdominal visceral adipose tissue were examined as a potential covariate for the alteration in the plasma lipoprotein profile found with aging. For that purpose, results from 79 young adults (aged 24.5 +/- 4.0 years) were compared to 61 middle-aged men (54.7 +/- 6.4 years). Younger men had significantly lower body fat mass and abdominal visceral adipose tissue area measured by computed tomography than middle-aged men (P < 0.0001). Plasma cholesterol, triglyceride, apolipoprotein (apo) B, low density lipoprotein (LDL)-cholesterol and LDL apo B levels, as well as the ratio of plasma cholesterol to high density lipoprotein (HDL)-cholesterol were all significantly lower in younger men as compared to middle-aged men (P < 0.0001). The comparison of younger men to middle-aged men with comparable levels of abdominal visceral fat and total body fat eliminated the age-related differences in plasma triglyceride and in the ratio of plasma cholesterol to HDL-cholesterol, whereas the difference in plasma apolipoprotein B levels, although still significant, was largely reduced. Age-related differences in plasma cholesterol and in LDL-cholesterol levels were still observed after this matching procedure and the differences between age-groups were essentially of similar magnitude than before pairing. In summary, these results suggest that the deterioration of plasma lipoprotein profile observed in middle-aged men as compared to young adult men is partly mediated by concomitant increases in total body fat and abdominal visceral adipose tissue. However, other factors related to the aging process appear to be involved, particularly for the age-related increase in plasma LDL-cholesterol.

Adipose Tissue↗
PubMed1995

Plasma glucose, insulin, and glucagon before and after long-term overfeeding in identical twins.

Plasma glucose, insulin, and glucagon levels were measured before and after long-term overfeeding (4.2 MJ/d during a 100-day period) in 24 lean adults (12 pairs of monozygotic twins). Fasting plasma glucose, insulin, and glucagon were significantly increased by overfeeding. During a 75-g oral glucose tolerance test (OGTT), no major alteration in glucose tolerance was observed and insulin area under the curve was increased. During a meal test, insulin and glucagon areas under the curve were increased. The pre-overfeeding values for glucose, insulin, and glucagon (fasting and areas) were not correlated with the gains in body weight and in fat mass. However, fasting glucagon before overfeeding was positively correlated with the gains in abdominal visceral fat and in femoral fat. The changes with overfeeding in insulin area during the OGTT were positively correlated with the changes in total subcutaneous fat, even after adjustment for total body fat gain. Significant twin intrapair similarity was observed for fasting plasma glucagon before overfeeding and for the changes in fasting insulin and glucagon with overfeeding. These results indicate that (1) in response to long-term overfeeding, both fasting insulin and glucagon are increased; (2) initial levels of glucose, insulin, and glucagon do not predict the gains in body weight and total body fat during overfeeding, but are related to changes in indicators of fat topography; (3) the changes in total subcutaneous fat represent an important correlate of insulin changes with overfeeding; and (4) the genotype could be an important determinant of insulin and glucagon responses to a prolonged positive-energy-balance period.

Adipose Tissue↗
PubMed1995

Exercise and energy intake: effect of substrate oxidation.

The main objective of this study was to evaluate the short-term effect of exercise-induced alteration in fat oxidation on postexercise spontaneous energy and macronutrient intakes. Eleven young males were submitted to two randomly assigned sessions of 48 h each, during which they were requested to eat in the laboratory. One of these sessions was preceded by a 90-min exercise bout at an intensity of 60% VO2max. During both sessions, subjects ate ad lib food with a fat content conforming to the recommendations of nutrition agencies with a food quotient (FQ) > or = 0.85. Results showed that there was no significant change in postexercise energy and macronutrient intakes in comparison with the sedentary session. However, when subjects were subdivided into two groups on the basis of the respiratory quotient (RQ) measured during exercise, men with a low RQ (high fat oxidation) were characterized by a reduced postexercise increase in energy intake relative to the energy cost of exercise (ECE), i.e., they were more predisposed to be in negative postexercise energy balance compared to those exhibiting a high RQ. Accordingly, exercise RQ was positively associated with postexercise energy and lipid balance. These results show that postexercise energy balance partly depends on the composition of the substrate mix oxidized during exercise.

Adult↗
PubMed1995

Hyperinsulinemia and regulation of energy balance.

