Changes in lipogenesis and lipolysis associated with recovery from reversible obesity in mature female rats

Reversible obesity provides a model for demonstration of weight regulation in mature animals. Changes in body composition and in vitro adipose and hepatic lipid synthesis and adipose lipolysis of rats recovering from enforced weight gain were examined to determine whether correction of weight was facilitated by metabolic changes independent of those resulting from hypophagia and negative energy balance. Female Sprague-Dawley rats (200 g) were divided into three groups. Controls ate ad libitum, tube-fed control rats were weight matched to controls. Two-hundred percent-fed rats were tube-fed twice control intake. After 26 days tube feeding stopped and a subgroup from each treatment was killed for determination of body composition and in vitro tissue metabolism. Further subgroups were examined 5, 10, 15, and 36 days later. At the end of overfeeding 200%-fed rats were hypophagic and had high rates of adipose and hepatic lipid synthesis, which soon returned to normal. Gross changes in body fat mass were corrected by hypophagia and increased adipose lipolysis. The remaining small excess in body fat appeared to be corrected by decreased basal and insulin-stimulated adipose fatty acid synthesis when food intake had returned to normal.