The present study concerns the metabolic and hormonal effects of dietary w3 and w6 fatty acids in rats exposed to a fructose-rich diet. Four groups of 6 rats each were exposed from the 8th week after birth and for the ensuing 8 weeks to diets containing either 64% (w/w) starch and 5% sunflower oil, or 64% fructose and either 5% sunflower oil, 3.4% sunflower oil and 1.6% salmon oil, or 3.4% sunflower oil and 1.6% safflower oil. The time course for changes in food intake, body weight, plasma D-glucose and insulin concentrations was monitored throughout the experiment. At day 50, an intraperitoneal glucose tolerance test was performed after overnight starvation. At sacrifice, other variables, e.g. the percentage of glycated hemoglobin and plasma concentration of D-fructose and albumin, were also measured. Last pancreatic islets were isolated from each group of rats and incubated in vitro for measurement in insulin secretion and content upon exposure to several distinct nutrients secretagogues, as well as D-[U-14C] glucose oxidation and D-[5–3H]glucose utilization. Several variables, including the insulinogenic index and HOMA index for insulin resistance, were found to differ significantly in the w3-depleted rats exposed to the starch- or fructose- containing diet. In the latter case, significant effects of partial substitution of sunflower oil by either salmon or safflower oil were also documented.