Human aging is often associated with compromised regulation of energy balance and inappropriate body weight and body composition. Among adults older than 60 years, about 38% are overweight, 15% are obese, 20% are underweight, and 20-50% have sarcopenia. Safe and effective therapies to help elderly people maintain a healthy body weight and composition are sought. Pilot research shows that the ingestion of a food in fluid form elicits a weaker appetitive response, differential changes in glucose, insulin and leptin (and possibly neuropeptide Y and cholecystokinin) (each regulators of appetite), and an increase in food intake at the next meal, compared to eating a solid food. Thus, the ingestion of energy as fluids might help underweight elderly people increase energy intake and body weight, while the ingestion of solids should be more satiating and help overweight elderly people maintain or lower body weight. Research also shows that resistive exercise (RE) and training influence the regulation of energy balance and help to treat sarcopenia. Limited data indicate that RE influences the dietary response to nutrient supplementation in elderly people, and that different responses might occur when the supplement is consumed in fluid vs. solid form. This proposal entails three studies designed to more fully document the differential dietary responses to energy-yielding fluids vs. solids in 65-90 year-old persons who are sedentary or perform RE, to examine potential contributory mechanisms, and to test the therapeutic application of this knowledge. Study 1 will contrast the acute effects of fluid and solid food ingestion, coupled with RE, on satiation, satiety, and feeding. Study 2 will document potential mechanisms to explain findings from Study 1 by assessing fluid vs. solid foods and RE on specific gastrointestinal and endocrine regulators of satiety (i.e., glucose, insulin, leptin, neuropeptide Y, cholecystokinin and gastrointestinal transit time). Study 3, a cross-over study with two 8-week trials, will assess in sedentary and resistive training elderly persons the effects of the chronic intake of fluid vs. solid nutritional supplements on appetite, dietary intake, energy expenditure, body weight and composition, and the regulators of satiety listed in Study 2. Documentation of differential responses to energy-yielding fluid and solid foods in sedentary and RE elderly people will provide a strong foundation for integrative recommendations to promote safe and effective weight changes in elderly people.
