Weight loss induced by a hypocaloric diet with or without fish oil supplementation re-established iron and omega-3 fatty acid homeostasis in middle-aged women with obesity: A post-hoc analysis of a randomized controlled trial

Objective: Middle-aged women with obesity are at increased risk of iron overload and iron disorder is known to disrupt n-3 polyunsaturated fatty acid homeostasis. We evaluated relationships between pretreatment hemoglobin and n-3 polyunsaturated fatty acid levels, and tested whether pretreatment hemoglobin contributed to inter-individual variability in weight loss with special focus on changes in body weight, iron and n-3 polyunsaturated fatty acid profiles. Study design: 117 middle and older aged women with obesity and more than two metabolic abnormalities were randomized to a 12-week hypocaloric diet without or with fish oil supplementation. Blood iron biomarker and erythrocyte membrane phospholipid profiles were evaluated. Main outcome: The absolute change from baseline to week 12 in serum iron and erythrocyte n-3 polyunsaturated fatty acid levels according to pretreatment hemoglobin tertiles and fish oil supplementation. Results: A Pearson correlation analysis showed that pretreatment hemoglobin levels were negatively correlated with linoleic acid (r = −0.231), α-linoleic acid (r = −0.279), and n-3 polyunsaturated fatty acid (r = −0.217) (all p < 0.05). Dietary weight loss markedly enhanced erythrocyte membrane lipids of linoleic acid, α-linoleic acid, and n-6 and n-3 polyunsaturated fatty acid only in those women with the highest pretreatment hemoglobin levels (tertile 3) (all p < 0.05). Fish oil supplementation increased bioavailable iron in women with moderate pretreatment hemoglobin levels (tertile 2) (p < 0.05) and, to a lesser extent, prevented a reduction in circulating iron in those with the lowest hemoglobin levels (tertile 1). Conclusion: Dietary weight loss is an effective treatment program to manage obesity-related iron and n-3 polyunsaturated fatty acid disorders, particularly for middle-aged women with obesity and iron overload.