Fish oil contains omega-3 fatty acids EPA and DHA that have been shown to provide significant health benefits such as reducing the risk of cardiovascular disease, cancer, and diabetes. While flax seed oil contains omega-3 ALA, studies have found it does not provide the same benefits as fish oil because the body cannot efficiently produce EPA and DHA from ALA alone. For these reasons, fish oil is generally a better source of omega-3 fatty acids than flax seed oil for improving health and potentially aiding in weight loss.