Energy and macronutrient balances for humans in a whole body metabolic chamber without control of preceding diet and activity level

Objective: To examine the relationships between 24 h energy and macronutrient balances in a whole body metabolic chamber subsequent to periods when subjects maintained their normal food intake and physical activity levels. Subjects: Thirteen males and 17 females were studied for two 24 h sessions while consuming an estimated isocaloric diet with a food quotient of 0.85. Measurements: Energy expenditure and macronutrient oxidation rates were measured twice for 24 h in a whole body indirect calorimeter. Results: Positive and significant correlations were evident between energy and lipid balances (r=0.38, P<0.05 and r=0.54, P<0.01, respectively) and differences between the two sessions for energy and lipid balances were also significantly correlated (r=0.40, P<0.05). Accounting for carbohydrate or protein balances improved the strength of each of these associations. Conclusion: These results indicate that for subjects in a small but significant positive energy balance, with uncontrolled diet and activity preceding their metabolic chamber sessions, that 24 h energy balance is positively correlated with lipid balance. Accounting for associations between lipid, carbohydrate, protein and energy balances, improved the strength of the association between 24 h lipid and energy balances. The implications of these results are that in these conditions modifications to lipid balance are important for weight maintenance.