Does Fish Oil Speed Up Your Metabolism?

Fish oil supplements

Supplement use is on the rise as people look for ways to slow the aging process and stay healthy and functional throughout life. One of the most popular supplements is fish oil, an oily substance derived from the tissues of fatty fish, such as salmon, tuna, anchovies, and mackerel. Fish oil supplements are popular due to their omega-3 fatty acid content.

The main omega-3s in fish and fish oil supplements are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These omega-3s have modest anti-inflammatory activity due to their effects on substances called eicosanoids that moderate the body’s inflammatory pathways. The fish used to make fish oil don’t produce their own omega-3s but accumulate them in their tissues by feeding on microalgae and other sea life that have omega-3s. Larger fish tend to have higher quantities of omega-3s.

Can Fish Oil Supplements Speed Up Your Resting Metabolism?

Although it’s not the main reason most people take them, some research suggests that taking fish oil supplements boosts the resting metabolic rate. If that’s the case, you might expect that fish oil supplements would help with weight loss by increasing the rate at which your body burns energy. What does science say about the impact of fish oil on resting metabolic rate?

A few small studies suggest that fish oil supplements elevate resting metabolism. One study found that older female adults who took 3 grams of fish oil daily experienced an increase in resting metabolic rate of 14.0%. That’s a substantial bump! The fish oil ramped up resting metabolism both after exercise and at rest.

Another study found that taking 6 grams of fish oil daily for a similar length of time raised resting metabolism by 3.8%. However, this is a high dose of fish oil. Most sources don’t recommend taking more than 2 grams daily, except under the care of a doctor, as fish oil increases the risk of bleeding by interfering with blood clotting. Plus, despite fish oil’s anti-inflammatory benefits, research finds that it can be mildly pro-inflammatory at higher doses. Although variable, each gram of fish oil typically contains between200 milligrams and 500 milligrams of DHA and EPA.

Fish Oil and Weight Loss

Do these apparent boosts in metabolism help with weight loss? Another study published in the Journal of Internal Society of Sports Nutrition found that 6 weeks of supplementing with 4 grams daily of fish oil led to a 0.88 kilograms reduction in body fat and a 0.20-kilogram increase in lean body mass after 3 weeks, although this wasn’t considered significant. The participants didn’t reduce their calorie intake or restrict their diets.

Also noted among fish oil consumers in the study was a significant drop in cortisol in the saliva of the participants. Cortisol is a stress hormone linked with muscle loss and increases in belly fat, and this drop may explain some of the fat loss and muscle gain the participants experienced. Interestingly, guys who took the fish oil supplements enjoyed a reduction in waist circumference relative to the control group.

On the downside, not all studies show fish oil significantly boosts metabolic rate. Also of concern is that participants in these studies used more fish oil than what is currently recommended. Fish oil and omega-3s can interact with some medications and supplements. If you take a blood thinner, don’t take fish oil supplements without talking to your physician first.

Another Way Fish Oil May Help with Weight Loss

Some studies suggest that consuming fish oil reduces appetite and boosts satiety, although not all studies have reached this conclusion. As far as weight loss, a 2015 study found that fish oil supplementation didn’t boost weight loss when participants followed a calorie-restricted diet. However, those who took the fish oil lost more belly fat, leading to a healthier waist-to-hip ratio.

Fish Oil for Heart Health

Most people take fish oil supplements for the potential heart health benefits. Some studies show that the EPA and DHA in fish oil supplements lower blood pressure, reduce triglycerides, decrease inflammation, and lower the risk of sudden death, although more recent studies suggest the benefits may be overstated. Some studies show little or no heart health benefits from taking fish oil. But whether fish oil is beneficial may depend on whether you already eat fish. Some research suggests that if people don’t eat at least 1.5 servings of fish weekly, taking fish oil supplements may reduce the risk of heart attacks. Research also suggests that fish oil may be beneficial for people with heart failure and those recovering from a heart attack. The question is whether taking a fish oil supplement lowers the risk of heart disease in healthy people who already eat fish regularly.

Why Not Just Eat Fish?

Eating fatty fish twice per week provides enough EPA and DHA to offer potential heart health benefits. Plus, you get the added protein and other vitamins and minerals in fish. However, fish, especially large fish higher on the food chain, are increasingly contaminated with heavy metals and other environmental pollutants, such as dioxins, mercury, and PCBs, that may, over time, harm health. Fish oil supplements may also contain heavy metals and other contaminants, although manufacturers of higher quality supplements use molecular distillation to remove these contaminants.

If you eat fish, stick to smaller fish and those lower on the food chain. Good choices are wild-caught salmon, pollock and canned light tuna. Some fish contain such high levels of mercury that you should avoid them entirely. These include king Mackerel, tilefish, shar, and swordfish.

The Bottom Line

Fish oil supplements may modestly boost resting metabolic rate, although not all studies agree. However, you need to consume a fair amount to get this benefit. In contrast, you can get the potential heart health benefits by consuming only 2 grams of fish oil daily or eating fish twice per week. Fish is a good source of protein and contains vitamins and minerals you don’t get from taking a fish oil supplement. Either way, research fish oil supplements before taking one and talk to your physician beforehand. If you eat fish, choose smaller fish that are high in omega-3s and low in contaminants, usually those lower on the food chain.



·        Appl Physiol Nutr Metab. 2014 Sep;39(9):1083-91. doi: 10.1139/apnm-2014-0049. Epub 2014 Apr 23.

·        J Int Soc Sports Nutr. 2010; 7: 31.

·        PLoS One. 2015; 10(11): e0142652.

·        Appetite. 2008 Nov;51(3):676-80. doi: 10.1016/j.appet.2008.06.003. Epub 2008 Jun 14.


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