Spontaneous human meal patterns are related to preprandial factors regardless of natural environmental constraints

There is a positive relationship between the amount people eat in a meal and the length of time since the previous meal (preprandial correlation). This study attempted to ascertain whether this correlation occurs due to environmental constraints on eating. Eight male and 30 female undergraduate students were instructed to list everything they ate and when they ate it. They were asked to make a recording in a diary of their eating and drinking throughout a 9 day period. They were also instructed to indicate whether the meal was spontaneous, in response to hunger or the desire for food, or constrained, determined by external factors. The amount of food energy in each meal was then calculated, and the amount remaining in the stomach at the beginning and end of each meal was estimated with a mathematical model. These data were then correlated with the duration of the intervals preceding and following the meals. The amount eaten in the meals was found to be predictable on the basis of preprandial factors regardless of whether the meal was initiated spontaneously or under environmental restrictions. Significant preprandial correlations were found for both constrained and spontaneous meals. No relationship was found between the amount ingested in the meal and the following interval (postprandial correlation) even when only the meals preceding a spontaneous meal were correlated. There were no significant correlations between the proportion of the meals that were constrained and the magnitude of either the preprandial or postprandial correlations. The findings suggest that humans initiate eating either in response to an externally determined schedule or to a learned schedule when constraints are not present.(ABSTRACT TRUNCATED AT 250 WORDS)