--- title: Here's How Fish Oil Makes Mice Lose Weight description: A new animal study finds that fish oil—omega 3 fatty acids—helps mice lose weight and creates more calorie-burning brown fat in the body canonical: https://time.com/4155477/fish-oil-omega-3-weight-loss/ author: Mandy Oaklander article:opinion: false article:content_tier: free article:published_time: 2015-12-21T16:11:20.000Z article:modified_time: 2026-08-04T07:56:47.083Z article:section: Health og:title: Fish Oil Causes Weight Loss In Mice: Study og:description: A new animal study finds that fish oil—omega 3 fatty acids—helps mice lose weight and creates more calorie-burning brown fat in the body og:url: https://time.com/4155477/fish-oil-omega-3-weight-loss/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltdf82d8abde596432/69887627bc6cfcb87e3daede/fish-oil-capsules.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 5616 og:image:height: 3159 og:image:alt: fish oil capsules og:type: article twitter:card: summary_large_image twitter:title: Fish Oil Causes Weight Loss In Mice: Study twitter:description: A new animal study finds that fish oil—omega 3 fatty acids—helps mice lose weight and creates more calorie-burning brown fat in the body twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltdf82d8abde596432/69887627bc6cfcb87e3daede/fish-oil-capsules.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # This Popular Supplement May Spur Weight Loss: Study > Sponsored content. 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Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-health-2026q3/newsletters?i=59fc4801-b8cd-4479-b0c8-bf73a3d2d311&cr=time-nl-health-2026q3-v1) ## Video: The Truth About Fat [Watch (HLS stream): The Truth About Fat](https://cdn.jwplayer.com/manifests/uYGhfNfS.m3u8) (5:15)  _Published 2014-06-12. When you want to lose weight or get healthy, what is the first thing you would normally cut from your diet? If you said fat, you're not alone_  by [Mandy Oaklander](https://time.com/author/mandy-oaklander/)  ## Mandy Oaklander Oaklander is a senior editor at TIME. Dec 21, 2015 4:11 PM UTC  Cod liver oil capsules Cod liver oil capsules Getty Images  by [Mandy Oaklander](https://time.com/author/mandy-oaklander/)  ## Mandy Oaklander Oaklander is a senior editor at TIME. Dec 21, 2015 4:11 PM UTC Many people take fish oil with the hopes of [boosting their brain function](http://time.com/3915030/boost-memory-exercise/), or alleviating depression, or reducing inflammation in the body. Some debate remains about the efficacy of fish oil supplements in producing these benefits in humans, but a new animal [study](http://www.nature.com/articles/srep18013) published in the journal _Scientific Reports_ finds that fish oil does appear to aid with weight loss—in mice. In the Japanese study, the researchers fed two groups of mice fatty food, but one group had fish oil added to the chow. Mice that ate this food gained significantly less weight and less fat, compared to the group with regular chow. They also and had lower insulin and fasting glucose levels, plus a hotter core temperature. The scientists then measured energy burn and found that the mice fed fish oil burned more calories—possibly due to an increase in [brown fat](http://time.com/4003974/gene-burns-fat/), a kind of fat that burns calories. Other research has shown an anti-obesity effect of fish oil, the researchers write. **MORE**: [How Bacteria And Brown Fat Can Spur Weight Loss](http://time.com/4148177/microbiome-microbes-brown-fat/) Cold temperatures activate brown fat, earlier research has shown. “Your hypothalamus detects that, which in turn activates the sympathetic nervous system,” explains Dr. Majid Fotuhi, medical director of NeuroGrow Brain Fitness Center in Virginia, who was not involved in the study. When that happens, brown fat cells get the signal to generate heat through the activation of a protein called UCP1. The scientists found higher levels of this particular protein, UCP1, in the mice who ate fish oil. They also found UCP1 in the white fat. Usually, Fotuhi says, white fat sits around in a useless mass, not doing much. But the white fat in mice who were fed fish oil contained high levels of the UCP1 protein—indicating that fish oil may help turn white fat into brown fat. **MORE**: [Eating Fish May Lower Your Risk For Depression](http://time.com/4030506/fish-omega3-depression/) The researchers discovered that fish oil works on the receptor that activates UCP1\. They verified these findings by knocking out that receptor in mice and feeding them fish oil; without the receptor, the mice didn’t lose weight or gain brown fat. “This provides scientific evidence that fish oil can activate brown adipose tissue to burn fat and help with weight loss,” Fotuhi says. What’s significant about the results, Fotuhi says, is that the researchers discovered the mechanism by which fish oil caused weight loss and brown fat production—at least in mice. Finding a drug that _does_ do the same thing in people, obviously, is the “golden target.” But the science isn’t there yet. “The results are preliminary, and I wouldn’t rush to buy a bottle of omega-3 fatty acids to lose weight,” Fotuhi says. (He does add, however, that doing so