Omega-3 Fish Oil: The Truth About Weight Loss | Signos

Fish oil supplements are touted for their health benefits, including lower cholesterol and better brain health. But can this ‘liquid gold’ supplement help with metabolism and weight management?

omega-3 fish oil supplements spilling out of a brown glass jar
Julia Zakrzewski, RD
— Signos
Health & Nutrition Writer
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Updated by

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Science-based and reviewed

May 17, 2024
July 21, 2022
— Updated:
July 22, 2022

Table of Contents

What Is Fish Oil? 

Fish oil comes from several different types of naturally fatty fish, including salmon, tuna, herring and mackerel. Their oils are full of healthy fats, which are a popular source of omega-3-fatty acids. Fish oil supplements are a great alternative for people who want the health benefits of fish without eating it. 

Cod liver oil is documented to have been used in medicine since the 20th century.1 Physicians at the time applied cod oil to help wounds heal, or instructed patients to drink the oil to help with tuberculosis and joint and muscle pain. 

Modern-day clinical trials have since proven various health benefits of the omega-3 polyunsaturated fatty acids found in fish oil.2 You can get your omega-3s through diet or you can opt for one of many available supplement formulas on the market. 

What Are Omega-3 Fatty Acids?

Omega-3-fatty acids are a class of fats that have been associated with numerous health benefits. Omega-3 fats are a type of polyunsaturated fatty acid (PUFA - a healthy fat). It’s essential to get omega-3s through diet or supplements, because your body can’t synthesize them.3

Omega-3 fatty acids occur naturally in different forms: alpha-linoleic acid (ALA), and eicosapentaenoic acid (EPA), which is converted into docosahexaenoic acid (DHA). 

EPA and DHA omega-3 fatty acids are proven to positively impact your health more than ALA. Fortunately, your body is the most efficient at absorbing EPA and DHA forms of omega-3. 

A study review observed that healthy young women were able to successfully convert 21% of ALA into EPA, and 9% of DHA. Young men in the study had lower conversion rates: 8% for EPA and 0-4% for DHA.3
These findings suggest that men may need to be more selective regarding their omega-3 food sources, and choose options that will be most easily absorbed. 

<p class="pro-tip"><strong>Learn more about</strong><a href="/blog/foods-to-avoid-for-weight-loss"> which foods to avoid if you want to lose weight</a></p>

Does Fish Oil Have Weight Loss Benefits?

The scientific community does not currently have strong evidence that fish oil will directly help with weight loss.5 Some animal studies have shown promising results, but these studies are difficult to translate to humans due to the amounts of EPA and DHA administered.6

However, there have been human studies investigating whether fish oil can indirectly support weight loss by affecting appetite and metabolism:


Fish Oil and Satiety 

Dietary fats, including omega-3 PUFA, are energy-dense and satisfying. Researchers theorize that meals with healthy fats will leave you satisfied and so you’re less likely to eat extra calories later on. 

A small-scale randomized control trial from 2008 measured the satiety of participants after eating a meal that included omega-3 fatty acids.7 Individual responses within the group indicated that participants still felt satisfied two hours after eating.

In a different study conducted in 2013, researchers discovered that supplementing fish oil with meals resulted in an increase in appetite, which was surprising considering the results from previous trials.8

Researchers concluded that more in-depth research is required to understand if omega-3 fatty acids from fish oil can improve weight loss results by increasing satiety. 

<p class="pro-tip"><strong>Learn more about</strong><a href="/blog/signs-of-hunger"> hunger signals and recognizing true hunger</a></p>

Fish Oil and Metabolism 

Metabolism is the furnace of your body, converting fuel (calories) into energy. 

Weight gain is commonly associated with a “slow” metabolism. Many weight loss programs and food supplements within the diet industry claim to help speed metabolism, but do not have the data to back these claims. Unfortunately, fish oil falls into this category. 

A study from 2010 compared the resting metabolic rate of 47 participants who either ingested sunflower oil or fish oil. After six weeks, the fish oil group did not show any change in metabolic rate.9

Another study from 2014 confirmed similar findings. One group of recreationally active men received a supplement with 3g of fish oil, while others received olive oil. A few members of the fish oil group showed an increase in resting metabolic rate, but the results were so small that researchers did not find them to be statistically significant.10

<p class="pro-tip"><strong>Learn about</strong><a href="/blog/metabolic-flexibility"> metabolic flexibility and why you want it</a></p>

underwater view of woman swimming laps in a pool
While there’s no data to support claims of boosting metabolism, fish oil has other scientifically proven benefits.

