To evaluate the influence of ω-3 polyunsaturated fatty acid (ω-3 PUFA) supplementation on body composition, insulin resistance, and lipemia of women with type 2 diabetes, the authors evaluated 41 women (60.64 ± 7.82 years) with high blood pressure and diabetes mellitus in a randomized and single-blind longitudinal intervention study. The women were divided into 3 groups: GA (2.5 g/d fish oil), GB (1.5 g/d fish oil), and GC (control). The capsules with the supplement contained 21.9% of eicosapentaenoic acid and 14.1% of docosapentaenoic acid. Biochemical (glucose, glycated hemoglobin, total and fractional cholesterol, triglycerides, and insulin) and anthropometric (body mass, stature, waist circumference [WC], and body composition) evaluations were performed before and after the 30 days of intervention. Homeostasis model assessment-insulin resistance and the Quantitative Insulin Sensitivity Check Index were used to evaluate the insulin resistance and insulin sensitivity (IS), respectively. GB presented a greater loss of body mass and WC (P < .05), greater frequency of glycemic and total cholesterol reduction, and an increase of high-density lipoprotein cholesterol compared with GA. Thus, a high dose of ω-3 PUFA can reduce IS. A lower dose of ω-3 PUFA positively influenced body composition and lipid metabolism.