Repeated pregnancy without lactation: effects on carcass composition and adipose tissue cellularity in rats.

Four groups of Sprague-Dawley rats, 200-225 g, were mated. Two groups of rats were killed after 3 wk of nursing eight pups (PL-1) or no lactation (PNL-1). The remaining two groups went through three cycles of pregnancy/lactation (PL-3) or pregnancy/no lactation (PNL-3) and were then killed for carcass composition analysis. Two virgin groups (CON-1, CON-3) served as age controls and were killed at the appropriate time. There was a gradual reduction in food intake from cycle 1 to cycle 3 for all groups. PL-3 rats ingested significantly more food than PNL-3 rats in pregnancies of cycle 2 and cycle 3. At the end of cycle 1, there was no difference in body weight, carcass weight, fat content and fat cell cellularity in parametrial and subcutaneous fat pads between three groups of rats. However, after three cycles, the PL-3 group had significantly reduced carcass fat content because of a significant reduction in fat cell number. Repeated pregnancy followed by no lactation resulted in greater carcass fat content and fat cell number in the subcutaneous pad than observed in lactating rats, although these increases failed to reach significance when compared with virgin controls. Thus lactation may not only be beneficial to the offspring but also enhances maternal weight loss and prevents obesity in multiparous individuals.