The physiological responses to maximal eating in men

This study investigated metabolic, endocrine, appetite, and mood responses to a maximal eating occasion in fourteen men (mean ±SD: age 28 ±5 y, body mass 77.2 ±6.6 kg, body mass index 24.2 ±2.2 kg·m-2) who completed two trials in a randomised crossover design. On each occasion participants ate a homogenous mixed-macronutrient meal (pizza). On one occasion, they ate until 'comfortably full' (ad libitum) and on the other until they 'could not eat another bite' (maximal). Mean [95% CI] energy intake was double in the maximal (13,024 [10964, 15084] kJ; 3113 [2620,3605] kcal) compared with the ad libitum trial (6627 [5708,7547] kJ; 1584 [1364,1804] kcal). Serum insulin iAUC increased ~1.5-fold in the maximal compared with ad libitum trial (mean [95% CI] ad libitum 51.1 [33.3,69.0] nmol·L-1·4 h, maximal 78.8 [55.0,102.6] nmol·L-1·4 h, p < 0.01), but glucose iAUC did not differ between trials (ad libitum 94.3 [30.3,158.2] mmol·L-1·4 h, maximal 126.5 [76.9,176.0] mmol·L-1·4 h, p = 0.19). TAG iAUC was ~1.5-fold greater in the maximal versus ad libitum trial (ad libitum 98.6 [69.9,127.2] mmol·L-1·4 h, maximal 146.4 [88.6,204.1] mmol·L-1·4 h, p < 0.01). Total GLP-1, GIP, and PYY iAUC were greater in the maximal compared with ad libitum trial (p < 0.05). Total ghrelin concentrations decreased to a similar extent, but AUC was slightly lower in the maximal versus ad libitum trial (p = 0.02). There were marked differences on appetite and mood between trials, most notably maximal eating caused a prolonged increase in lethargy. Healthy men have capacity to eat twice the calories required to achieve comfortable fullness at a single meal. Postprandial glycaemia is well-regulated following initial overeating, with elevated postprandial insulinaemia likely contributing.