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Optimizing fat oxidation through exercise in severely obese Caucasian adolescents
Author(s) -
Lazzer Stefano,
Busti Carlo,
Agosti Fiorenza,
De Col Alessandra,
Pozzo Renzo,
Sartorio Alessandro
Publication year - 2007
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.2007.02929.x
Subject(s) - bioelectrical impedance analysis , medicine , endocrinology , body mass index , exercise intensity , cycle ergometer , obesity , vo2 max , lipid oxidation , exercise physiology , fat mass , cycling , chemistry , zoology , heart rate , blood pressure , biology , antioxidant , biochemistry , archaeology , history
Summary 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 (V̇O 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 V̇O 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%V̇O 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%V̇O 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 V̇O 2 max and absolute workload during the exercise steps for boys compared with those for girls.