Influence of environmental factors on food intake and choice of beverage during meals in teenagers: a laboratory study.

Environmental conditions influence meal size in adults and children. Intake of sweet drinks could contribute significantly to energy intake and potentially affect body weight, particularly in young individuals. The objectives of the present study were to measure the lunch intake of food and drinks under controlled laboratory settings in teenagers and to compare the influence of different meal conditions. Normal-weight adolescents (fourteen males and fifteen females) participated in four standardised lunches, scheduled 1 week apart. The same popular items (meat dish, dessert, water, juice, soda) were served at all meals. Ad libitum intake was measured under four conditions: subjects ate alone; in groups; alone while viewing television; alone while listening to music. Visual analogue scales were used to assess pre- and post-meal hunger and thirst and meal palatability. Energy, solid food and fluid intake was different (significantly lower) only in the 'eating in group' condition, in spite of identical intensity of pre-meal hunger. More soda was consumed when participants were watching television, and more water was consumed while listening to music. Across all conditions, more soda than water was consumed. Post-meal ratings of hunger, thirst and palatability did not differ between conditions. We concluded that, in teenagers, a 'social inhibition' effect appears rather than the 'social facilitation' previously reported in adults. Although teenagers do not respond to the presence of television or another 'distractor' such as music by eating more, they do ingest more soda when the television is on. The social significance of meals, conditioned responses and habituation to 'distractors' may be different between adolescents and adults.

Influence of dietary restraint and environmental factors on meal size in normal-weight women. A laboratory study.

In a previous study, we observed that the level of dietary restraint in normal-weight women moderated the stimulating effect of environmental stimuli on meal intake. The present study was designed to confirm and extend this observation. The influence of factors previously shown to affect meal size was investigated: presence of other people, television viewing and listening to radio. Two groups of 20 women were recruited, characterized by high versus low restraint. They participated in five standardised ad libitum lunches, under controlled laboratory conditions: subjects ate alone; in groups; listening to a detective story on the radio; watching television (no food cues); watching food advertisements on television. Lunches had identical menu (main dish and dessert) and were scheduled at 1-week intervals. Visual analogue scales were used to assess hunger, fullness and test-meal palatability. Repeated measures ANOVAs revealed no significant main effect of level of restraint and no interaction with meal conditions. Energy and main dish intakes were lower in the group meal condition than in the other four, which did not significantly differ. Group meals were followed by less intense fullness than the other conditions. These observations raise questions about the factors affecting social influence at meal times; gender, level of acquaintance and inhibitory norm are discussed. Our results also suggest that the intake stimulating effects of various external sources of distraction at meal time could vary in different populations.

The effect of Type I diabetes on the eating patterns of free-living French: a diet diary study.

In order to investigate the changes produced by Type I diabetes on the ad libitum eating behavior of free-living humans, 56 French participants with diabetes and 28 healthy controls were paid to maintain detailed food intake diaries for four 7-day periods. The participants with diabetes ate more protein and more frequent meals, ate slightly later and with fewer other people, were less hungry, thirsty, and depressed, but more elated than the healthy participants. Responses to social facilitation, the diurnal rhythm, subjective hunger, the palatability of the food, and the weekend were not affected by the presence of diabetes. The participants with diabetes had significantly larger correlations and regression coefficients for the relationship between meal size and the duration of the before-meal interval. The relationship between meal size and the after-meal interval was strong and positive in all participants. The recorded behavioral characteristics of diabetics may, in part, be accounted for by the nutritional education that is provided as an integral part of treatment. Based upon these results, it was theorized that the glucose regulatory system is an influence on intake, but only one of many that are responsible for the coordination, control, and regulation of nutrient intake in free-living humans.