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Is Fish Good For Weight Loss Or Fattening?

Putting together your weight loss diet can be a challenge with all the possibilities. What about fish, is it good for weight loss or fattening?

Fish are a type of meat that is generally considered very healthy. You do have to keep in mind that some types of fish contain substances like mercury that should be avoided in large amounts.

While different types of fish will have slightly varying nutritional contents, generally many people will benefit in terms of weight loss by eating more fish.

Find out just how good they are, what types of fish to avoid, how much fish you want to eat, and how to cook fish when trying to lose weight.

Example nutritional values of fish

To get a nutrition content that is more or less a good representative we will show the four middle options out of our list of fish for weight loss and use the more optimal of the two median fish, the halibut fish, for the rest of this article.

Below you can find a table with these four options with the most relevant nutrients 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 sea bass (1), halibut (2), tuna (3), and salmon (4) to compare.

Values Per 100gSea BassHalibutTunaSalmon
Calories124 calories140 calories184 calories182
Protein23.6 g26.7 g29.9 g25.4

In the rest of this article you will find out how fish generally compares to other whole foods for weight loss.

Salmon and asparagus to cook in an oven

Micronutrients in fish

The first thing to look at is the amount of micronutrients in fish.

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 halibut provides you with approximately (2):

  • Selenium: 67% of the DV (Daily Value)
  • Niacin: 36% of the DV
  • Phosphorus: 28% of the DV
  • Magnesium: 27% of the DV
  • Vitamin B12: 23% of the DV
  • Vitamin B6: 20% of the DV
  • Potassium: 16% of the DV

And some other vitamins and minerals in less significant amounts. The amount of other vitamins and minerals in fish is generally good compared to many other whole foods.

If you have trouble reaching your daily vitamin and mineral goals fish, and in particular halibut, can help you a nice amount with a few of these goals.

One thing you do have to keep in mind is that you can also consume too much of certain vitamins and minerals. In the case of a few types of fish, you want to keep an eye on selenium.

There is a Tolerable Upper Intake Level (UL) of selenium. In simple words that means that too much selenium can cause negative side effects (5). As an adult you would have to eat over 850 grams of halibut to reach this UL so not very likely (6).

The amount of selenium is still something to keep in mind if you also eat other foods high in selenium like for example brazil nuts.


Another substance you have to keep in mind with fish is mercury. Consuming too much mercury can have severe negative health consequences. Different fish species absorb and retain mercury in varying amounts.

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

Some fish high in mercury include (7):

  • Shark
  • Ray
  • Swordfish
  • Barramundi
  • Gemfish
  • Orange roughy
  • Ling
  • Southern bluefin tuna.

However, these are not the only types of fish that have mercury in them. You can check out the recommendations to find out what kinds of fish you can consume in what amounts per week.

Sliced tuna

Protein in fish for weight loss

Another thing in food that can help you on your weight loss journey is the amount of protein in it.

Cooked halibut contains about 26.7 grams of protein per 100 grams. To compare, there are about 31 grams per 100 grams in cooked chicken breast (8).

Protein is considered to be the most filling of the 3 macronutrients. Eating enough protein will also help you prevent muscle loss. Muscle helps you burn extra calories throughout the day which is very good for weight loss. Protein calories also take your body more calories to process than calories from carbs and fats.

Even though the halibut example contains less than chicken, the amount of protein in fish is large compared to most other foods. You can see the list of fish high in protein to find out what types of fish are especially high in protein.

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

Does fish help you lose weight?

To know whether or not you can eat fish while trying to lose weight you still need a final piece of the puzzle. The number of calories in fish.

Boiled halibut contains 140 calories per 100 grams. 0 of these calories come from carbohydrates.

Fish is definitely suited for low carb diets like the keto diet. Do keep in mind that too much protein can also kick you out of ketosis.

The number of calories in halibut is medium to low compared to many whole foods. Some of the more fatty fish like tuna, salmon, and mackerel take a small jump in calories. That being said even these last fish examples are not that high in calories.

Fruits and vegetables are generally lower in calories than fish but fish do provide you with the important weight loss nutrient protein.

All in all, fish is a rather low-calorie food that can help you feel fuller, build muscle, and preserve muscle. This can help you avoid higher-calorie foods and burn more calories. For most people that, and thus eating more fish, is enough to help them lose weight.

You can likely lose weight without eating any fish but it is one of the more helpful and healthy sources of protein.

If you are gaining weight while eating fish, the first place to look at is the rest of your diet and other lifestyle habits. Even the higher-calorie fish are generally not fattening.

Fish with vegetables to lose weight

Relevant studies

One study compared the effectiveness of cod in calorie-restricted diets over an 8 week period. They divided participants into three groups with the same dietary macronutrient composition.

One group didn’t receive any seafood, one group ate 150 grams of cod three times a week, the third group was given 150 grams of cod five times a week.

The study found a dose dependant increase in weight loss in the groups that ate cod (9).

A second small study found that the participants automatically consumed fewer calories at dinner when they ate a lunch with fish protein compared to eating beef protein (10).

Another study did not find a significant difference between the impact of veal vs fish on appetite sensations (11).

How much fish should you eat?

Nutrition is always a bit of a puzzle in terms of what the perfect diet looks like. It’s a pretty individual thing.

Consuming enough vitamins and minerals is important for both your short and long-term health and weight loss. Fish can help you a lot with consuming enough of these.

Even so, you will need other foods for specific nutrients as well. Something like a fish diet, mostly eating fish, is not recommended.

The 2015-2020 Dietary Guidelines for Americans recommends (12):

  • At least 8 ounces (227 grams) of seafood (less for young children) per week based on a 2,000 calorie diet
  • Women who are pregnant or breastfeeding to consume between 8 and 12 ounces (227-340 grams) of a variety of seafood per week, from choices that are lower in mercury.

These are of course general guidelines. The optimal fish consumption for you personally may be different.

How to cook fish for weight loss

You can implement more fish into your diet in many different ways. Some are better than others for weight loss.

The best fish recipes include this protein source in a healthy way with healthy ingredients. That means preferably boiling but also baking and pan-frying. For example something like fish soup can be a great addition to your weight loss diet.

If you are looking to lose weight you generally want to avoid deep-fried fish recipes, fish & chips, and fish tacos.


Matt Claes

Matt Claes founded Weight Loss Made Practical to help people get in shape and stay there after losing 37 pounds and learning the best of the best about weight loss, health, and longevity for over 4 years. Over these years he has become an expert in nutrition, exercise, and other physical health aspects.