Sex-dependent association between omega-3 index and body weight status in older Australians

Background/objectives: Restricting energy intake for weight management in older adults has potential to adversely affect nutritional status and result in impairment of an already compromised immune system. Investigation of alternative strategies to combat adiposity and sustain lean muscle mass in older adults are warranted to minimise the risk of developing chronic diseases. Long chain omega-3 polyunsaturated fatty acids (LCn-3PUFA), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may play an important role through their impact on increased fat oxidation and reduced inflammation. This study aimed to examine the association between erythrocyte membrane LCn-3PUFA and anthropometric measures in an older population. Subjects/methods: A cross-sectional sample of older adults (n = 620; age 65–95 years; 56.3% females) from the Retirement Health and Lifestyle Study (RHLS) was analysed. Anthropometric measurements, including height, weight, body mass index (BMI), waist (WC) and hip circumference (HC) were taken. The fatty acid composition of erythrocyte membranes was analysed via gas chromatography (GC) to determine the omega-3 index (%EPA plus %DHA). Results: An inverse association was detected between the omega-3 index and anthropometric measures, BMI (r = −0.076, p=0.06), WC (r = −0.118, p < 0.01) and waist-to-hip ratio (WHR; r = −0.149, p < 0.001). Stratification of data by sex (females, n = 349; males, n = 271) indicated that these associations were sex-specific. Females displayed an inverse association between the omega-3 index and BMI (r = −0.146, p < 0.01) and WC (r = −0.125, p < 0.05). In contrast, no significant association between the omega-3 index and anthropometric measures was detected in males. After correcting for the potentially confounding effects of age, household income, fish oil supplement status, daily dietary energy intake and total physical activity times, the omega-3 index was inversely associated with BMI and WC in females but not males. Conclusions: Omega-3 status was associated with weight status, particularly in older women but not in men. These results suggest the need for sex-based intervention trials to examine the role of dietary intake and/or supplementation of LCn-3PUFA in weight management of older adults.