Medical Library

Pediatric exercise physiology symposium: a tribute to Oded Bar-Or.

Dr. Oded Bar-Or was a pioneer in the study of children\’s physical activity, exercise, and health. His diverse research interests led to numerous scientific explorations on thermoregulation, aerobic and anaerobic capacity, physical activity, economy of movement, obesity, neuromuscular diseases, asthma, cystic fibrosis (CF), and many more. To commemorate the extraordinary contributions that Dr. Bar-Or made to the study of exercise and youth, a symposium on pediatric exercise physiology was held at the CSEP\’s 2006 Annual Meeting in Halifax. The papers in the following pages include the four papers presented by international colleagues in his memory.

Klentrou PN.

International conference on physical activity and obesity in children: summary statement and recommendations.

The increasing prevalence of obesity among the world\’s children and youth was the impetus for an international conference convened in Toronto, Canada, to examine issues related to physical activity and obesity in children (24-27 June 2007). The goal of the conference was to assimilate, interpret, and share scientific evidence with key stakeholders to develop recommendations concerning effective physical activity policies and programs to address obesity in children. The conference was attended by approximately 1000 delegates from 33 countries who gathered to listen to the invited speakers and to share information on promising practices related to the promotion of physical activity with the aim of reducing the burden of obesity in children. The major topics addressed at the conference included the biological and behavioural causes of obesity, current and past levels of physical activity and sedentarism in children, the role of the social, family, and built environments in addressing the physical activity deficit, and the role of legislation and industry in promoting physical activity. Promising physical activity interventions among children were presented, and important research, policy, and practice recommendations to address the issue of physical inactivity and obesity were provided.

Katzmarzyk PT, Baur LA, Blair SN, Lambert EV, Oppert JM, Riddoch C.

Pennington Biomedical Research Center, Louisianna State University System, 6400 Perkins Road, Baton Rouge, LA 70808, USA.

Book reviews / Critiques des livres.

Shephard RJ.

Role of physiology and environmental factors on food intake control in boys.

To examine the hypothesis that physiologic regulation of short-term food intake (FI) in boys is affected by the interaction between physiological and environmental factors, four studies were conducted. The primary objectives were as follows: (i) to compare the effect of glucose and whey-protein (50 g) preloads on satiety and FI as affected by time to the next meal and body composition in normal weight (NW) and obese (OB) boys; (ii) to examine the role of short-duration physical activity on subjective appetite and to identify the role of and associations between fitness and FI at a pizza lunch 30 min after glucose and whey-protein drinks in NW boys; (iii) to determine the effect of television viewing (TVV) on FI of boys at a meal and its effect on caloric compensation at the test meal after a premeal glucose drink; and (iv) to determine the reproducibility of short-term FI and subjective appetite after a glucose preload, ventilation threshold (VT), and body composition assessed by bioelectrical impedance analysis (BIA). Obese boys responded less than NW boys to whey protein, with time (30 vs. 60 min) to the next meal the response decreasing to glucose but increasing to protein. Subjective appetite was increased by short-duration physical activity and FI following glucose and whey-protein preloads was positively associated with VT in boys. TVV while eating a meal contributed to increased energy intake by delaying normal mealtime satiation and reducing satiety signals from previously consumed foods. Short-term FI after a glucose preload, subjective appetite after glucose and physical activity, VT, and body composition assessed by BIA were reproducible in boys. In conclusion, physiologic regulation of short-term FI in boys was affected by the interaction between physiological and environmental factors. Macronutrient source, body weight and composition, time to the next meal, short-duration physical activity and fitness, and TVV at mealtime impacted on FI regulation in boys.

Bellissimo N.

Metabolic syndrome in three ethnic groups using current definitions.

According to two current definitions, the prevalence of the metabolic syndrome (MetS) aamong black Haitians of Montreal was <20%, 30%-36% in Algonquin Indians of Quebec, and >45% in Mexicans of Oaxaca (all aged 35-60 y). Although phenotypes were different, high triglycerides and fasting dysglycemia were good predictors of MetS in all three groups using both definitions. The international cut-offs for abdominal obesity were not predictive of MetS in the Haitian subjects.

Delisle H, Désilets MC, Vargas ER, Garrel D.

Correlation between the rate of weight loss and changes in body composition in obese postmenopausal women after 5 weeks: a pilot study.

