Induction of obesity by group housing in female Syrian hamsters.

We examined the effects of group housing on body weight in adult female Syrian hamsters. Over a 10-week period, female hamsters housed in groups of 5 per cage increased their body weight by 61% compared with an 18% increase in body weight for female hamsters housed individually. The divergence in body weight between females housed in groups and females housed individually was evident as early as 2 weeks after the start of the experiment. At the end of the 10 weeks, group-housed females were significantly longer, had a higher percentage of body fat, and larger adrenal glands compared with these measures from individually housed hamsters. These results demonstrate that housing conditions can have a powerful effect on body weight and body composition in female Syrian hamsters. These effects are discussed in the context of social stress mediating obesity in Syrian hamsters, and offer the possibility for a socially based animal model of obesity.