Effects of food form on appetite and energy intake in lean and obese young adults

Objective: To investigate the independent effect of food form on appetite and energy intake in lean and obese adults using high carbohydrate, fat or protein food stimuli. Design: Crossover dietary challenge with matched beverage and solid food forms: high carbohydrate (watermelon and watermelon juice); high protein (cheese and milk); high fat (coconut meat and coconut milk). Subjects: A total of 120 lean (18-23 kg/m(2); N = 60) and obese (30-35 kg/m(2); N = 60) adults (18-50 years old) with stable body weight. Forty different participants (N = 20 lean and 20 obese) were tested with each of the food systems. Measurements: Appetitive sensations, food palatability and dietary intake. Results: Regardless of the predominant energy source, the beverage food form elicited a weaker compensatory dietary response than the matched solid food form. Thus, total daily energy intake was significantly higher by 12.4, 19 and 15% on days the beverage forms of the high-carbohydrate, -fat and -protein foods were ingested, respectively. This was due more to a weak effect on satiety than satiation. The obese participants had higher energy intake at the lunch, including the beverage high-protein load, but overall differences between lean and obese participants were small and not systematic. Conclusion: Food rheology exerts an independent effect on energy intake. Dietary compensation for beverages is weaker than for solid food forms of comparable nutrient content. Thus, they pose a greater risk for promoting positive energy balance.