Approximately 25% of weight lost during restrictive diets (without exercise) is lean body mass (LBM). No study has yet investigated the impact of the rate of weight loss (RWL) on LBM and fat mass (FM). The purpose of this study was to investigate the relationships between the RWL and body composition in older obese women. Twenty obese postmenopausal women aged between 51 and 74 years enrolled in a 5 week dietary weight loss intervention. Subjects were characterized according to their RWL (low RWL < 0.74 kg.week-1 (n = 9) vs. high RWL >= 0.74 kg.week-1 (n = 11)). Total and trunk FM and LBM (by dual-energy X-ray absorptiometry) were measured before and after weight loss. A significant correlation was observed between the RWL (kg.week-1) and changes in LBM (kg.week-1) (r = 0.75; p = 0.0002). However, no association was observed with changes in FM (kg.week-1) (r = 0.40; p = 0.08). Both groups showed a similar decrease in FM (low RWL, -2.7 +/- 0.9 kg,; high RWL, -3.2 +/- 0.8 kg; p = 0.38), whereas losses in LBM were significantly higher in the high RWL than in the low RWL group (-1.6 +/- 1.2 kg vs. -0.4 +/- 1.1 kg; p = 0.05). An RWL > 0.74 kg.week-1 was associated with a greater loss of LBM, but had no extra benefits on FM after a 5 week weight loss program. Current guidelines, which recommend RWL up to 0.91 kg.week-1, might not be optimal to prevent decreases in LBM in postmenopausal women when no exercise is added.

Arguin H, Bouchard DR, Labonté M, Carpentier A, Ardilouze JL, Dionne IJ, Brochu M.

Parents report intrapersonal, interpersonal, and environmental barriers to supporting healthy eating and physical activity among their preschoolers.

There is an increasing trend in childhood obesity in Canada and many preschool children are overweight or obese. The objective of this study was to explore parents\’ experiences and challenges in supporting healthy eating and physical activity among their preschool children. A qualitative descriptive study involving 5 focus groups was conducted. A convenience sample of 39 parents from 3 childcare centres in Hamilton, Ontario, participated. Parents were English speaking and had a child aged 2-5 years attending the childcare centre for at least 3 months. The research team read transcripts of the audio-taped sessions and used a constant comparison approach to develop themes, which involved coding comments by continually referring to previously coded comments for comparison. The social ecological model was used to organize the themes into 3 higher-level categories: (i) intrapersonal (individual): preschoolers\’ preferences and health; (ii) interpersonal (interactions): parents\’ and others\’ different views and practices, influence of the childcare centre, parents\’ lack of time, and family structure; and (iii) physical environment: accessibility of healthy foods, preschoolers with special needs, media influence, weather, lack of safety, and inaccessible resources. Parents perceived that there are various intrapersonal, interpersonal, and environmental barriers to supporting healthy eating and physical activity among their children. Program planners and health professionals can consider these barriers when developing interventions to promote healthy bodyweights among preschoolers.

Dwyer J, Needham L, Simpson JR, Heeney ES.

Reproducibility of short-term food intake and subjective appetite scores after a glucose preload, ventilation threshold, and body composition in boys.

The objective of these studies was to assess the reproducibility of (i) short-term food intake (FI) and subjective appetite following a glucose preload, (ii) ventilation threshold (VT) and subjective appetite after short-duration exercise, and (iii) body composition assessed by bioelectrical impedance (BIA). On two separate weekend mornings, boys (n = 11; aged 9-14 years) received drinks containing 50 g glucose made up to 250 mL with water 2 h after a standardized breakfast. FI from a pizza meal was measured 30 min later. Subjective appetite was measured before and after the glucose loads and the VT measures. VTs were measured on 2 weekday evenings, 1 week apart. BIA was measured during the FI assessment sessions. Short-term FI after the glucose preload was highly reproducible. Mean energy intake was 925 +/- 139 kcal on the first day and 988 +/- 147 kcal on the second day (coefficient of repeatability (CR) = 259 kcal; intra-class correlation coefficient (ICC) = 0.96). Moderate reproducibility of the average appetite score was found at 30 min (CR = 24 mm; ICC = 0.82). Subjective appetite was increased similarly by short-duration exercise on both days (CR = 19 mm). Absolute VT was more highly reproducible (CR = 359 mL O2.min-1, ICC = 0.85) than VT expressed on the basis of body weight (CR = 8.0 mL O2.kg-1.min-1, ICC = 0.59). Fat mass (FM) estimated from BIA was highly reproducible (CR = 2.7 kg, ICC = 0.95), but underestimated FM compared with skinfolds. In conclusion, FI and subjective appetite scores in response to glucose preloads, VT, subjective appetite after short-duration exercise, and estimates of FM from BIA are reproducible in boys.

