Energy balances in obese mice

According to most existing theories, the regulation of energy balance is achieved by control of energy intake. This study was undertaken to find out whether there was control of energy output as well. Food intake, energy balance and the feed efficiency of weanling female mice made obese with injections of gold-thioglucose and monosodium glutamate indicate that the obesity is primarly due to an increased energetic efficiency, and suggest that the hypothalamus plays a role in controlling energy output. In the case of treatment with MSG, a relative obesity was observed, i.e. an increase in body fat without any change in body weight. This indicates that the CNS centres for the regulation of body weight and body fat are probably not the same. It is suggested that MSG obesity will be a suitable model for comparative studies of body weight and the regulation of fat content. It is concluded that chemically induced obesity is due more to a lower metabolic rate than to an elevated food intake.