Effects of exercise intensity and duration on fat metabolism in trained and untrained older males

Advancing age is associated with changes in fat and carbohydrate (CHO) metabolism, which is considered a risk factor for cardiovascular disease and diabetes. The effects of exercise intensity and duration on fat and CHO metabolism in elderly male subjects were investigated in the present study. Seven trained (63.7 +/- 4.7 years) and six untrained (63.5 +/- 4.5 years) healthy males performed three 30 min trials on a cycle ergometer at 50, 60 and 70% (V) over dot O-2max and two other trials at 60 and 70% (V) over dot O-2max in which the total energy expenditure was equal to that for 30 min at 50% (V) over dot O-2max. Respiratory measures were undertaken throughout the exercise and blood samples taken before and immediately after each trial. Statistical analyses revealed a significant effect of exercise intensity on fat oxidation when the exercise durations were equated as well as when the energy expenditure was held constant for the three trials, though no training effect was noted. Total carbohydrate oxidation increased significantly with exercise intensity (P < 0.05) and with training. Significantly higher levels of non-esterified free fatty acid (NEFA) and glycerol were observed for trained compared with untrained though not for B-hydroxybutyrate (3-OH) or insulin. No differences in NEFA, glycerol, 3-OH were evident for increases in exercise intensity. Carbohydrate and fat oxidation are significantly affected by exercise intensity in elderly males, although only CHO oxidation is influenced by training. Furthermore, training-induced increases in the availability of NEFA and glycerol are not associated with an increase in fat oxidation, rather an increase in CHO oxidation.