You can certainly lose weight by eating tuna fish oil benefits. A standard 5 oz. can of tuna fish provides 120 calories, 26 grams of protein, 2 grams of fat. Tuna fish is practically a zero carbohydrate food source so it is convenient for those who are trying an Atkins-type diet. However, only eating tuna fish may present a problem because its low caloric content would probably leave one feeling unsatisfied. For example, if you ate a can of tuna at each of your three meals, you would be ingesting only 360 calories. Further, albacore “white” tuna has more mercury content than light tuna. The FDA recommends eating only 6 ounces of albacore tuna per week. Get a supply of tuna fish to have on hand. You can use solid white or light tuna depending on your preference. If you are only eating tuna, then you will need a minimum of three cans per day.