Objectives: A randomized crossover trial was designed to analyze the impact of a short-term, isoenergetic fat-rich or carbohydrate (CHO)-rich diet on substrate oxidation rates during submaximal exercise and on performance in a 10,000-m running time trial in trained, mid- to late-pubertal boys.
Methods: An incremental test was performed to determine the peak oxygen uptake (VO2peak). After 2 days on a fat-rich (24.2% ± 0.8% CHO, 60.4% ± 0.3% fat, and 15.5% ± 1.0% protein), CHO-rich (69.3% ± 1.2% CHO, 15.9% ± 2.1% fat, and 15.1% ± 1.1% protein), or habitual (56.1% ± 7.0% CHO, 27.5% ± 4.9% fat, and 16.5% ± 4.0% protein) diet, 19 trained adolescent boys (15.2 ± 1.5 years) performed a 10-minute constant run at 65% VO2peak to determine the respiratory exchange ratio (RER) during exercise and 10,000-m running on an outdoor track.
Results: During the constant run, the RER and CHO contribution to energy expenditure were lower, and fat contribution higher, in the fat-rich diet than in the CHO-rich diet (P < 0.05), but the results were not different from those of the habitual diet. Performance in the 10,000-m run after consuming CHO- and fat-rich diets was similar to performance after a habitual diet (50.0 ± 7.0, 51.9 ± 8.3, and 50.9 ± 7.4 minutes, respectively), but consuming a CHO-rich diet enhanced performance compared with that after a fat-rich diet (P = 0.03).
Conclusions: These findings indicate that a CHO-rich diet provides additional benefits to 10,000-m running performance in trained adolescent boys compared with a fat-rich diet.
*Endurance Performance Research Group, School of Physical Education and Sport, University of São Paulo, São Paulo
†Sport Science Research Group, Department of Physical Education and Sports Science (CAV), Federal University of Pernambuco and Federal University of Alagoas, Alagoas
‡Human Movement Studies Group, Physical Education Department, Federal University of Lavras, Lavras, Brazil.
Address correspondence and reprint requests to Patricia Guimaraes Couto, Endurance Performance Research Group, School of Physical Education and Sport, University of São Paulo, Prof Mello de Morais Ave, 65, São Paulo 05508-030, Brazil (e-mail: firstname.lastname@example.org).
Received 10 January, 2014
Accepted 30 April, 2014
The authors report no conflicts of interest.