Severely obese adolescent girls rely earlier on carbohydrates during walking than normal-weight matched girls (original) (raw)
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Six-minute walking test predicts maximal fat oxidation in obese children
International journal of obesity (2005), 2012
Obesity is associated with reduced exercise maximal fat oxidation rate (FATmax), which is generally assessed by cardiopulmonary cycling test. The six-minute walking test (6MWT) presents an alternative method in patients. The aim of this study was to establish a practical reference equation facilitating the prediction of FATmax from the 6 MWT in obese children of both genders. This study is a cross-sectional study using mixed linear and multiple regression models. Anthropometric measurements were recorded and submaximal cycling test and 6 MWT conducted for 131 school-aged obese children, 68 boys and 63 girls. A multiple regression analysis for FATmax, including six-minute walking distance (6 MWD), anthropometric and cardiac parameters as the dependent variables, was performed for the two genders separately. Mean 6 MWD and FATmax were 564.9 ± 53.7 m and 126.5 ± 12.1 mg min(-1) for boys and 506.7 ± 55.0 m and 120.7 ± 10.0 mg min(-1) for girls, respectively. The 6MWD, body mass index, Z...
Nutrient Oxidation during Moderately Intense Exercise in Obese Prepubertal Boys
The Journal of Clinical Endocrinology & Metabolism, 2005
The aim of this study was to measure the nutrient oxidation rate during walking at different speeds and to identify the walking speed associated with the highest fat oxidation rate in a group of prepubertal boys with different levels of adiposity. Twenty-four prepubertal boys (age, 10 ± 1 yr) with different levels of overweight (body mass index, 25.5 ± 3.5 kg/m2; sd score of body mass index, 3.4 ± 1.1) performed a treadmill test. We measured by indirect calorimetry their respiratory exchange while they walked at speeds of 4, 5, and 6 km/h as well as their maximal oxygen uptake. The fat oxidation rate did not change significantly when the speed of walking was increased, whereas carbohydrate oxidation increased significantly (P < 0.001). A significant (P < 0.05) association was found between adiposity (percent fat mass) and the fat to carbohydrate oxidation ratio during walking at 4, 5, and 6 km/h (r = 0.37, r = 0.37, and r = 0.36, respectively), adjusting for exercise intensity...
Optimizing fat oxidation through exercise in severely obese Caucasian adolescents
Clinical Endocrinology, 2007
Objective To measure the contribution of substrate oxidation to energy expenditure during cycling at different workloads and to identify the exercise intensity that elicits the maximum fat oxidation rate in groups of severely obese or nonobese Caucasian adolescents. Design A total of 30 severely obese subjects (mean body mass index, BMI = 34·7 kg/m 2 ; fat-mass = 39·9%) and 30 nonobese sedentary adolescents (mean BMI = 22·7 kg/m 2 ; fat-mass = 21·8%) aged 14-16 years, participated in this study. Body composition was assessed by bioelectrical impedance. Peak oxygen uptake ( V O 2 peak) and maximal fat oxidation rate were determined with indirect calorimetry by using a graded exercise test on an electromagnetically braked cycle ergometer. Results Predicted V O 2 max were expressed in absolute (l /min) and relative (ml / kg FFM / min) values, and maximal work rates were not significantly different between obese and nonobese adolescents, but were significantly higher in boys than in girls. No significant differences in fat oxidation rates were found in obese and nonobese sedentary adolescents during the graded exercise test. Maximal fat oxidation was observed at an exercise intensity corresponding to (mean ± SD) 41 ± 3% V O 2 max or 58 ± 3% HR max . At this exercise intensity, fat oxidation rates were higher in boys than in girls (0·32 ± 0·02 g/min vs. 0·25 ± 0·02 g/min, P < 0·001). Conclusions Severely obese and sedentary nonobese adolescents reached maximal fat oxidation rates at 41% V O 2 max, which corresponds to 58% HR max . At this exercise intensity, fat oxidation rates were higher in boys than in girls probably due to higher V O 2 max and absolute workload during the exercise steps for boys compared with those for girls.
Revista internacional de ciencias del deporte, 2010
INTRODUCTION: Maximal oxygen uptake (VO2 max) is associated with cardiovascular and metabolic risks but it is difficult to assess in obese children. The objective of this study was to develop an equation to estimate VO2 (mL/kg/min) and to check the % of tests that were maximal according to recommended criteria. METHODS: Stress tests were analyzed of 222 subjects (94 male and 128 female with a BMI above the 85 percentile for age and sex), and repeated 4 months later. Mean age was 9.4 ± 1.1 years and weighed 52.4 ± 13.3 kg. Body fat % (40.5 + 6.2) was determined by DXA (Hologic QDR 4500W). The protocol on the treadmill started with a warm up at 2.5 and 3 mph with a slope of 0% and 2%. The speed was kept at 3 mph for all the stages and the slope was increased 2% every 2 minutes. Statistical analysis (descriptive, t-test and ANOVAS 2×2×2) was done with SPSS 15.0. RESULTS: Only 35% of the tests were maximal. The equation calculates was Y = 2.6x + 22.3 (x = protocol stage). Data pre and p...
