The effects of ovariectomy and lifelong high-fat diet consumption on body weight, appetite, and lifespan in female rats

In females, ovarian hormones play pivotal roles in metabolic, appetite, and body weight regulation. In addition, it has been reported that ovarian hormones also affect longevity in some species. Recently, it was found that the consumption of a high-fat diet aggravates ovariectomy-associated metabolic dysregulation in female rodents. The aim of this study was to investigate the hypothesis that long-term high-fat diet consumption and ovariectomy interact to worsen body weight regulation and longevity in female rats. At 21 days of age, female rats were weaned and randomly divided into two groups, one of which was given the high-fat diet, and the other was supplied with standard chow. At 23 weeks of age, each group was further divided into ovariectomized and sham-operated groups, and then their body weight changes, food intake, and longevity were measured until 34 months of age. The sham – high-fat diet rats exhibited greater body weight changes and higher feed efficiency than the sham – standard chow rats. On the other hand, the ovariectomized – high-fat diet and ovariectomized - standard chow rats displayed similar body weight changes and feed efficiency. The sham – high-fat diet and ovariectomized – standard chow rats demonstrated similar body weight changes and feed efficiency, indicating that the impact of ovariectomy on the regulation of body weight and energy metabolism might be similar to that of high-fat diet. Contrary to our expectations, ovariectomy and high-fat diet consumption both had small favorable effects on longevity. As the high-fat diet used in the present study not only had a high fat content, but also had a high caloric content and a low carbohydrate content compared with the standard chow, it is possible that the effects of the high-fat diet on body weight and longevity were partially induced by its caloric/carbohydrate contents. These findings indicate that the alterations in body weight and energy metabolism induced by ovariectomy and high-fat diet might not directly affect the lifespan of female rats.

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