Accumulation of polyunsaturates is decreased by weight-cycling: whole-body analysis in young, growing rats

Whole-body fatty acid analysis in rats has previously shown that 50–70% of dietary linoleate and α-linolenate is β-oxidized to CO2 and that this value increases with refeeding after a single episode of fasting. Our hypothesis was that repeated fasting-refeeding or weight-cycling would increase the β-oxidation of linoleate and α-linolenate thereby depleting their whole-body levels. In rats consuming 3% energy as linoleate and 0·15 % energy as α-linolenate during a 16 d balance period, 19% of the linoleate consumed accumulated in weight-cycled rats compared with 34% in the free-fed controls (P < 0.01). Similarly, 11% of the α-linolenate consumed accumulated in the weight-cycled rats compared with 22% in the controls (P < 0.01). Arachidonate and docosahexaenoate also accumulated to lower extents in the weight-cycled rats than in the controls. In contrast, whole-body accumulation of palmitate, stearate and oleate was not different between the weight-cycled group and the controls when measured as a proportion of intake or relative to weight gain. Thus, whole-body depletion of linoleate and α-linolenate did not occurper se but the partitioning of linoleate and α-linolenate was significantly altered by weight-cycling resulting in lower whole-body accumulation and higher apparent oxidation of all polyunsaturates especially linoleate and α-linolenate.