Docosahexaenoic Acid at 0.4% of Dietary Weight Enhances Lean Mass in Young Female Sprague-Dawley Rats

Background: Docosahexaenoic acid (DHA; 22:6n-3) is an n-3 (omega-3) fatty acid known for beneficial effects on body composition. Objective: The objective of the study was to test the dose response of lean and fat mass to DHA in healthy growing female rats. Methods: Female Sprague-Dawley rats (7 wk at baseline; n = 12/diet) were randomly assigned to receive a control (AIN-93M; 60 g soybean oil/kg diet) or experimental diet for 10 wk. Experimental diets contained 0.1%, 0.4%, 0.8%, or 1.2% DHA (wt:wt of total diet). Imaging for whole-body and abdominal composition was conducted using dual-energy X-ray absorptiometry and microcomputed tomography, respectively, at weeks 0, 5, and 10. Fatty acid profiles of several tissues were analyzed using gas chromatography. Serum leptin, C-reactive protein, and plasma insulin-like growth factor I concentrations were measured at each time point using immunoassays. Data were tested using Pearson's correlations and mixed-model ANOVA. Results: No differences were observed in weight at baseline or food intake throughout the study. Overall, a 6% increase (P < 0.05) in whole-body and abdominal lean mass was observed in the 0.4%-DHA diet group compared with the control diet group. Moreover, the abdominal visceral fat mass was 31.4% lower in rats in the 0.4%-DHA than in the 1.2%-DHA diet group (P < 0.001). Rats in the 1.2%-DHA diet group showed greater percent differences in whole-body (32.5% and 40.6% higher) and in abdominal (33.9% and 49.4% higher) fat mass relative to the 0.1 %- and 0.4%-DHA diet groups, respectively (P < 0.01). Accordingly, serum leptin concentration was lower in the 0.1 %-DHA (38.2%) and 0.4%-DHA (43.8%) diet groups (P < 0.01) than in the 1.2%-DHA diet group and positively related to whole-body fat mass (r = 0.91, P < 0.0001). Conclusion: Dietary DHA at 0.4% of dietary weight effectively enhances lean mass and proportionally reduces fat mass in growing female rats.