Is Fish Good For Weight Loss Or Fattening?

Photo of author
Last Updated On

Find out whether fish is good for weight loss or fattening so you don’t mess up your diet with the wrong choices.

Fish is generally reasonably low in calories, high in protein, and high in vitamins and minerals.

That means eating fish will likely fill you up enough to consume less of foods that are worse for weight loss.

The extra protein will also help you reach intake levels that help you preserve and build muscle.

If these things apply, fish would help you lose weight.

At the same time, you still need to implement these other changes to see a lot of positive results.

Additionally, you don’t want to forget that certain fish are high in mercury. Overdoing it with these can actually be bad for your health.

Calories in fish and other nutrient examples

As you can expect, different types of fish can vary in terms of calories and other nutrients.

To give you a general idea, you can find the calories and protein in four examples of our list of the best fish for weight loss below.

You can also check out the vitamins and minerals in halibut (1), sea bass (2), tuna (3), and salmon (4) if this is relevant to your goals.

I will also go over whether fish is generally good for weight loss or not in the rest of the article with sea bass as the main example.

Values Per 100gHalibutSea BassTunaSalmon
Calories111 calories124 calories176 calories182 calories
Protein22.5 g23.6 g30.3 g25.4 g
Salmon and asparagus to cook in an oven

Why fish protein matters for weight loss

Looking at the calories in fish is not enough to make any conclusions.

The protein that makes up part of this amount tends to be helpful when trying to lose weight.

Before going into the reasons why, cooked sea bass contains around 23.6 grams of protein per 100 grams (2).

To compare, there are about 25.7 grams of protein per 100 grams in cooked chicken breast (5).

In simpler words, fish tends to be relatively high in protein. This is generally good for weight loss.

The first reason why is that protein is a very filling macronutrient category.

Since many people struggle with hunger and cravings while trying to lose weight, the protein in fish can be valuable.

Additionally eating enough protein helps you preserve and build muscle.

This extra healthy mass will help you burn more calories throughout the day (on top of all the other amazing benefits).

So fish tends to be high in protein which is generally good for weight loss.

If you really like this aspect, you could even focus on the fish highest in protein.

Sliced tuna

Vitamins and minerals in fish

When it comes to the weight loss effects of the vitamins and minerals in fish, it is harder to make specific statements.

Partly because the rest of your diet and habits will influence these effects too.

At the same time, since it is generally smart to consume enough vitamins and minerals, it can be good to take a look at how fish does in this area.

100 grams of sea bass contains the following vitamins and minerals (2):

  • Selenium: 67% of the DV (Daily Value)
  • Phosphorus: 25% of the DV
  • Vitamin B6: 23% of the DV
  • Magnesium: 13% of the DV
  • Niacin: 10% of the DV

And some other vitamins and minerals in smaller amounts.

While this sea bass is not the best example (although still relatively solid), fish tends to be high in vitamins and minerals.

This is generally good when you are trying to lose weight and get healthier.

Do keep in mind that it is possible to overdo it with certain nutrients.

For example, there are certain fish with a lot of selenium which can have negative side effects in large portions (6, 7).

It is not that likely you will reach this level with sea bass alone.

However, if you already eat a lot of brazil nuts, it may be smart to measure out your portions.

Do keep an eye on your mercury intake

Something else to keep in mind when eating fish is mercury.

Eating enough of this substance can cause 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 examples of fish high in mercury include (8):

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

Keep in mind that these are not the only types of fish that have mercury in them.

You typically want to check the recommendations to make sure you don’t eat too much of certain fish types during the week.

Does fish help you lose weight?

By now it should be clear that fish tends to be reasonably low in calories, high in protein, and high in vitamins and minerals.

The result is that eating more fish will typically make you feel a lot fuller and help you reach your ideal daily protein intake.

In turn, it will be easier to eat less of foods that are worse for weight loss.

At the same time, it is important to note that just eating more fish while keeping everything else the same will likely not make you hit your weight loss goals.

In simpler words, while fish will likely help you lose weight, the rest of your diet and lifestyle habits still play a role too.

You also don’t want to forget to keep an eye on your portion sizes of fish high in mercury and/or selenium.

Fish with vegetables to lose weight

Relevant weight loss studies

There are a few relevant studies that try to see the weight loss benefits of fish in action.

One study compared the effectiveness of different portion sizes of cod in calorie-restricted diets over an 8-week period.

Three groups of participants received the same dietary macronutrient (protein, fats, carbohydrates) composition.

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

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

A second small study found that the participants spontaneously 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?

As you can expect, the ideal amount of fish to eat will vary from person to person.

For example, the rest of your diet and your body weight will influence the recommendations a lot.

Additionally, different types of fish have different upper limit recommendations due to details like mercury content.

While keeping these things in mind, you may still like to know that the 2015-2020 Dietary Guidelines for Americans recommends the following amounts of fish (12):

  • At least 8 ounces (227 grams) of seafood (less for young children) per week based on a 2,000-calorie diet
  • For women who are pregnant or breastfeeding 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 still very general guidelines.

Ideally, you want to get personal guidance from an expert for more precise recommendations.

How to cook fish for weight loss

While “regular” fish tends to be good for weight loss, there are also a few ways to cook this food that are not as optimal for this goal either.

More specifically, some of the best ways to cook fish for weight loss are boiling, baking, grilling, and pan-frying it.

After/during that, you can also combine it with other healthy ingredients like vegetables, spices, herbs, and water (for fish soup of course).

On the other side, you generally don’t want to cook fish in ways like deep-frying or dishes like fish & chips and fish tacos when trying to lose weight.

Related posts:


Is fish good for losing belly fat?

While fish will not target this area specifically, it is one of the best food groups for losing belly fat.

Can I eat fish every day to lose weight?

As long as they avoid the fish high in mercury and don’t overdo it with selenium, many people can eat fish every day to lose weight.

Can I lose weight by eating fish and vegetables?

While you likely want to implement other types of food too, you could theoretically lose weight by eating fish and vegetables.

Photo of author


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.