Small effect of brown adipose tissue and major effect of photoperiod on body weight in hamsters (Mesocricetus auratus).

It has been suggested that brown adipose tissue plays a special role in the control of body weight. This hypothesis was investigated by measuring the body weight of female hamsters over a two month period following removal of interscapular brown adipose tissue. Two groups of animals were used, one maintained on a short day (10:14 light: dark ratio) and the other on a long day (16:8 light: dark ratio) photoperiod. Under both photoperiod conditions hamsters with interscapular brown adipose tissue removed gained somewhat more weight than their corresponding sham operated controls. Photoperiod, however, had a much larger effect on body weight. Hamsters maintained on short days increased their body weight by about 60 percent during the two months of the experiment whereas the hamsters maintained on long days increased their body weight by only about 17 percent. It was concluded that brown adipose tissue plays a small non special role in the control of body weight in the female hamster, but that the light-dark ratio is quantitatively much more important under these experimental conditions.