Proven Health Benefits Of Fish Oil

While studies on fish oil for weight loss have shown no effect, fish oil has been linked to several other important health benefits:

Fish Oil Can Improve Cholesterol Levels

It is generally accepted that omega-3 fatty acids can improve cholesterol levels. Polyunsaturated fats have been shown to lower triglycerides, a type of fat in the blood that is linked to heart disease.11

While the data on omega-3 consumption and heart health consistently concludes that omega-3 PUFA may play a helpful role, fish oil alone is not enough for long-lasting cardiovascular health. You also need to follow a high-fiber diet rich in produce, keep your alcohol intake low, and stay physically active. 

<p class="pro-tip"><strong>Learn about</strong><a href="/blog/mediterranean-diet"> PUFA in the Mediterranean Diet</a></p>

Fish Oil Supports Brain Health

Omega-3 fatty acids may protect the brain from deterioration. As the North American population ages, this area of study is becoming increasingly prioritized. 

A 2018 review of 25 randomized controlled trials indicates there is some positive correlation between adequate omega-3 intake and brain health.12 Other factors that support brain health include following a regular sleep cycle, staying active, and being social! 

Fish Oil Promotes Wound Healing

Omega-3 fatty acids promote faster-wound healing and decrease risk of infection.13 This is especially relevant for anyone undergoing surgery, and people with chronic wounds.  

Fish Oil Can Reduce Inflammation 

Inflammatory markers flood the body during times of sickness or injury. Some signs of inflammation can be silent, but more commonly they add to your discomfort when you feel unwell. Omega-3 fatty acids have anti-inflammatory properties and can reduce the inflammatory response.14

People who suffer from chronic inflammation in the joints, such as arthritis, prioritize the inclusion of omega-3 rich foods in their diet.15 A specialist may recommend an omega-3 supplement if warranted, but they will encourage you to focus on food sources

The ability to stay mobile and pain-free significantly improves quality of life, and may increase the chances of meeting weight loss goals. 

Food Sources of Omega-3 Fatty Acids

ALA variations of omega-3 are most abundant in plant sources, while EPA and DHA are found more in animal sources.4 EPA and DHA omega-3s are more readily absorbed by the body, compared to ALA. Your body can convert ALA into EPA and DHA, but not as efficiently, which can make it more challenging (but not impossible) to meet your omega-3 intake goals. 

Plant sources of ALA omega-3 include: 

  • Walnuts 
  • Chia seeds
  • Soybean 
  • Flax seeds
  • Hemp seeds
  • Wheat germ

Animal sources of EPA and DHA omega-3 include: 

  • Trout
  • Salmon 
  • Herring 
  • Mackerel 
  • Black Cod 
  • Sardines

Omega-3s are found in a variety of food sources, including seaweed (a rare plant source of both EPA and DHA), kidney beans, edamame and many others. There are also many foods and beverages fortified with omega-3s. This is great news for vegetarians, or for people who simply don’t like fish! 

female hands preparing whole fish with lemon slices and herbs before baking
In addition to omega-3 fatty acids, fish has important nutrients like vitamin D & B2, iron, zinc and potassium.

Is it Better to Get Omega-3s from Fish or a Supplement? 

There is no evidence to say that food sources of omega-3 are better for your health compared to fish oil supplements. A golden rule to health behavior modification is to adopt a change in your lifestyle or diet that can be consistently repeated. 

Signs you may be better off with an omega-3 supplement include:

  • You don’t eat fish 
  • The cost of fish is outside your budget 
  • You like fish, but meal planning is not your strength, so you forget to eat fish regularly 
  • Your family doesn’t like the smell of fish, and you don’t want to prepare it for one

There are many fish oil products and omega-3 supplements on the market, including vegan-friendly options. Try to buy a product that has an EPA/DHA blend because these forms of omega-3 will have the greatest impact on your overall health. 

How Much Fish Oil Is Enough? 

The American Heart Association recommends two servings of fatty fish per week to meet your omega-3 needs.3 To optimize the meal, prepare your fish using lean cooking methods such as broiling, barbecuing, or sautéeing. If you need inspiration on how to get started, check out this delicious Signos recipe for salmon and broccoli with pumpkin seed pesto. 

Other popular fish such as tilapia, tuna, and haddock offer trace amounts of omega-3s. Although they are a lean and healthful protein option, you should not rely on them to meet your omega-3 requirements. 

<p class="pro-tip"><strong>Learn about</strong><a href="/blog/protein-for-weight-loss"> protein and weight loss</a></p>

Supplement Dosage 

Most fish oil supplements are sold in capsules containing 1000mg. As of 2022, the FDA suggests keeping your intake between 2000-3000mg.16

Some omega-3 supplements are sold in liquid form. You will need to follow the directions to ensure you are using it safely and correctly. A liquid supplement can be helpful for people who can not swallow the gel capsules, which tend to be on the larger side as far as supplements go. 

Can I Eat Fish and Take a Fish Oil Supplement? 

