The Role of Energy Expenditure in the Control of Body Weight (#53)
For true weight maintenance, not only is energy intake required to match energy expenditure but macronutrient intake must balance macronutrient oxidation. However, this equilibrium seems to be difficult to achieve for individuals with low fat oxidation, low energy expenditure, low sympathetic activity or low levels of spontaneous physical activity. Additionally, large variability in weight change is observed when energy excess (or deficit) is imposed experimentally or spontaneously. Clearly the data suggest an involvement of genetics in body weight regulation implying a “normal physiology in an obesogenic environment”. In such a predisposing environment not everyone becomes obese indicating that differences in the propensity to gain weight are due to cognitive factors (e.g. cognition, emotion and restraint) and genetic factors impacting the “normal physiologic” regulation of food intake and energy metabolism.
After a brief description of the methodology to measure energy expenditure, this presentation will be followed by a review from prospective studies: 1) The inter-subject variability of weight change in response to overfeeding or caloric restriction; 2) The association between energy expenditure, sympathetic activity or spontaneous physical activity and body weight change; 3) The impact of macronutrients on energy balance suggesting that carbohydrate balance may represent a potential signal to modulate energy intake. I will then review the potential pitfalls associated with the activation of brown adipose tissue as an obesity therapy. Finally, I will review how the different mathematical modeling approaches can help to assess energy intake in population and possibly in individuals.