Changes in fatty acid composition in rat adipose tissue induced by dietary obesity.

The aim of the study was to evaluate the effects of cafeteria feeding on the composition of fatty acids in retroperitoneal fat pad and also to determine what happens to fatty acids when rats previously fed the cafeteria diet are returned to regular rat chow. The study of the post-cafeteria rats enabled us to determine the effects of dietary induced excess weight in the absence of artefactual interferences from the diet because these rats, unlike the cafeteria obese rats, ate the same diet as controls. In response to cafeteria feeding there were increases in the majority of adipose tissue fatty acids. However, significant decreases were observed in the relative proportions of 18:2n-6 and in two related n-6 polyunsaturated fatty acids (18:3n-6 and 20:3n-6), as well as in 16:1. In the post-cafeteria obesity model the previous dietary influence on fatty acid composition was still evident. The maintenance of both the high levels and proportions of 18:1 and the decrease of 16:1 percentage in the post-cafeteria rats argues in favour of an alteration in the activity of the elongation metabolic pathway. Certain changes affecting polyunsaturated fatty acid adipose depot composition of obese rats, mainly the decreased levels of 18:2n-6, are long lasting and could be related to the maintenance of the obese status. On the whole, although the fatty acid composition of adipose tissue is influenced by the composition of the diet, there are some differences in both the maintenance of the effects and also in the selectivity of adipose tissue for the different fatty acids of obese and lean rats.