Higher Fat Oxidation When Post-Meal Exercise Is Proceeded By Pre-Meal Exercise In Diabetes Patients

Abstract

PURPOSE: The progression from obesity to IGT and type 2 diabetes has been associated with blunted increase in fat oxidation during exercise and an inability to switch to carbohydrate oxidation after meal consumption. In healthy individuals, it has been demonstrated that dividing the exercise session in smaller bouts increases fat oxidation during exercise. Our aim was to compare the fat oxidation rates during exercise performed close to a standard meal. Therefore, 40 minutes of moderate-intensity aerobic exercise were performed either in a single post-meal session (ContEx) or in split in two 20-minute bouts, one before and the other after standard lunch (SplitEx). METHODS: Nine type 2 diabetes patients underwent two different experimental sessions, ContEx and SplitEx. A portable metabolic cart was used to measure respiratory fluxes of O2 and CO2, and thus calculate respiratory exchange rate and fat oxidation rate. Exercise intensity was set at 50% of the heart rate reserve, for a total of 40 minutes accumulated in either a single bout after a standard lunch (55% CHO, 25% fat, 20% protein) or in two bouts before and after lunch. RESULTS: Fat oxidation rate was significantly higher during the SplitEx compared to the ContEx experimental session (.42 ± .26 g*min-1 vs .28 ± .20 g*min-1, P = .04). When dividing the 40-min sessions in two 20-min sessions, i.e. pre and post meal bouts of SplitEx, and first 20 min and second 20 min of ContEx, fat oxidation rate was significantly higher in the post meal bout of SplitEx compared to the pre meal Splitex and the first and second 20 minutes of ContEx (.46 ± .25 g*min-1 vs .37 ± .27 g*min-1 vs .27 ± .2 g*min-1 vs .28 ± .18 g*min-1, P < .05). CONCLUSIONS: Exercising before a meal improves fat oxidation of a second bout of exercise in diabetes patients. This priming effect of prior exercise appears to persist even when insulin levels are high, like the early postprandial state, time when fat oxidation is expected to be low.