Calorie and nutrient intakes of elderly and young subjects measured under identical conditions.

The calorie and nutrient intakes of elderly and young healthy males and females were monitored for four days at the MIT Clinical Research Center. Subjects were free to select foods for meals and snacks from among a variety of high protein and high carbohydrate foods; when necessary, fat was added to make the foods isocaloric. The elderly subjects consumed significantly fewer calories, carbohydrates, and fat than the young subjects, both absolutely and when adjusted for differences in body weight (p less than .001). Mealtime protein intake when adjusted for body weight was similar among males of both age groups and significantly greater than the intakes of both young and elderly females (p less than .001). However, young males consumed more protein from snacks than young females or older adults and thus exhibited the highest daily protein intakes. The two age groups differed significantly in their pattern of food intake from meals and snacks. Elderly adults consumed almost 85% of their total calories from meals, whereas the younger adults consumed about 72% (p less than .001) from meals. Both groups snacked mainly on carbohydrate-rich foods. The elderly subjects consumed significantly fewer snacks than the young; their daily average consumption was 2.2 and that of the young, 4.5 (p less than .001). The persistence of different patterns of food intake between young and elderly individuals when measured under identical clinical conditions suggests that age per se, in addition to age-associated lifestyle changes, may affect eating behavior.