Exercise and Fat Metabolism

Comment - this is another study that shows that there are benefits to intervals in terms of improving the body's burning of fat. It is a bit odd in that we normally think of intervals as short sprints....here we are talking about two 30 minutes pieces at moderate intensity rather than one single 60 minute session. I would like to have had them test other intervals as well to see if the benefits were increased as the intervals got shorter and more intense. Anyway there is perhaps another conclusion that as the session gets longer fat metabolism tails off......The study is also commented on here

Enhancement of fat metabolism by repeated bouts of moderate endurance exercise
Kazushige Goto,1,2 Naokata Ishii,1 Ayuko Mizuno,3 and Kaoru Takamatsu3

1Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Tokyo, Japan; 2Institute of Sports Medicine, Bispebjerg Hospital, Copenhagen, Denmark; and 3Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan

Submitted 17 November 2006 ; accepted in final form 19 February 2007


This study compared the fat metabolism between "a single bout of prolonged exercise" and "repeated bouts of exercise" of equivalent exercise intensity and total exercise duration. Seven men performed three trials: 1) a single bout of 60-min exercise (Single); 2) two bouts of 30-min exercise, separated by a 20-min rest between exercise bouts (Repeated); and 3) rest. Each exercise was performed with a cycle ergometer at 60% of maximal oxygen uptake. In the Single and Repeated trials, serum glycerol, growth hormone, plasma epinephrine, and norepinephrine concentrations increased significantly (P < 0.05) during the first 30-min exercise bout. In the Repeated trial, serum free fatty acids (FFA), acetoacetate, and 3-hydroxybutyrate concentrations showed rapid increases (P < 0.05) during a subsequent 20-min rest period. During the second 30-min exercise bout, FFA and epinephrine responses were significantly greater in the Repeated trial than in the Single trial (P < 0.05). Moreover, the Repeated trial showed significantly lower values of insulin and glucose than the Single trial. During the 60-min recovery period after the exercise, FFA, glycerol, and 3-hydroxybutyrate concentrations were significantly higher in the Repeated trial than in the Single trial (P < 0.05). The relative contribution of fat oxidation to the energy expenditure showed significantly higher values (P < 0.05) in the Repeated trial than in the Single trial during the recovery period. These results indicate that repeated bouts of exercise cause enhanced fat metabolism compared with a single bout of prolonged exercise of equivalent total exercise duration.