Meal patterns and food selection during the development of obesity in rats fed a cafeteria diet.

Offering preferred foods in addition to laboratory chow led immediately to a marked increase in both mean meal size (MMS) and meal frequency (MF). As body weight increased over a 5 months period, MF declined to a low level but MMS remained high. Within a majority of meals there was substantial consumption of only one food item. Nonetheless, when "mixed" meals were eaten these were usually larger than "exclusive" meals. With more than one preferred food available there was a significant tendency to alternate consumption of food types from one meal to the next. This disappeared at inter-meal intervals longer than 90 minutes. With one preferred food available, only MMS (and not MF) was increased and the degree of hyperphagia and obesity were reduced. The findings suggest the following conclusions: Both palatability (preference value for a particular food) and variety (availability of different types of food) have incremental, but distinguishable, effects on food consumption and mean parameters. Palatability mainly influences meal size, whereas variety exerts an effect on meal size and inter-meal interval. However, the potential effect of variety on overall intake is probably somewhat reduced by the tendency to eat only one type of food in each meal. Obesity has an inhibitory influence on feeding, operating primarily through a reduction in mean frequency.