The relation between meal size and the time between meals: Effects of cagecomplexity and food cost

Certain popular models of the regulation of food intake predict a positive correlation between the size of a meal and the preceding and/or following i ntermeal interval. However, the reported strength of these prandial correla tions has varied widely in the literature. To determine what factors may in fluence the strength of these relationships, we measured the timing of and amount consumed in meals of laboratory rats as a function of 1) whether the y were housed in isolation or with partial access to peers or a running whe el, 2) whether they were disturbed daily or weekly for maintenance procedur es, and 3) whether food was free or contingent on operant responding. We al so compared two definitions of "meal" and "intermeal interval." Strong pran dial correlations were found only occasionally. Caging, food cost, and main tenance frequency did not affect the size of the correlations, although the se factors did influence the rats' meal patterns. We conclude the regulatio n of food intake cannot be explained by models relying on a regular relatio nship between meal size and intermeal interval. (C) 1999 Elsevier Science, Inc.