Depletion of linoleate induced by weight cycling is independent of extent of calorie restriction

Recent epidemiological studies have suggested that weight cycling induced by repeated dieting over time may increase the risk of cardiovascular disease. It is speculated that the increased mortality from coronary heart disease for people with a history of excessive weight cycling could be attributed to change in lipid metabolism. Previous studies have demonstrated that repeated cycling of 100% food restriction followed by ad libitum refeeding caused a depletion of linoleate and alpha-linolenate in rats. The objective of the present study was to test the hypothesis that the weight cycling-induced reduction in linoleate and alpha-linolenate is independent of extent of calorie restriction. Two consecutive weight cycles in three experiments were induced by 100% calorie restriction, 60% calorie restriction, and 36% calorie restriction, respectively, followed by ad libitum refeeding. As the consequence of the two weight cycles, linoleate and linolenate were decreased, whereas myristate, palmitate, and palmitoleate were proportionally increased in carcass and adipose tissue lipids. The results of all three experiments showed a preferential depletion of linoleate and alpha-linolenate without changes in final body weight, total body fat, and adipose tissue pads in the weight-cycled rats. In addition, the triacylglycerol species profile in the adipose tissue of weight-cycled rats was significantly remodeled, with a proportional depletion of linoleate-enriched triacylglycerol species (LLL, LLO, and LLP where L, O, and P are linoleic, oleic, and palmitic acid, respectively) and a proportional accumulation of palmitate-enriched triacylglycerol species (OPPo, PPPo, and PPP, where Po is palmitoleic acid). We conclude that weight cycling changes the ratio of polyunsaturated fatty acids to saturated fatty acids and remodels the adipose tissue triacylglycerol species profile in rats.