Recent data suggest that hyperinsulinemia with euglycemia may favor the restoration of energy balance when one gains body weight. To test the validity of this concept in humans, the data of 24 young men who had been exposed to a 353-MJ overfeeding protocol for 100 d and who were remeasured after a 4-mo follow-up were analyzed. The sample was subdivided in two groups on the basis of the overfeeding-induced change in postprandial plasma insulin. The increase in postprandial energy expenditure induced by overfeeding was significantly greater in high than in low postprandial insulin responders (P < 0.05) but not after body fat gain was controlled for. After the overfeeding protocol, the loss of subcutaneous adiposity was greater in high than in low postprandial insulin responders. However, this difference was no more significant after the gain in fat mass was controlled for. There was no difference between the two groups in post-overfeeding loss of body weight, fat mass, or fat-free mass. These results partly agree with the idea that hyperinsulinemia resulting from a long-term positive energy balance and its associated fat gain exert a regulatory role promoting the restoration of energy balance.

Adipose Tissue↗
PubMed1995

Alcohol and a high-fat diet: a combination favoring overfeeding.

The effects of alcohol and dietary fat on spontaneous energy and macronutrient intakes were investigated in eight male subjects who participated in a protocol including four randomly assigned 2-d sessions during which they ate ad libitum. In each session they had free access to either high- or low-fat foods, with alcohol or a placebo. The high-fat diet was associated with a substantial increase in daily energy intake. Alcohol had no inhibitory effect on food intake and its energy content was thus associated with an additional increase in energy intake. The enhancing effects of alcohol and dietary fat on daily energy intake were additive so that overfeeding was maximal (2.8 MJ/d) under the high-fat diet+alcohol condition. To further examine the effects of alcohol on energy and macronutrient intakes, reported food intake was studied in 351 men and 360 women who had been tested in the Québec Family Study. The results showed that a high alcohol intake was associated with a high daily energy intake and had no inhibitory effect on lipid intake. In conclusion, a dietary regimen providing a high fraction of energy as alcohol and fat increases the risk for positive energy balance under free-living conditions.

Adult↗
PubMed1995

Sleep and psychological characteristics of children on a psychiatric inpatient unit.

OBJECTIVE: To assess the association of objective measures of sleep-wake patterns and psychological status and abuse history of children hospitalized in a psychiatric inpatient unit. METHOD: Thirty-nine inpatient children participated in the study. They were monitored for one to three consecutive nights with miniature wrist activity monitors for objective assessment of sleep-wake patterns. In addition, a thorough psychiatric and psychosocial assessment was completed with each child and the parents. RESULTS: Children's self-ratings of depression, hopelessness, and low self-esteem were significantly correlated with objective sleep measures indicating poorer sleep quality. No significant correlations between intelligence scores and sleep measures were found. Nonabused and sexually abused children had better sleep quality than physically abused children. CONCLUSIONS: Sleep quality during hospitalization is strongly associated with self experiences of depression, hopelessness, and low self-esteem in children with severe behavior disorders.

Adolescent↗
PubMed1995

Regional differences in adipose tissue lipolysis from lean and obese women: existence of postreceptor alterations.

Lipolysis studies were performed on isolated adipose cells obtained from two subcutaneous regions (abdominal and femoral) in 26 premenopausal women (16 obese and 10 lean subjects). Because obese adipocytes from both sites were significantly larger than lean fat cells, glycerol release measured by an ultrasensitive bioluminescent method was corrected for variation in cell surface area. Epinephrine induced antilipolysis at low concentrations and a net lipolytic response at higher doses, regardless of the subjects' fatness and the anatomic location of fat. However, the catecholamine and the selective alpha 2-adrenergic agonist, UK-14304, promoted a greater maximal antilipolytic response in both femoral and subcutaneous abdominal adipose cells from obese individuals that from lean individuals. Epinephrine- and UK-14304-induced maximal antilipolysis of femoral adipocytes was also positively associated with indicators of total adiposity. On the other hand, the maximal lipolytic responses to postadrenoceptor agents such as dibutyryl adenosine 3',5'-cyclic monophosphate, forskolin, and theophylline were lower in both adipose regions in obese than in lean women. Femoral fat cell lipolysis in the presence of these agents was negatively correlated with body fatness indexes. These results suggest that, in women covering a wide range of adiposity, variations in the lipolytic response of femoral fat cells to epinephrine may involve changes in the functional balance between alpha 2- and beta-adrenoceptors and also alterations located at different postreceptor levels.

Abdomen↗