Lean Male High- and Low-fat Phenotypes--different Routes for Achieving Energy Balance

Objective: This study investigated how energy expenditure may contribute to energy balance in lean male individuals consuming a diet either high or low in fat.

Methods: Fifteen high-fat phenotypes (HF) and 15 low-fat phenotypes (LF) participated in the study. Energy intake and macronutrient intake variables were assessed using a food frequency questionnaire and 3 day food diaries. Total energy expenditure (TEE) was estimated from 24h heart rate monitoring and factorial methods. Habitual physical activity was measured using the Baecke questionnaire.

Results: There were no anthropometric differences between HF and LF. HF had a significantly higher heart rate over 24 h; this was particularly evident during the sleeping phase. There were no differences in TEE between HF and LF, but HF were more sedentary than LF.

Conclusions: In these young male subjects a high fat intake was associated with increased sedentariness; however, higher heart rates (basal and post-meal) could indicate that energy balance was achieved by relatively high basal metabolism and an increase in dietary-induced themogenesis (physiological route). In contrast LF could maintain energy balance through relatively high levels of physical activity (behavioural route).