The Science of Brown Fat
Enhancing glucose metabolism and fighting diabetes.
Posted Oct 26, 2016
The calorie-burning potential of brown fat is exciting in and of itself, particularly because losing weight is so important for people with type 2 diabetes. But brown fat may have other diabetes-fighting properties as well: People with lower glucose levels tend to have more brown fat than those with higher levels, indicating that it may play a more 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 research project, conducted here at Joslin in Dr. Laurie Goodyear’s section on Integrative Physiology and Metabolism, a team headed by Dr. Kristin Stanford transplanted a small amount of brown fat from one group of mice into the abdomens of another group. The results of the study 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. In a subsequent experiment, mice with brown fat transplants who were put on a high-fat diet had less weight gain and better glucose control than a placebo group. Further testing showed that the mice in the transplant group had elevated levels of various proteins and other substances that are important for blood glucose control.
Equally intriguing is the possibility that we may be able to grow additional brown fat cells in our body. In another groundbreaking piece of research, a team of basic scientists at Joslin led by Dr. Yu-Hua Tseng identified the adult stem cells that turn into brown fat and developed a way to extract these progenitor cells from both white fat and muscle tissue and coax them to grow into brown fat cells. Drs. Tseng and Cypess have also joined forces to begin teasing out the molecular pathways that are involved in the growth of brown fat cells. Researchers are also studying beige fat, which differs slightly from brown fat in its physiology but burns calories almost as effectively as brown fat does.
All of this innovative brown and beige fat research being conducted at Joslin and elsewhere means that we’re certain to be hearing more news about this fascinating tissue in the years ahead. In fact, I think there’s a reasonable chance that some form of personalized brown fat therapy may emerge at some point in the future, at least for those able to afford it. In the meantime, though, we already know enough to suggest some very inexpensive ways for you to maximize the activity of your own brown fat. In the next section, I’ll explain how to do this.
How to Increase Your Own Brown Fat Activity
Although some people have dismissed brown fat as a biological novelty, I believe its promise as an important tool for fighting type 2 diabetes and obesity is very real. If someone is able to burn an extra two or three hundred calories per day, that’s enough to shed a pound of body fat in just a couple of weeks. As Americans get older, we typically add ten 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 weight they had as young adults. By revving up metabolic activity, brown fat could also help combat the metabolic slowdown that occurs when people start dieting—the set point phenomenon described previously, which is one of the most difficult obstacles to losing weight.
Activating your brown fat is probably not going to bring someone from an obese state to a healthy body weight on its own, but if brown fat activation is combined with exercise and diet, it could make a major difference in terms of helping the one fourth of the U.S. population who are significantly overweight drop down to a normal, healthy weight.
One thing that’s clear from studies done so far, though, is that you have to find a way to trigger activity in your brown fat cells in order to experience their calorie-burning effect. On the other hand, as Dr. Cypess has shown in his cool-vest experiments, under the right conditions, activation of your brown fat can occur very quickly. Here are some suggested ways to stimulate your own brown fat cells to begin burning calories. As always, I want to stress that everyone’s physiology is slightly different and that some of these approaches may work better for you than others.
Expose Your Skin to Cooler Temperatures
The most proven way to activate brown fat is to expose your skin to relatively cool temperatures. Colder 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 an additional boost in cellular activity.
How cool do you have to be? In addition to their studies with vests containing 57°F water, Drs. Kahn and Cypess have also 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 put subjects in an even milder setting of 66°F, and found that more than half of subjects under age thirty-eight showed signs of brown fat activation. (For the over-thirty-eight group the results were less impressive, with fewer than 10% showing any brown fat effect.) In another study conducted by a group of Canadian researchers, subjects wearing a suit containing tubes filled with 64°F water burned about 250 extra calories over three hours, most of which appeared to be the result of increased brown fat activity.
What to Do
These experiments indicate that lowering the thermostat of your residence to the mid-60s or below may be enough to stimulate at least some brown fat activity. You can also activate your brown fat by dressing more lightly in cool weather. For people willing to expose themselves to even cooler temperatures, a number of cooling vests are available (see box on page 144: Cooling Vests for Brown Fat Activation). In fact, our Joslin group is working on their own version right now. Research is also now underway to investigate whether exposing just one part of the body to cooler temperatures (by wearing a cooling band around your arm or leg, for example) might be enough to stimulate brown fat activity.
Activity Tip: You can boost the amount of calories you burn during exercise by stimulating your brown fat stores during your workout. Make a point of exercising in relatively cool temperatures—62°F to 64°F or lower. Making sure your skin is exposed while you’re exercising may be even more beneficial because the evaporation of sweat as you exercise adds to the cooling effect. What you don’t want to do is try to increase how much you perspire by turning up the heat when you’re exercising, because this hotter environment will actually shut down brown fat activity.
Foods that May Activate Your Brown Fat
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-carbohydrate diet before such scans, on the grounds that this reduces brown fat activation. This suggests, of course, that eating a low-fat, high-carbohydrate diet (like the RAD eating plan recommended in Strategy Chapter 1) will boost brown fat activity.
In addition, animal studies have found that the herb bitter melon appears to increase activity of brown fat and that 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 containing 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. Ursolic acid is also available in supplement form.
Although the benefits of exercise for your cardiovascular health, glucose control, and weight management are well known, researchers are now discovering that working out may have a positive effect on brown fat activity as well: Studies have found that irisin, a newly identified hormone that is produced during exercise, actually works to convert white fat into a variation of brown fat known as beige fat (see
These findings show that both brown and beige fat can burn calories and, even more exciting, that the two types of fat are activated in different ways—with cool temperatures inducing brown fat to become active and exercise transforming white fat into beige fat. This suggests that there are actually multiple ways to increase your calorie-burning fats and reduce the amount of unhealthy, calorie-storing white fat in
George King, M.D., is a professor of medicine at Harvard Medical School.
From: Reverse Your Diabetes In 12 Weeks by George L King, M.D., Workman Publishing