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Is Tuna Good For Weight Loss Or Fattening?

This article has been Fact-Checked by Kendall Kennedy MS, RD, RYT

Choosing the right protein sources for your weight loss diet can be a challenge. What about tuna, is it good for weight loss or fattening?

Tuna is the name for a kind of saltwater fish consumed all around the world. Even to the point that multiple species of this fish are considered to be vulnerable, and in some cases endangered.

Like most fish, many people will benefit in terms of weight loss by eating more tuna. You do have to keep in mind that tuna contains a lot of mercury, a substance that can cause negative side effects if you overconsume it.

Find out how much tuna you can eat and how tuna compares to other popular protein sources for weight loss.

Micronutrients in tuna

The first thing to look at are the micronutrients in tuna.

Micronutrients are a group of nutrients your body absolutely needs to survive and thrive. Micronutrients include vitamins and minerals. These are involved in basically every aspect of your health, including weight loss.

100 grams of cooked blue fin tuna provides you with approximately (1):

  • Vitamin B12: 181% of the DV (Daily Value)
  • Selenium: 67% of the DV
  • Niacin: 53% of the DV
  • Vitamin A: 50% of the DV
  • Phosphorus: 33% of the DV
  • Vitamin B6: 26% of the DV
  • Thiamin: 19% of the DV
  • Riboflavin: 18% of the DV
  • Vitamin B5: 14% of the DV

And a few other micronutrients in smaller amounts. Tuna is a complete powerhouse when it comes to micronutrients, there are not many foods that contain more vitamins and minerals per 100 grams.

The problem with tuna: mercury

While the amount of vitamins and minerals in tuna looks promising, there is a problem with certain species of fish, including tuna.

There are fish that contain a substance called mercury in bigger than usual amounts. Different fish species absorb and retain mercury in varying amounts.

Consuming too much mercury can have severe negative health consequences.

The amount of mercury in tuna depends on the kind of tuna. Even so, all of them contain a relatively high amount of mercury compared to the recommended daily intake and compared to other kinds of fish.

For pregnant women high mercury foods are out of the question. For other people the recommendations vary.

If you want to be completely sure, you would not consume tuna altogether. You can check out the recommendations on the webpage linked in the paragraph above to find out what kinds of tuna, and other fish, you can consume in what amounts per week.

Micronutrients in tuna for weight loss

Protein in tuna for weight loss

If you do decide to consume tuna, another important thing to look at for weight loss is the amount of protein in it.

This kind of tuna contains around 29.9 grams of protein per 100 grams. One drained can of tuna (79 g) would contain about 23.6 grams of protein.

Tuna fish is a great source of protein per 100 grams, it is even the highest option on this list of fish high in protein.

Protein is considered to be the most filling of the 3 macronutrients. Hunger and cravings can be a big pitfall for people trying to lose weight, so avoiding this is a big plus.

Eating enough protein will also help you prevent muscle loss. Since, muscle helps you burn extra calories throughout the day this is another big plus for protein and tuna for weight loss.

Do keep in mind that overdoing it with protein isn’t good either

Will tuna help you lose weight?

You still need the total amount macronutrients, the amount of calories in tuna.

Tuna contains around 184 calories per 100 grams. One can of drained tuna (79 g) would contain about 45 calories.

All of these calories come from fat and protein in tuna. This makes tuna a great option for low carb diets like the keto diet. Keep in mind that too much protein can also kick you out of ketosis.

The amount of calories in tuna is medium compared to a lot of other meats for weight loss. Also compared to other fish, tuna is in the middle of the pack when it comes to calories. Most vegetables and fruits are lower in calories.

Even with that in mind tuna is a great food option when trying to lose weight. It will help you feel fuller without adding too many calories to your diet. This will help you avoid higher calorie foods.

In theory you can overdo it with tuna in terms of calories, in that case tuna could be fattening. In reality you will likely feel too full to reach that point.

You do have to keep in mind the mercury content of tuna. If you choose to eat this meat consume the right kind of tuna and don’t consume this fish too often.

While tuna can be a great food option, it is not a must. You might also be able to get the nutrients in tuna from other sources that don’t contain such large amounts of mercury.

Can I eat tuna every day and lose weight?

It should be possible to eat tuna every day and lose weight. However, due to the mercury content in tuna it is probably not smart to consume this fish every day.

Will tuna help you lose weight

Tuna vs other popular protein sources for weight loss

You now know how good tuna is for weight loss but how does it compare to certain other popular protein sources? Find out how good tuna is for weight loss vs salmon, sardines, chicken, and mackerel.

You do have to keep in mind that there are variations, even of the “same” kind of fish. These are examples, in reality the nutritional values may be slightly different for the protein sources you buy. These comparisons will also not look at the different mercury levels.

Tuna vs salmon

Salmon is another very popular kind of fish. If you’re only looking at calories, in this example salmon contains about the same amount of calories. Tuna contains around 184 calories per 100 grams vs the 182 calories per 100 grams of salmon (2).

The protein content of these foods is comparable, 29.9 grams per 100 grams in tuna vs 25.4 grams per 100 grams in salmon. Lastly, they are very similar in the amount of vitamins and minerals.

Mercury aside, this example of tuna is likely better for weight loss than this example of salmon. That being said, eating salmon 2x/week is still a heart healthy option that may aid in weight loss.

Tuna vs sardines

Another popular kind of fish is sardines. Sardines are a small amount higher in calories, 208 calories per 100 grams (3).

Sardines have about 24.6 grams of protein per 100 grams vs the 29.9 grams of tuna. Sardines have slightly higher amounts of vitamins and minerals per 100 grams.

This kind of tuna will most likely be better for weight loss than the sardines from this example.

Tuna vs chicken

Next there is tuna vs chicken. 100 grams of cooked chicken breast is slightly lower in calories than 100 grams of this kind of tuna, 165 calories vs the 184 calories per 100 grams of tuna (4).

Boiled chicken breast contains about 31 grams of protein per 100 grams. These 2 foods are about the same when it comes to the quantity of vitamins and minerals but with a different focus of vitamins and minerals.

All in all, cooked chicken breast will likely be better than this example of tuna for weight loss.

Tuna vs mackerel

Lastly there is the comparison of tuna vs mackerel. This example of mackerel contains about 201 calories per 100 grams (5).

Mackerel is lower in protein, 25.7 grams per 100 grams, than tuna, 29.9 grams per 100 grams. Tuna also has a slightly higher amount of vitamins and minerals.

This tuna will most likely be better for weight loss than the mackerel.

If you still decide to implement mackerel into your diet keep in mind that mackerel is also relatively high in mercury. Consumption of it should be limited and avoided for pregnant or breastfeeding women.

Chart of tuna vs other popular protein sources

All in all, the differences between these foods won’t make that much of a difference when it comes to losing weight. If you like all these foods equally you might as well choose the ones that are better for weight loss.

The amount of vitamins and minerals in the foods does matter for weight loss and health but you can’t simplify that in one number. You can check out the numbers for tuna (1), salmon (2), sardines (3), chicken (4), and mackerel (5) to compare.

Values Per 100gTunaSalmonSardinesChickenMackerel
Calories184 calories182 calories208 calories165 calories201 calories
Protein29.9 g25.4 g24.6 g31 g25.7 g
Chart of tuna vs other popular protein sources