Social and physiological factors affecting food intake in elderly subjects: an experimental comparative study

The decline in average food intake in elderly people is attributed to both physiological and social factors. These factors are usually studied in isolation. The present study concerns an experiment in which the effect of social setting on food intake is compared with the effect of physiological challenges on food intake in 24 elderly subjects (6 men and 18 women, age: 75 +/- 4.9 years, BMI = 26.6 +/- kg/m2). Physiological effects were assessed using a preload-test-meal design with a no load, 0 kJ; and 4 preload conditions: low carbohydrate/low fat, low energy, 0.4 MJ; high fat, low carbohydrate, medium energy 1.1 MJ; high carbohydrate, low fat, medium energy 1.1 MJ; high fat, high carbohydrate, high energy, 1.8 MJ. The preloads consisted of 300 g of strawberry yogurt drink, and were served at 10:00 a.m. The test-meal, served 90 min after the preload consumption, was a lunch of which subjects could eat ad libitum. Social effects on food intake were assessed by using two social settings at lunchtime: cozy and non-cozy. Dependent variables were food intake at lunch and ratings of appetite assessed before the preload, and between preload and test-meal. Results showed that energy intake at lunch was significantly decreased after the high carbohydrate preload and the high fat-high carbohydrate preload (intake compensation of 23 and 15%, respectively), compared to the no preload condition. The other preloads did not have a significant effect on food intake. Energy intake was of 2.5 +/- 0.5 MJ in the cozy social setting and of 2.5 +/- 0.6 MJ in the non-cozy one. Appetite feelings were generally lower after the preload conditions compared to the no load condition (P < 0.05), but there were no significant effects of the macronutrient or energy content of the preloads on appetite feelings. It is concluded within the context of this study in healthy elderly subjects that food intake response more to physiological challenges than to short-term changes in social settings.