Abstract
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% 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.
Highlights
A characteristic of ageing is an increase in adiposity and loss of muscle mass [1]
No significant main effect of the meals was observed for rates of fat oxidation (F3,21 = 1.8; P = .177), fat oxidation was demonstrably, but nonsignificantly, higher after high fat (HF) (0.26 ± 0.04 g/min) than N (0.21 ± 0.04 g/min), high glycaemic index (HGI) (0.22 ± 0.03 g/min), and low glycaemic index (LGI) (0.19 ± 0.03 g/min)
Pairwise comparisons revealed a significant difference between nonesterified fatty acids (NEFAs) responses to N and HF (P = .02) as well as between HGI and LGI meals (P = .003)
Summary
A characteristic of ageing is an increase in adiposity and loss of muscle mass [1]. Since the increase in adiposity is related to general poor health factors such as an increase in type II diabetes and increased incidence of coronary heart disease, exercise to reduce adiposity is recommended for the ageing population. They demonstrated that the HGI meal resulted in a greater glycemic and insulinemic response during the postprandial period compared with LGI meal This is supported by Stevenson et al [11] who investigated the metabolic responses to HGI and LGI mixed meals after 60-minute exercise at 70%V O2 max and found that significant differences in hyperglycemia and hyperinsulinemia can be achieved repeatedly by changing the Glycemic Index (GI) of the CHO in a mixed meal. They observed that the amount of Journal of Nutrition and Metabolism fat oxidised during the postprandial period following lunch was significantly higher in the LGI than the HGI trial. At least for several hours postprandial, both at rest and during exercise, fat utilisation is depressed after HGI compared with LGI meals
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