Comparison of long-term feeding pattern between male and female Fischer 344 rats: influence of estrous cycle.

We studied the effect of gender on food intake, meal number, and meal size in eight 10-wk-old female and seven age-matched male Fischer 344 rats for 44 consecutive days. Although food intake (g/100 g body wt) was similar in males and females (5.42 +/- 0.10 vs. 5.13 +/- 0.13 g food.day-1.100 g body wt-1, respectively; not significant), weight gain in males was approximately seven times greater than in female rats (1.49 +/- 0.07 vs. 0.21 +/- 0.03 g/day, respectively; P < 0.001). During this time, males had a relatively constant food intake. They increased their meal size but decreased their meal number. In female rats, food intake was relatively stable for the duration of the study, despite cyclically and reciprocally recurring changes in meal number and meal size, which are synchronized with the estrous cycle. Data confirm that net food intake is a dynamic process and suggest that, in the rat, the homeostasis of food intake in response to external as well as internal stimuli is maintained via the modulation of meal number and size.