DEPLETION OF LINOLEATE INDUCED BY WEIGHT CYCLING IS INDEPENDENT OF EXTENT OF CALORIE RESTRICTION

Recent epidemiological studies have suggested that weight cycling indu ced by repeated dieting over time may increase the risk of cardiovascu lar disease. It is speculated that the increased mortality from corona ry heart disease for people with a history of excessive weight cycling could be attributed to change in lipid metabolism. Previous studies h ave demonstrated that repeated cycling of 100% food restriction follow ed by ad libitum refeeding caused a depletion of linoleate and alpha-l inolenate 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% ca lorie restriction, 60% calorie restriction, and 36% calorie restrictio n, respectively, followed by ad libitum refeeding. As the consequence of the two weight cycles, linoleate and linolenate were decreased, whe reas myristate, palmitate, and palmitoleate were proportionally increa sed in carcass and adipose tissue lipids. The results of all three exp eriments showed a preferential depletion of linoleate and alpha-linole nate without changes in final body weight, total body fat, and adipose tissue pads in the weight-cycled rats. In addition, the triacylglycer ol species profile in the adipose tissue of weight-cycled rats was sig nificantly remodeled, with a proportional depletion of linoleate-enric hed triacylglycerol species (LLL, LLO, and LLP where L, O, and P are l inoleic, oleic, and palmitic acid, respectively) and a proportional ac cumulation of palmitate-enriched triacylglycerol species (OPPo, PPPo, and PPP, where Po is palmitoleic acid). We conclude that weight cyclin g changes the ratio of polyunsaturated fatty acids to saturated fatty acids and remodels the adipose tissue triacylglycerol species profile in rats.