Inhibition of diet-induced thermogenesis during pregnancy in the rat

Both virgin and pregnant rats were maintained at two different ambient temperatures (28 degrees C and 10 degrees C) for 19 days. Virgin rats maintained their daily food intake and body weight at both temperatures. At 28 degrees C pregnant rats showed a greater daily food intake and body weight than virgin ones and their brown adipose tissue suffered regressive changes in composition when compared with brown fat of virgin rats. At 10 degrees C the increases in daily food intake and body weight of pregnant rats took place from day 15-16 of pregnancy onward and foetuses taken from these pregnant rats were smaller than those taken from pregnant rats at 28 degrees C. It is concluded that pregnant rats at thermoneutrality, although hyperphagic, do not show diet-induced thermogenesis. However, it is proposed that pregnant rats in the cold may show BAT cold-induced thermogenesis.