Chronic effects of exercise targeted at the level of maximal lipid oxidation (LIPOXmax) on eating behavior in sedentary obese subjects

Introduction. Physical exercise has both a satiating and an orexigenic effect. The latter seems to be favored by glycogen depletion and thus by high intensity exercise. The balance between these two effects is likely to strongly determine the effect of muscle activity on fat loss. Our hypothesis is that the efficiency of training targeted in the zone of maximal lipid oxidation is at least in part explained by alterations in eating behavior. We studied 25 overweight and obese subjects, including 21 women and 4 men. On the whole these subjects lost weight: -2.05 +/- 0.8 kg; P < 0.02 and this loss was due to a loss in fat mass (-1.68 +/- 0.81 kg; P < 0.05) while FFM was preserved. Five subjects (20%) gained weight (ranging from 0.1 to 1.9 kg), two (8%) had a stable weight and 18 (72%) lost weight (from 0.4 to 21.2 kg). After the first session of training: satiety was unchanged, but hunger was increased (1.15 +/- 0.53; P < 0.05) and the subjects were less thinking of food (P < 0.05). Throughout the sessions there was a gradual increase in the satiety score (P < 0.05), and subjects were less thinking of food (P < 0.05). After training, the acute effect of an exercise session on the appetite scale was modified. The acute orexigenic effect (increased hunger) decreases (-1.17 +/- 0.40; P < 0.01) as well as the desire to eat (-1.35 +/- 0.61, P < 0.05), the amount of food we could eat (-1.25 +/- 0.57, P < 0.05) and the will to eat food (-1.78 +/- 0.58, P < 0.01). Caloric intake decreased after 8 weeks by 362.69 +/- 91.2 kcal/d (P < 0.01) due to a decrease in fat intake (0.17 +/- 0.06 g/kg/day; P < 0.02) which was explained in turn by a decrease in the percentage of fat in diet (from 25% to 21% P < 0.05) and reduced snacking that goes from 44% to 18% of subjects tested (P < 0.01). This decrease in snacking is correlated with that of the item "I think about food" on the scale (Spearman rank correlation r=0.634 P=0.003). This work therefore shows that LIPDXmax training in obese subjects increases satiety at rest and decreases the orexigenic effect of a single session, and decreased caloric intake and snacking at a correspondingly lower thoughts directed towards the food, resulting in weight loss in 72% of subjects. The slimming effect of training at LIPDXmax seems to be explained at least in part by an increase in satiating effect and decreased orexigenic effect of exercise, resulting in a measurable decrease in calorie intake. These results thus evidence a new mechanism that increases the interest in this variety of training in the management of obesity. (C) 2015 Elsevier Masson SAS. All rights reserved.