[Energy expenditure. How can they be measured?].

Body weight is dependent on the mass of the body and on the fat-free mass. In order to accomplish its mechanical and biochemical functions, the Krebs cycle is activated and generates ATP formation. From ATP, ADP is generated, releasing energy. Total energy expenditure (EE) includes: resting EE, diet-induced thermogenesis, activity-based EE and EE from thermoregulation. They represent 65%, 15%, 20% and 2% of total EE in sedentary human being. The subjects who will being overweight have, as a mean, decreased REE, DIT, PAEE and EETR. At the opposite, the thin subjects have elevated REE, DIT, PAEE and may be EETR. When an obese people is slimming, REE, DIT, PAEE and EETR decrease. When a thin people is gaining weight, REE, DIT, PAEE and EETR increase. This adaptative phenomenon explains why change in body weight and body masses are not linear.