Fasted state training burns fat, spares glycogen, new study shows.
Old news, new study.
http://www.ncbi.nlm.nih.gov/pubmed/23313101Effects of post-absorptive and postprandial exercise on 24h fat oxidation.SourceDoctoral Program in Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, Japan 305-8574.
AbstractOBJECTIVE:Fat oxidation during exercise depends on nutritional state, and exercise performed in the post-absorptive state oxidizes more fat than that performed in the postprandial state. However, the effects of exercise on energy metabolism continue during the post-exercise period, and the difference in fat oxidation during exercise may be compensated for during the post-exercise period. The present study compared the effects of an acute exercise bout in the post-absorptive or postprandial state on 24h fat oxidation.
METHODS:Twelve young male athletes stayed twice in a room-size metabolic chamber for 24h indirect calorimetry in a randomized repeated-measure design. Before or after breakfast, i.e. in the post-absorptive or postprandial state, subjects exercised at 50% VO(2) max for 60min.
RESULTS:During the 60min of exercise, energy expenditure in the two exercise trials were equivalent, but exercise in the post-absorptive state was performed with lower RQ compared with that in the postprandial state (P<0.01). The time of exercise relative to breakfast did not affect 24h energy expenditure (P>0.5). However, accumulated 24h fat oxidation was higher (P<0.05) and that of carbohydrate oxidation was lower (P<0.05) when exercise was performed in the post-absorptive state.
CONCLUSIONS:Compared with exercise performed in the postprandial state, exercise performed in the post-absorptive state oxidized more fat and saved more carbohydrate in the body, without affecting 24h energy expenditure.