Tuna offers a variety of essential nutrients, including niacin, vitamin B-6, vitamin B-12, phosphorus and selenium. It's also high in protein, which is more filling than either carbohydrates or fat. Choose tuna instead of meat or poultry and you'll also eat fewer calories, making it more likely that you'll lose weight.
Low in Fat and Calories
Tuna is much lower in fat and calories than beef or chicken. You can eat 3.5 ounces of chunk light tuna canned in water for just 86 calories and 1 gram of fat. The same amount of roasted skinless chicken breast has 165 calories and 3.6 grams of fat, and 3.5 ounces of grilled beef tenderloin with the fat trimmed off has 198 calories and 8.3 grams of fat. To lose one pound per week, you need to reduce your calorie consumption by 500 calories per day, burn 500 more calories per day through exercise, or a combination of these two.
Good Source of Protein
In a study published in "Applied Physiology, Nutrition, and Metabolism" in 2007, people who followed a low-calorie diet high in protein, with a ratio of about 1 gram of protein to 1 gram of carbohydrates, lost more weight than people following a control diet with a ratio of 1 gram of protein to 3 grams of carbohydrates. A 3.5 ounce serving of chunk light tuna has 19.4 grams of protein.
Omega-3 Fats and Satiety
While a diet high in omega-3 fats won't necessarily prompt weight loss, it may make it easier for you to lose weight by helping you feel full for longer. People who ate a diet rich in omega-3 fats, with more than 1,300 milligrams per day, experienced less hunger while on a low-calorie diet than people who ate a low-calorie diet that was low in omega-3 fats, with less than 260 milligrams per day, according to a study published in "Appetite" in November 2008. Each 3-ounce serving of chunk light tuna has about 230 milligrams of omega-3 fats.
Don't rely on tuna for your main source of protein while you're trying to lose weight or you may wind up consuming too much mercury. Chunk light tuna is the type of tuna lowest in mercury, so the U.S. Environmental Protection Agency says it is safe to eat up to 12 ounces per week of this type of tuna. Canned albacore tuna is higher in mercury, but you can safely eat up to 6 ounces of this fish per week. Avoid eating big eye and ahi tuna because they are two of the types of fish highest in mercury.