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.