3. Salmon. This oily fish is very healthy due to many important nutrients, such as omega-3 fatty acids. They are a good protein source and a good fat source. There is also a good amount of iodine for your thyroid function and to keep your metabolism optimal. The omega-3 fatty acids can reduce inflammation, which plays a role in metabolic disease and obesity. Also try trout, sardines, mackerel, and other oily fishes.