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Essay On Brown Fat

There have beenhypedreportsoflateabout “brown fat”. Different from the fat we mostly have (white fat), brown fat is capable of burning more energy. So the theory goes: if we have more brown fat, we can lose weight. But selective reporting and misinformation has blurred the lines between fact and fiction.

What is brown fat?

Grab that roll of fat on your stomach – that is white fat. The job of white fat is mainly to store energy, and then release it when other organs need it. We have much less brown fat which is hidden deep in the torso and neck. The main role of brown fat is to heat our body when we’re cold. To produce heat, brown fat cells expend (burn) energy.

Decades of research, mainly in rats and mice, tell us when brown fat is “activated” from its resting state (for example, by cold exposure) it can burn a lot of energy relative to its small size. The potential for health lies in whether this energy-burning power can be harnessed to treat obesity.


Read more: Eight diet myths – busted!


Brown fat’s presence in adult humans has been known for decades. While previously believed to have no function, in 2009 a series of studies showed it does burn energy when activated by short-term (minutes/hours) cold exposure. Our brown fat can’t burn as much energy as the brown fat in mice, and some evidence suggests its normal energy burning level is so low as to be irrelevant.

When brown fat is not “activated”, its energy expenditure is very low. The level of cold exposure and the amount of the skin surface exposed control the amount of energy expenditure. Most importantly, “training” brown fat forces it to become better at burning energy. But training involves weeks of daily cold exposure for several hours – something we modern humans rarely, or ever, do.

Can cold showers activate brown fat?

This new awareness of brown fat has, unsurprisingly, led to exaggeration of its purpose, function and benefits in humans. Cold exposure as a health fad has boosted this recent popularity. Common recommendations to activate brown fat are cold showers and (worryingly), immersion for short periods in very cold (below -100°C) nitrogen gas.

Brown fat, like muscle, follows a “use-it-or-lose-it” principle and, as highlighted above, the more you use it the better it gets. Training brown fat requires cold exposure for several hours per day. So brief periods such as a few minutes in the shower or a dip in nitrogen gas interspersed in an otherwise warm lifestyle are unlikely to train brown fat in a meaningful way.


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Should strong-willed devotees be willing to participate in hours of daily cold exposure, they will most likely increase their brown fat’s energy burning ability. But weight loss is unlikely to follow. Remember, the main function of brown fat is to keep you alive, not thin. During cold exposure, hunger is stimulated alongside brown fat activation to ensure there is adequate fuel for the fire.

What about exercise?

Recentstudies in mice show a role for regular exercise in the “browning” of fat (making white and brown fat become more brown). These studies suggest exercising muscles release hormones that make brown and white fat cells become more “brown-like”, meaning the fat cells can burn energy when activated by cold (noting that exercise itself does not activate brown fat).

But media hyperbole ignored current best evidence from exercise training studies in humans that show the opposite – cold-stimulated brown fat energy expenditure is reduced.

And contrary to recentreports, exercising in the cold will not allow you to get fit and increase brown fat function at the same time.

Nutrition supplements and medications

Despite the promotion of supplements to increase brown fat development, there are currently no medications or supplements proven to increase brown fat in humans. Some evidence suggests extracts from capsinoid-containing plants (such as chilli peppers) activate brown fat, but these have never been directly shown to increase human brown fat energy burning.


Read more: How we can change our body shape with exercise


Our research also shows twodrugs that we and others thought would increase brown fat function, based on previous studies in mice and rats, actually decreased it.

The future: brown fat in disease prevention?

Understanding the role and relevance of brown fat for our health is at an early stage, and we have yet to discover its full capability. Being cold most of the time, for a really long time, will increase brown fat function, but there is currently no evidence for more suitable options, particularly ones that don’t also stimulate hunger.

We also don’t know whether brown fat activation directly improves health. Here the strongest evidence is that its function is reduced in obese people. But whether this is either cause or effect, and whether brown fat activation might reverse obesity remains unknown. Clearly there’s a need for more human research to uncover the facts.

iStock/UberImagesUnlike white fat—which makes up the vast majority of the fat in our bodies and is used to store any excess calories we consume—brown fat actually burns calories to produce heat (under the right conditions). In fact, when fully activated, brown fat generates three hundred times more heat than any other tissue in the body. Just two ounces of brown fat appear capable of burning several hundred calories per day—the equivalent of a 30-minute bout of exercise. Most, and perhaps all, adults, have small pockets of brown fat.

