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 21days 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 23weeks 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 34months 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.