As mentioned above, the FDA recommends keeping your total omega-3 intake between 2000-3000mg per day. If you go over this limit you may decrease your immune function or experience gastrointestinal bleeding. 

Although omega-3 is healthful, more of it is not necessarily a good thing. Follow the guidelines and you will be safe. 

The Dreaded Fish Burps 

Fish burps can be a barrier to staying consistent with your omega-3 supplement routine. About twenty to thirty minutes after you ingest the capsule, you may notice a fishy flavor on your breath. This happens because the capsule is starting to break down in your stomach, releasing the oil. 

Freezing your fish oil pills can help. Keeping your supplements in the freezer will not affect the quality of the product, and it ensures the capsule will start to dissolve further down your digestive tract. 


There is no scientific literature that confirms fish oil or fish oil supplements will help with weight loss. If you want to lose weight, you should focus your efforts on healthy and sustainable diet changes and regular exercise. 

<p class="pro-tip"><strong>Learn about</strong><a href="/blog/sustainable-weight-loss"> the benefits of sustainable weight loss</a></p>

Fish oil can help you stay healthy and maintain quality of life. Omega-3s can lower cholesterol levels and protect your brain as you age. 

It is up to you to decide if you want to get your omega-3s through food sources or a supplement. Both options are acceptable, but you need to pick a method that will allow you to be consistent with your intake. 

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Topics discussed in this article:


  1. Griffing G. T. (2008). Mother was right about cod liver oil. Medscape journal of medicine, 10(1), 8.,aching%20joints%2C%20and%20stiff%20muscles
  2. Shahidi, F., & Ambigaipalan, P. (2018). Omega-3 Polyunsaturated Fatty Acids and Their Health Benefits. Annual Review of Food Science and Technology, 9(1), 345–381. 
  3. Hutchins, H. (2005). Symposium Highlights - Omega-3 Fatty Acids: Recommendations for Therapeutics and Prevention. Medscape. 
  4. American Heart Association. (2021, November 1). Fish and Omega-3 Fatty Acids. Www.Heart.Org. Retrieved June 2022, from,in%20omega%2D3%20fatty%20acids
  5. Du, S., Jin, J., Fang, W., & Su, Q. (2015). Does Fish Oil Have an Anti-Obesity Effect in Overweight/Obese Adults? A Meta-Analysis of Randomized Controlled Trials. PLOS ONE, 10(11), e0142652. 
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  7. Parra, D., Ramel, A., Bandarra, N., Kiely, M., Martínez, J. A., & Thorsdottir, I. (2008). A diet rich in long chain omega-3 fatty acids modulates satiety in overweight and obese volunteers during weight loss. Appetite, 51(3), 676–680. 
  8. Damsbo-Svendsen, S., Rønsholdt, M. D., & Lauritzen, L. (2013). Fish oil-supplementation increases appetite in healthy adults. A randomized controlled cross-over trial. Appetite, 66, 62–66. 
  9. Noreen, E. E., Sass, M. J., Crowe, M. L., Pabon, V. A., Brandauer, J., & Averill, L. K. (2010). Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. Journal of the International Society of Sports Nutrition, 7(1). 
  10. Gerling, C. J., Whitfield, J., Mukai, K., & Spriet, L. L. (2014). Variable effects of 12 weeks of omega-3 supplementation on resting skeletal muscle metabolism. Applied Physiology, Nutrition, and Metabolism, 39(9), 1083–1091. 
  11. Handelsman, Y., & Shapiro, M. D. (2017). Triglycerides, Atherosclerosis, and Cardiovascular Outcome Studies: Focus on Omega-3 Fatty Acids. Endocrine Practice, 23(1), 100–112. 
  12. Derbyshire, E. (2018). Brain Health across the Lifespan: A Systematic Review on the Role of Omega-3 Fatty Acid Supplements. Nutrients, 10(8), 1094. 
  13. Alexander, J. W., & Supp, D. M. (2014). Role of Arginine and Omega-3 Fatty Acids in Wound Healing and Infection. Advances in Wound Care, 3(11), 682–690. 
  14. Wall, R., Ross, R. P., Fitzgerald, G. F., & Stanton, C. (2010). Fatty acids from fish: the anti-inflammatory potential of long-chain omega-3 fatty acids. Nutrition Reviews, 68(5), 280–289. 
  15. Kostoglou-Athanassiou, I., Athanassiou, L., & Athanassiou, P. (2020). The Effect of Omega-3 Fatty Acids on Rheumatoid Arthritis. Mediterranean Journal of Rheumatology, 31(2), 190. 
  16. Krupa K, Fritz K, Parmar M. Omega-3 Fatty Acids. [Updated 2022 May 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: 

About the author

Julia Zakrzewski is a Registered Dietitian and nutrition writer. She has a background in primary care, clinical nutrition, and nutrition education. She has been practicing dietetics for four years.

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