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

by Z Y Chen, C R Menard, S C Cunnane

Abstract: Whole-body fatty acid analysis in rats has previously shown that 50-70% of dietary linoleate and alpha-linolenate is beta-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 beta-oxidation of linoleate and alpha-linolenate thereby depleting their whole-body levels. In rats consuming 3% energy as linoleate and 0.15% energy as alpha-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 alpha-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 alpha-linolenate did not occur per se but the partitioning of linoleate and alpha-linolenate was significantly altered by weight-cycling resulting in lower whole-body accumulation and higher apparent oxidation of all polyunsaturates especially linoleate and alpha-linolenate.
pufa
efa

Rats were put on a 4x repeated 24h fast / 3 day feast cycle to see if this would deplete their body stores of essential PUFA fatty acids LA and ALA. The diet was 3% LA of kcals. Fatty acid profiles were obtained during each fast/feast cycle. It was observed that PUFAs were accumulated in body fat at much lower rates than MUFAs + SFAs when compared with a control (ad-lib fed) group. "Apparent" oxidation was calculated by the difference between intake and accumulation + excretion.

PMID: 8672410
Original source: https://pubmed.ncbi.nlm.nih.gov/8672410/