How Much Fish Oil for Weight Loss?

Fish oil is not necessarily a magic weight loss pill.
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Fish oil benefits may include a sharper brain and better cardiovascular health. The connection between this supplement and weight loss is controversial, though. Rather than depending on fish oil pills to help you lose weight, you're better off eating a healthy diet and getting more exercise.



Fish oil is not necessarily a magic weight loss pill. The connection between this supplement and weight loss is tenuous at best, as studies that connect the two have been small or have only involved animal subjects.

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Why Take Fish Oil Pills?

Fish oil pills are supplements that contain two sources of omega-3 fatty acids, called docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), according to the Mayo Clinic. These healthy fats also occur naturally in fish and shellfish, including salmon, trout, mackerel, mussels, oysters and crab.

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Fish oil pills are often taken to reduce the risk of heart attacks and strokes. They come in liquid, capsule and pill form. These supplements may also help with high triglycerides, elevated blood pressure and rheumatoid arthritis. Furthermore, fish oil contains almost no mercury, which may be a cause for concern in some types of fish.

The Mayo Clinic recommends getting these nutrients from food, not supplements. While fish oil is generally safe, too much of it in supplement form may increase bleeding and interfere with anticoagulant drugs. When used in large doses, these products may suppress your immune system. If you do take fish oil supplements, it's best to use them under the guidance of a doctor.

Read more:Fish Oil Dosage for Adults


Fish Oil and Weight Loss

A small study conducted on 26 healthy Canadian men in their 20s and published in the February 2017 edition of the journal ​PLOS One,​ found that taking fish oil supplements for 12 weeks resulted in no change in metabolism rates at rest and during exercise. A faster metabolic rate means that your body is burning more calories. The only variation they found was a seasonal difference in fat burning rates. Men tended to oxidize fat better in cold temperatures.


The researchers stated that previous studies on fish oil supplements and metabolism rates have shown mixed results. Future studies with better protocols are needed, the authors said.

Another study, which appeared in the December 2015 issue of ​Scientific Reports​, looked the effects of fish oil given to mice. The mice fed fish oil gained less weight than those on a standard diet. They also had more energy and better fasting glucose and insulin levels than the mice in the control group.


However, the human study is quite small, and the study on mice is just that – a study of mice. Another review, which was published in the November 2015 issue of ​PLOS One,​ reports that the effects of fish oil on weight loss remain inconsistent in human studies.


The takeaway from this research paper is that there is no precise anti-obesity role for fish oil. The authors did, however, suggest that people with obesity may benefit from using fish oil supplements, along with other lifestyle changes. More studies are needed to confirm their efficacy.


Read more:4 Benefits of Fish Oil Supplements — and 3 Risks You Should Know About

Part of a Healthy Diet

While fish oil supplements may or may not be beneficial, fish oil does have a role in a healthy diet, especially if it comes from food, according to Harvard Health. That's because it's rich in omega-3 fatty acids, especially DHA and EPA. Fatty fish like salmon, mackerel and sardines are packed with these essential fatty acids.


Plants, like nuts, flax seeds and pumpkin seeds, are rich in another type of omega-3 fatty acid, alpha-linolenic acid, which your body can convert to DHA and EPA. What your body can't do, however, is make DHA and EPA on its own.

These essential acids are necessary for things like brain functioning and normal growth and development, and they may also help lower inflammation. Reducing inflammation in the body leads to better overall health. As the article in Harvard Health states, however, taking high doses doesn't necessarily give you that better health or aid in disease prevention.


Fish oil supplements are easy to take and convenient. The health benefits from fish oil are one reason Americans spend more than $1 billion a year on over-the-counter fish oil. It is also being added to other foods. But the benefits are questionable, the article reports.

A study of nearly 26,000 people in the January 2019 issue of the ​New England Journal of Medicine​ found that people who took fish oil supplements did not have lower rates of heart problems or cancer than those taking a placebo.


As Harvard Health notes, these supplements appear to be particularly beneficial for those don't eat fish. The article also reports that diets high in fatty fish or fish oil supplements may offer some protection against some types of cancer.

