Macronutrients and Satiety in Older and Younger Adults

To assess if increasing protein intake in older adults will have a compensatory decrease in energy intake due to protein's satiating effects. To compare the effect of meals high in protein, fat and carbohydrate but equal in energy and volume on energy intake and perceived appetite in younger (\<40 years) and older adults (\>65 years). To compare the effect of meals high in protein, fat and carbohydrate but equal in energy and volume on gastric emptying in younger (\<40 years) and older adults (\>65 years).