Brown fat is typically located in the sides of the neck—sometimes running down into the shoulder and upper arms—and in the region just above the collarbone. Other common locations include the upper back between the shoulder blades and along the sides of the upper spine. The amount of brown fat generally adds up to couple of ounces at most. Because they are so small and lie deep under the skin, they don’t appear as bulges, like love handles.

2. Cold temperatures activate brown fat

In one study, Swedish researchers scanned five subjects after they’d spent two hours at temperatures ranging from 63°F to 66°F. During the scan itself, the subjects cooled their body temperature even further by repeatedly placing one foot in ice water for five minutes at a time, followed by five minutes out of the water. The investigators found not only that all the subjects had detectable brown fat deposits, but that the added exposure to the cold ice water boosted their brown-fat activity 15-fold.

3. Brown fat improves your blood sugar metabolism

Brown fat may have unique diabetes-fighting properties: People with lower glucose levels tend to have more brown fat than those with higher levels, which indicates that it may play a direct role in glucose control. One group of investigators, for example, recently found that a certain protein in brown fat appears to enhance the metabolism of white fat. When they studied a strain of experimental mice who were lacking this protein, the mice expended less energy, gained weight, and developed diabetes.

In another study at Joslin Diabetes Center (where I am research director), a research team transplanted a small amount of brown fat from one group of mice into the abdomens of another group. The results were astonishing: After eight weeks, the mice given the transplants were not only leaner than a placebo group, but also processed blood glucose better and had reduced insulin resistance.

4. Brown fat can increase your metabolic set point

This set point is the level of body weight at which the brain automatically begins to slow metabolic activity, making it more difficult to lose additional weight. By revving metabolic activity, brown fat could help combat the metabolic slowdown that occurs when people start dieting. If someone is able to burn an extra 200 or 300 calories a day through their brown fat, that’s enough to shed a pound of body fat in just a couple of weeks. As Americans get older, we typically add 10 pounds of weight per decade. The calorie-burning boost from brown fat could be enough to reverse this weight gain and help older individuals maintain the body fat they had as young adults.

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5. To activate brown fat, expose your skin to cool temperatures

Cold temperatures send a signal to your brain, which then acts to stimulate brown fat activity in two ways: by acting on your vascular system directly to increase blood flow to your brown fat stores and by sending nerve impulses to brown fat cells that stimulate am additional boost in cellular activity. How cold do you have to be? Researchers have found that sitting in a 59°F room for two hours wearing summer clothing will stimulate brown fat to burn an extra 100 to 250 calories, depending on the individual. A Japanese research team found that half of subjects under age 38 showed signs of brown fat activation in a 66°F setting. (Results were less impressive for people older than 38). Lowering your home’s thermostat to the mid-60s or below may be enough to stimulate at least some brown fat activity.

6. Exercise in cool temps

Boost the amount of calories you burn during exercise by stimulating your brown fat stores during your workout. Exercise in temperatures that are 62°F to 64°F or lower. Even better: Make sure your skin is exposed because the evaporation of sweat as you exercise adds to the cooling effect. What you don’t want to do: Increase how much you perspire by turning up the heat when you exercise. This hotter environment will actually shut down brown fat activity.

7. Consider a low-fat, high-carb diet

Although there’s no firm evidence that any specific foods or nutrients can activate brown fat, it’s interesting to note that radiologists—who want to decrease brown fat activity when doing scans of cancer patients because the heat generated by activated brown fat makes it harder to see tumor-related activity—routinely recommend that patients eat a high-fat, low-carb diet before scans, on the grounds that this reduces brown fat activation. This suggests that a low-fat, high-carb diet (like the kind I recommend in my book The Diabetes Reset) will boost brown fat activity.

8. Eat more apples—with the peel on

Ursolic acid—a substance that occurs in high concentrations in apple peels—increases brown fat and muscle mass, while at the same time reducing obesity and improving glucose tolerance. Other foods that contain ursolic acid include cranberries, blueberries, plums, and prunes, as well as the herbs oregano, thyme, lavender, holy basil, bilberry, devil’s claw, peppermint leaves, periwinkle, and hawthorn. Animal studies have also found that the herb bitter melon appears to increase brown fact activity.

Avoid, Reverse, and Control Diabetes

In his new book The Diabetes Reset, George King, MD, research director and chief science officer at Harvard’s Joslin Diabetes Center, translates the latest cutting-edge research about nutrition, metabolism, and more into a diet and lifestyle plan to prevent and treat diabetes. Learn more and buy the book here.

More: Diet & Weight Loss, Everyday Wellness, Fitness, Healthy EatingAging Well, Diabetes

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