Weight cycling-induced alteration in fatty acid metabolism

Epidemiological studies have suggested that repeated weight cycling over ti me may increase the risk of coronary heart disease. The mechanism involved remains poorly understood, but the change in lipid metabolism during weight cycling has been offered as a possible explanation. The present study inve stigated the effect of weight cycling on the size and fatty acid compositio n of rat fat pads as well as serum cholesterol, triglyceride, glucose, insu lin, and glucagon in rats. Two consecutive weight cycles were induced by 40 % energy restriction followed by ad libitum refeeding of either a moderate- fat (MF; 22% energy) or a high-fat (HF; 45% energy) diet. The lipogenic enz ymes, including fatty acid synthase, acetyl-CoA carboxylase, malic enzyme, pyruvate kinase, and lipoprotein lipase in the weight-cycled (WC) rats fed only the HF diet, yielded an overshoot of activities at the end of two weig ht cycles. These changes were accompanied by an 80% increase in the size of the adipocyte and a 40-50% increase in the size of perirenal and epididyma l fat tissues in HF-WC rats. Regardless of whether the rats were fed the HF or MF diet, all WC rats showed a gradual reduction in linoleic and alpha-l inolenic acid and an increase in palmitic, palmitoleic, and stearic acid in total body lipid. It is concluded that weight cycling in rats may promote body fatness if an HF diet is consumed and can significantly alter whole bo dy fatty acid balance irrespective of whether they consumed an MF or HF die t. Most importantly, the weight cycling led to an overshoot or fluctuation of serum cholesterol, triglyceride, glucose, insulin, and glucagon. If weig ht cycling is associated with an increased risk of cardiovascular disease, then, part of the mechanism may involve the changes in these risk factors.