Effect of different macronutrients in excess on gastric sensory and motor functions and appetite in normal-weight, overweight, and obese humans.

BACKGROUND: The effects of supplementation with different macronutrients on gastric sensory and motor functions are unclear. OBJECTIVE: We aimed to compare the effects of 2 wk of supplementation with different classes of macronutrients on gastric function, satiation, and appetite in healthy and overweight subjects. DESIGN: In a parallel-group, double-blind study, 52 (14 men, 38 women) healthy normal-weight, overweight, and obese participants [body mass index (BMI; in kg/m(2)): 19.4-47.0] aged 18-64 y were randomly assigned to consume different isocaloric diets (n = 13 per diet group) adjusted for BMI and activity level. The standard diet provided 20% of energy as protein, 30% as fat, and 50% as carbohydrate. The high-protein, high-fat, and high-carbohydrate diets contained 500 additional kcal in each nutrient class. On 3 separate days, we measured gastric emptying of solids, gastric volumes, postprandial symptoms, appetite, and food choice with validated methods. Age, sex, BMI, and baseline satiation were covariates in the analysis of covariance. RESULTS: Fat supplementation was associated with increased maximum tolerated volume (MTV) in subjects with a high baseline MTV (P < 0.05), irrespective of BMI. Gastric emptying and volumes, postprandial symptoms, total calories, and food choices at an ad libitum meal were not significantly different after each dietary preload. Fasting gastric volumes tended to be higher with the high-fat than with the high-carbohydrate or high-protein diets (P 30). CONCLUSION: Supplementation with 500 kcal fat in excess of required calories for 2 wk increased food tolerance in healthy normal-weight and obese subjects with a high baseline MTV without significantly changing gastric motor functions.

Effect of somatostatin analog on postprandial satiation in obesity.

OBJECTIVE: Altered satiation may impact postprandial symptoms and potentially change food intake in obesity. Our aim was to compare effects of octreotide and placebo on postprandial symptoms, satiation, and gastric volumes in obesity. RESEARCH METHODS AND PROCEDURES: In a randomized, parallel-group, double-blind, placebo-controlled study, 26 obese but otherwise healthy participants received 100 mug of octreotide or placebo subcutaneously 30 minutes before each study. Studies were performed on 2 separate days and included validated non-invasive techniques: (99m)Tc-single photon emission computed tomography imaging to measure fasting stomach volume and gastric volume changes after 90 mL of water and 240 mL of Ensure and a standardized nutrient drink test to measure the maximum tolerated volume and postprandial symptoms. RESULTS: Relative to placebo, octreotide increased gastric volume after 90 mL of water; however, fasting and gastric volume change post-Ensure and maximum tolerated volume of Ensure were not different. Octreotide decreased sensations of fullness (p = 0.035) and bloating (p = 0.05) and tended to reduce aggregate symptoms (p = 0.07) after the fully satiating meal. DISCUSSION: In obese individuals, somatostatin analog significantly reduced postprandial sensations after a satiating meal without altering maximum tolerated meal volume or postnutrient gastric volume, suggesting an effect on upper gut sensation. The role of somatostatin as a permissive factor in the development of obesity by reducing postprandial sensations deserves further study.