Bellissimo N, Thomas SG, Pencharz PB, Goode RC, Anderson GH.

Adding carbohydrate to a high-fat meal blunts postprandial lipemia in women and reduces meal-derived fatty acids in systemic circulation.

The lipemic response to a meal is an important independent risk factor for the development of cardiovascular disease. The purpose of this study was to determine the effect of adding carbohydrate (CHO) to a fat meal on the bioavailability of ingested fat in different blood lipid fractions in men and women. On two separate occasions, 18 healthy adults (9 women, 9 men) ate either a high-fat meal (0.7 grams fat per kilogram) (FAT), or the same meal with added CHO (1 gram CHO per kilogram) (FAT+CHO) in the morning after a 12 h fast. Both meals were supplemented with [13C]-palmitate (25 mg.kg-1). Plasma concentrations of triglyceride (TG), fatty acids, insulin, and glucose were measured in blood samples taken hourly from 0 to 8 h after the meal. In addition, we measured TG concentrations in chylomicron (CHYLO-TG) and in very-low-density lipoprotein (VLDL-TG) fractions. The addition of CHO to the fat meal increased plasma glucose and insulin concentrations identically in men and women. In contrast, adding CHO to the fat meal reduced the plasma TG concentration in the 5 h after the meal in women (average 5 h [TG]: 1.27 +/- 0.11 and 1.01 +/- 0.09 mmol.L-1; p <0.05), but not in men (1.25 +/- 0.23 and 1.24 +/- 0.20 mmol.L-1). Despite differences in the lipemic response to the meals between men and women, we found that adding carbohydrate to a fat meal decreased the bioavailability of meal-derived [13C]-palmitate in the systemic fatty acid pool, and decreased the incorporation of [13C]-palmitate into VLDL-TG in both men and women. In summary, adding CHO to a fat meal markedly blunted the plasma TG response in women, but not in men, which may augment the atherogenic potential after each meal in men.

Knuth ND, Remias DB, Horowitz JF.

Substrate Metabolism Laboratory, Division of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109-2214.

Relationship between the metabolic syndrome and physical activity energy expenditure: a MONET study.

The purpose of this cross-sectional study was to examine the association between the metabolic syndrome (MetS) and physical activity energy expenditure (PAEE) in overweight and obese sedentary postmenopausal women. The study population consisted of 137 overweight and obese sedentary postmenopausal women (age, 57.7 +/- 4.8 years; BMI, 32.4 +/- 4.6 kg.m-2). Subjects had the MetS if 3 out of the following 5 criteria were met: visceral fat > 130 cm2, high-density lipoprotein (HDL) cholesterol < 1.29 mmol.L-1, fasting triglycerides >= 1.7 mmol.L-1, blood pressure >= 130/85 mmHg, and fasting glucose >=5.6 mmol.L-1. We measured (i) body composition (by dual-energy X-ray absorptiometry); (ii) visceral fat (by computed tomography); (iii) insulin sensitivity (using the hyperinsulinemic-euglycemic clamp); (iv) plasma lipids, fasting glucose, and insulin, as well as 2 h glucose during an oral glucose tolerance test; (v) resting blood pressure; (vi) peak oxygen consumption (VO2 peak); (vii) PAEE (using doubly labeled water); and (viii) lower-body muscle strength (using weight-training equipment). Forty-two women (30.7%) had the MetS in our cohort. Individuals without the MetS had significantly higher levels of PAEE (962 +/- 296 vs. 837 +/- 271 kcal.d-1; p < 0.05), VO2 peak (18.2 +/- 3.0 vs. 16.7 +/- 3.2 mL.min-1.kg-1; p < 0.05), and insulin sensitivity, as well as significantly lower levels of 2 h glucose and central lean body mass. No differences in total energy expenditure, resting metabolic rate, and muscle strength between groups were observed. Logistic regression analysis showed that 2 h glucose (odds ratio (OR): 1.50 (95% CI 1.17-1.92)), central lean body mass (OR: 1.17 (95% CI 1.05-1.31)), and PAEE (OR: 0.998 (95% CI 0.997-1.000)), but not VO2 peak and (or) muscle strength, were independent predictors of the MetS. Lower levels of PAEE and higher levels of 2 h glucose, as well as central lean body mass, are independent determinants of the MetS in our cohort of overweight and obese postmenopausal women.

Karelis AD, Lavoie ME, Messier V, Mignault D, Garrel D, Prud\’homme D, Rabasa-Lhoret R.