Fish, Health and Weight Loss

While the current evidence on the benefits of fish oil supplements for weight loss is mixed, some studies show that eating fish and seafood helps improve your health. A review featured in the May 2012 issue of Global Journal of Health Sciences found that people who eat diets high in seafood are healthier than those who don't.

Researchers concluded that individuals who eat more seafood as well as bioactive components derived from seafood have lower rates of heart disease and type II diabetes. They also stated that seafood helps with infant and child brain and vision development.

The general recommendation is to eat about two servings of fish per week. If you already do that, you may not need fish oil or omega-3s supplements.

Following a Mediterranean-style diet, which includes lots of fish, appears to be a plus in weight loss, according to an article on food and diet published by the Harvard T.H. Chan School of Public Health. Although definitions of a Mediterranean diet can be fuzzy, people who eat a diet high in fish, poultry, nuts and beans tend to gain less weight over the years than those following a diet high in red meat.

The Centers for Disease Control and Prevention also weighed in on the topic of eating fish. To lose weight, the CDC suggests replacing higher-calorie foods with foods are lower in calories but make you feel full. Fish, along with lean meat and poultry, increase satiety while taking in fewer calories.

Read more:The 10 Best Supplements


Consult a Health Care Provider

Fish oil supplements are considered to be an effective treatment for people with high levels of triglycerides in their blood. However, you should still follow your doctor's recommendations, Harvard Health states. Don't use these products without first making sure that they're safe for you.

If you're already taking fish oil supplements on your own, for weight loss or health, with no recommendation from a health care provider, you're probably better off having a conversation with your doctor, who can recommend the right dosage for your needs. The experts at Harvard state that the health benefits from fatty fish may come not just from the fats in fish, but also the vitamins, minerals and supporting molecules contained in the fish.

The Mayo Clinic cautions that fish oil supplements may not be safe for people with fish or shellfish allergies. Fish oil supplements may cause unpleasant side effects as well, including:

  • A fishy aftertaste
  • Bad breath
  • Indigestion
  • Nausea
  • Loose stools
  • Rash

Heart Failure and Fish Oil

Fish oil supplements have also been linked to improved cardiovascular health, but again, the research is mixed. The American Heart Association stated in 2017 that if you have heart failure or have recently had a heart attack, fish oil supplements may help. However, these pills don't prevent heart disease.

The studies on fish oil supplements are conflicting, according to the AHA. The mixed results extend to those who have suffered heart failure or a heart attack. While omega-3 fish oil supplements will not prevent a second heart attack, taking 1 gram a day may reduce deaths from coronary heart disease and sudden cardiac death by about 10 percent.

Those with heart failure, which occurs when the heart can't pump enough blood to the body, may benefit from fish oil supplements. The benefit, however, isn't clear. The AHA states that there's no harm in taking the supplements. One reason fish oil supplements may not be as effective as they once were is that now there are other treatments available to heart patients, which gives them more options.


Omega-3 Fatty Acids

Fish oil pills are made with oils derived from seafood sources. This oil is high in omega-3 fatty acids. These fats are essential fats, which means they are essential to the survival of human beings, according to the National Institutes of Health. This fatty acid is not produced in the body, so you need to obtain it from food.

Omega-3s are found naturally in some foods. Fatty fish, nuts and seeds are excellent sources. Plant oils, including flaxseed oil, canola oil and soybean oil contain large doses of omega-3s as well. You can also get these fatty acids from fortified foods, such as eggs, soy milk, fortified cow's milk and some juices.

These fats help your cells function properly, according to the Harvard T.H. Chan School of Public Health. They also jump-start your body into making hormones that regulate inflammation, blood clotting and the contraction and relaxing of the artery walls in your heart. Omega-3s also bind to receptors in the cells that regulate genetic function.

These fatty acids may play an important role in disease prevention, as the National Institutes of Health points out. People who eat seafood have a lower risk of several chronic diseases. It's not clear whether the benefits come from seafood itself or the omega-3s in food. That's one of the reasons why the research on fish oil supplementation is mixed.