Assessment of Oxygen Deficit during Exercise in Obese Children and Adolescents
Pediatric Exercise Science
This study analyzes whether cardiorespiratory exercise performance is impaired in obese children when parameters of aerobic exercise function are used that are independent of body mass. Twenty-one obese patients (mean age 11.6 ± 2.5 years) were studied and compared with 22 normal controls of the same age range (11.4 ± 2.2 years; p = .78). All participants underwent square wave exercise testing on a treadmill for 6 min (speed 5 km/hr, inclination 4%). The oxygen deficit, calculated as ml·min·kg−1, was expressed as a percentage of the total oxygen cost for the 6-min exercise bout (also expressed as ml·min·kg−1). Oxygen deficit amounted to 7.2 ± 1.9% in the obese patients and was not significantly different (p = .25) from the normal controls (6.6 ± 1.1%). The similar values for O2 deficit in obese patients compared with normal controls shows that cardiovascular fitness in obese patients is normal when parameters of aerobic exercise function are not normalized per kg of body mass.
Clinical Nutrition, 2011
Background & aims: Exercise induces adaptations in fat metabolism favourable to the treatment of obesity. However, time interval between meal and exercise alters substrate bioavailability and oxidation during exercise. The aim of this study was therefore to investigate the effect of time interval between food intake and exercise on substrate oxidation rates in obese and lean children. Methods: The metabolic responses to exercise of nine obese children (10.3 AE 1.8 years; %body fat: 36.1 AE 6.1) and seven lean children (9.2 AE 1.6 years; %body fat: 22.2 AE 4.1) were compared 1 h (time interval 1, TI1) and 3 h (TI3) after a standardized breakfast. Results: Despite significantly lower plasma glucose and insulin concentrations and large effect size suggesting a higher plasma FFA availability (lean, 1.43, obese 0.98), fat oxidation was not significantly increased in TI3 compared to TI1 in both lean and obese children. Fat oxidation contributed marginally to energy expenditure during exercise (<20%) in both conditions and groups but was moderately increased during TI3 compared to TI1 in lean children (effect size: 0.54). Conclusions: The low contribution of fat oxidation to energy expenditure during exercise in obese and lean children fed 3 h before exercise questions the efficacy of moderate intensity exercise to favourably affect fat balance.
Increased lipid oxidation during exercise in obese pubertal girls: A QUALITY study
Obesity, 2013
This study explores differences in LO rates between pre-pubertal and pubertal girls of three body weight status groups. Methods: The sample included 39 pre-pubertal girls [12 normal-weight (NW), 12 overweight (OW), and 15 obese (OB)] and 37 pubertal girls [16 NW, 10 OW, and 11 OB]. Following a rest period, the girls performed a graded maximal cycling test. The %LO contribution was computed at each stage. Results: The %LO contribution did not differ between NW, OW, or OB pre-pubertal girls at each exercise stage. In contrast, pubertal OB girls showed a statistically significantly higher %LO contribution at 25, 50, and 75 W stages compared with OW and NW as well as with OB pre-pubertal girls. Conclusions: Our results demonstrate that entering puberty is a period associated with differentiation in substrate selection in obese girls. A higher %LO contribution may help girls to solicit more fat while performing submaximal exercise.
Oxygen Uptakes Adjusted for Body Composition in Normal-Weight and Obese Adolescents**
Obesity, 2004
Objective: To test whether resting oxygen uptake (VO 2), submaximal VO 2 , and maximal VO 2 (VO 2max) differs between obese adolescents (n ϭ 18; BMI Ͼ 30) and a matched normal-weight control group after adjustment for differences in fat-free mass (FFM) and fat mass (FM). Research Methods and Procedures: FFM and FM were assessed by DXA. Resting VO 2 , submaximal VO 2 , and VO 2max were measured by indirect calorimetry. Results: There was no difference in resting VO 2 between groups after adjusting for FFM and FM. Submaximal VO 2 did not differ between groups after adjusting for body weight. Percentage VO 2max and NET VO 2 (VO 2max Ϫ resting VO 2) were significantly higher in the obese group during submaximal exercise, however not after adjusting for body weight. VO 2max was not significantly different between groups after adjusting for FFM. Discussion: When body compositions are appropriately controlled for, resting VO 2 , submaximal VO 2 , and VO 2max do not differ between obese and normal-weight adolescents. These data suggested that the higher relative VO 2 observed in obese adolescent subjects is due to their higher FM and not to an impaired VO 2max even though they may be less physically active.