Effects of Mixed Isoenergetic Meals on Fat and Carbohydrate Metabolism during Exercise in Older Men

The present study was designed to investigate the effects of four different meals on fat and CHO metabolism during subsequent exercise in elderly males. Eight healthy males (age: 63.3 +/- 5.2 years) reported to the physiology laboratory on four separate occasions, each of which was allocated for the performance of a 30-minute exercise on a cycle ergometer at 60% VO2max after having normal (N), high fat (HF), high carbohydrate high glycaemic index (HGI) and high carbohydrate low glycaemic index (LGI) meals. Fat oxidation during exercise after the meals (HF = 0.26 +/- 0.04 g/min; N = 0.21 +/- 0.04 g/min; HGI = 0.22 +/- 0.03 g/min; LGI = 0.19 +/- 0.03 g/min) was not significant (P > .05), and neither were the rates of carbohydrate oxidation (N = 1.79 +/- 0.28, HF = 1.58 +/- 0.22, HGI = 1.68 +/- 0.22, and LGI = 1.77 +/- 0.21 g/m). NEFA concentration increased after HF (P < .05) but decreased after HGI and LGI (P < .05). Glucose concentration decreased as a result of exercise after HF, and LGI (P < .05) whereas insulin concentration decreased significantly during exercise after N, HF, and HGI (P < .05). It can be concluded that, in elderly males, feeding isoenergetic meals containing different proportions of carbohydrate and fat do not significantly alter oxidation of fat and CHO during exercise in spite of changes in some circulating metabolites.