Meal pattern analysis: artifacts, assumptions and implications.

The meal patterns of 12 male Sprague-Dawley rats were monitored continuously for eight consecutive days. During that time, food intake was measured every second, accurate to 0.01 gram. Results from this procedure demonstrated that the correlation between meal size and meal duration was, at best, weak. Further, the correlation between meal size and either the pre or post meal interval was also weak (approximately 0.20). Subsequent re-evaluation of the patterns using different end-of-the-meal criteria resulted in a significant interaction between the end-of-the-meal definition and the strength of the correlation between meal size and post meal interval, with more robust correlations being observed with the use of longer end-of-the-meal definitions. In an attempt to resolve the question of which definition to use, log survivorship analysis was applied to the interval data. Results from that procedure suggest that a 10 minute end-of-the-meal definition is appropriate in most cases in the analysis of daytime patterns, and a 5 minute definition should be used when quantifying nighttime patterns. Under these "data determined" conditions, the correlation between meal size and post meal interval was not statistically significant. The implications of these results with respect to a homeostatic model of feeding behavior are discussed.