The effect of diet alone or in combination with resistance or endurance training on fat oxidation at rest and during exercise

The balance between fat intake and fat oxidation is an important factor in body weight regulation. Following weight loss, fat oxidation is reduced, a condition that favors the regain of weight. The purpose of this study was to determine the effect of weight loss alone or in combination with resistance or endurance training on fat oxidation at rest and during exercise. Twenty-seven obese females were assigned to follow either a 12-week, 1,200 kcal•day −1 diet only (D), diet plus endurance training (DE), or diet plus resistance training (DR) treatment. Habitual physical activity and dietary intake, maximal oxygen uptake (VO_2max), muscular strength, body mass, body composition, and fat oxidation at rest and during exercise were measured at baseline and follow-up. Dietary intake decreased significantly in all treatment groups while habitual physical activity was not significantly different from baseline to follow-up. Both upper and lower-body strength increased significantly in the DR group and VO_2max increased significantly in the DE group, with no significant changes in the other groups. Body mass, BMI, body fat, and fat mass decreased significantly in all groups while fat-free mass increased significantly in all groups. Resting fat oxidation decreased significantly in all groups while there were no significant changes in fat oxidation during submaximal exercise in any group.; The results of this study indicate that the diet was effective in promoting significant changes in body mass and body composition in all treatment groups. This weight loss resulted in a significant decline in the rate of resting fat oxidation, due entirely to a reduction in resting metabolic rate since the respiratory quotient (RQ) was not different following treatment. Although these changes were not significantly different between groups, the magnitude of the changes suggests that resistance training tends to attenuate the decline in resting metabolic rate and fat oxidation associated with weight loss. There were no significant changes in fat oxidation during exercise in any group, but the direction of the small changes in the DE group was in accordance with what the literature suggests following endurance training: a lower RQ and a higher rate of fat oxidation.