Acute effects of oral preloads with increasing energy density on gastric emptying, gut hormone release, thermogenesis and energy intake, in overweight and obese men.

This study investigated the effect of high- and low-energy density preloads on gastrointestinal and metabolic factors, which act to regulate acute energy intake. Sixteen overweight and obese men (BMI range: 27.2-36.5 kg/m2) each received 3 oral preloads in randomised order: i) high-energy-density, high-fat (1.5 kcal/g), ii) low-energy density, high-fat (1.1 kcal/g), and iii) low-energy-density, high-protein (1.1 kcal/g). Over 180 min, gastric emptying, plasma glucagon-like peptide-1 concentrations, and diet-induced thermogenesis were assessed, and subsequent energy intake was determined. Total energy intake did not differ between preloads (high-energy-density, high-fat, 2059±72 kilocalories (kcal); low-energy-density, high-fat, 1876±91 kcal; and low-energy-density, high protein, 1867±63 kcal). Gastric emptying was slower following the high-energy-density, high-fat preload (158±8 min) compared with the low-energy-density, high-protein preload (130±9 min) (p=0.05), but did not differ between the high-energy-density, high-fat and low-energy-density, high-fat (147±8 min) preloads. Plasma glucagon- like peptide-1 did not differ substantially between preloads. Diet-induced thermogenesis was lower following high-energy-density, high-fat (10.4±0.7 %) than low-energy-density, high-fat (14.9±1.2 %) and low-energy density, high-protein (18.1±1.1 %) preloads (p<0.01 for both). We conclude that an increased energy density slows gastric emptying and reduces thermogenesis, but that a high fat content overrides the effect of energy density on gastric emptying. The counter-regulatory modulation of these gastric and metabolic factors may explain, at least in part, the lack of differences in subsequent energy intake in response to oral preloads with increasing energy density.