Moderate, selective depletion of linoleate and alpha-linolenate in weight-cycled rats

In rats, the response of adipose tissue composition to a single weight cycle (24-48 h of fasting followed by refeeding) is characterized by a decrease primarily in linoleate and alpha-linolenate, with little or no change in other fatty acids. We tested the hypothesis that during successive weight cycles caused by repeated fasting and refeeding, the depletion of linoleate and alpha-linolenate from whole body stores would be exacerbated despite their adequate availability during the refeeding period. Four complete weight cycles (24-h fasting followed by 72-h ad libitum refeeding) induced a significant quantitative decrease in total n-3 and n-6 polyunsaturates, particularly linoleate and alpha-linolenate, and a simultaneous increase in the accumulation of palmitate, palmitoleate, and oleate in carcass total lipids and in perirenal and epididymal adipose tissue. A significant positive relationship was observed between the increasing ratio of saturates+monounsaturates to n-3 + n-6 polyunsaturates in adipose tissue and the number of weight cycles (r = +0.96, P < 0.0001). The percentage of linoleate and alpha-linolenate in adipose tissue was inversely related to the number of weight cycles. We conclude that, despite providing adequate n-6 and n-3 polyunsaturates in the diet during the refeeding period, weight cycling in young growing rats causes a moderate, selective depletion of linoleate and alpha-linolenate from tissue stores.