would likely confer brain benefits.) For now, consider it good news for mice who want to lose weight. As for humans, stay tuned. ## Transcript [ MUSIC ] There's something we all enjoy about staying for dinner. You ever thought why? What was on your dinner table when you were younger? Chances are it had a lot to do with, what your doctor was telling you is healthy. Building a strong healthy body is like building a strong, beautiful building. If the foundation is weak, the whole building will be weak. It takes five fingers to point the way to healthful eating habits. Well, here we go. For years, the government published dietary guidelines. Meant to keep Americans healthy. There's a great deal to learn. Tell me what you eat, and I'll tell you what you are. The body needs certain substances to live and grow. And remember, your body isn't just like an automobile. For years, the key measures of those guidelines were the same, cut fat from your diet. The committee's original report urged Americans to reduce their risk of heart attack. By reducing their intake of cholesterol down to the equivalent of about one egg a day. And those guidelines had an effect. From 1977 to 2012, per capita consumption of eggs fell by 9 %, beef by 37 %, whole milk by 72 %. Calories from saturated fat fell, while calories from supposedly safe carbohydrates increased. As one expert put it, it was a vast nutritional experiment. With nearly a million American's a year dropping dead from heart disease in the mid 80s, we had to try something. Nearly four decades later results are in. The experiment was a failure. Americans are sicker than they've ever been before. The prevalence of diabetes has gone up 157 % from 1980 to 2011. Nearly one in ten Americans now has the disease. Causing the public health system $ 245 billion a year. Heart disease is still the number one killer in the country. Americans are as obese as ever. So, what went wrong? Good old granola. Great for taste but loaded with fat. It doesn't take much of imagine a leap to assume that fat would make us fat, clog our arteries and raise the risk of heart disease. It turns out that saturated fat is a lot more complicated than we think. Carbohydrates and fats are nutrients. Like man, you need nutrients to live and grow. [ MUSIC ] Firstly, there are two kinds of cholesterol. LDL which is linked to heart disease and HDL which can be protective. Fats that course through the blood are known as triglycerides and high levels of those are linked to heart disease. Saturated fat raises LDL cholesterol but also raises HDL. Moving LDL buildup on arterial walls. So raising both, makes saturated fat a cardio wash. One key piece of information is that LDL seems to come in two forms. Large and fluffy, small and dense. Those smaller particles are linked to heart disease, while the larger ones are mostly benign. Saturated fat increases the number of large particles. The opposite happens with carbs. I don't get it. Researchers have long since discovered the kind of fats found in olives and in fish like salmon. Are actually heart protective. Now it turns out the fats found in meat and dairy, aren't as bad as we feared before. So that means by focusing so much on fats. We may actually have been making ourselves sicker. So, she brings up the subject of reduced- fat cheese. It's a fat- free [ UNKNOWN ]. Fat- free, cholesterol free. Low- fat granola. Reduced- fat Kettle chips. Reduced- fat Chips Ahoy. Lowfat cottage cheese. Non- fat yogurt is the perfect example. The thinking for consumers was simple. Fat was dangerous. This product had no fat. Therefore, it must be healthy. It's non- fat, which means less calories. [ MUSIC ] But amid the confusion about fat, we end up replacing it in our diets with sugars and carbohydrates, which meant our calorie intake was actually going up. When carbs and things like corn and white bread are ingested into your body, their converted into sugars. Those sugars convert to insulin cuz it's fat cells go into storage overdrive, leading to weight gain. Since fewer calories are then left to fill the body, you begin to feel hungry it means our metabolism begins to slow down in effort to save energy, we eat more and we gain more weight, never quite feeling full. As this process repeats, our cells become more resistant to insulin, which causes us to gain more weight, which increases insulin resistance in a vicious circle. Cut calories, and people just get hungrier. Obesity, diabetes, high triglycerides and low HDL cholesterol can all follow. Study after study has found it's very difficult to lose weight on a very low- fat diet. Possibly because fat and meat can produce a sense of satiety, that's hard to achieve with carbs, making it easier to simply stop eating. But it isn't just the increase in carbs that affects us. These processed, low saturated fat alternatives, come loaded with sugars, salt, preservatives, and even some unhealthy fats. So what's the real alternative? As one extra puts it, the cold hard truth about diet is that the only way to eat well, is to eat well. You'll be happier and you'll be healthier, if you focus on real whole foods, whether they have fat or not. Got it. 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