By Dr. Mercola
When it comes to body fat, most Americans are concerned with losing as much of it as possible. But this is referring to white fat, which is the type that typically accumulates on your belly and thighs.
Another type of fat is called brown fat, and emerging research suggests that many people may be better off increasing this beneficial type of fat. In fact, a new study revealed that one reason you may have trouble staying slim as you get older is because your levels of brown fat generally decrease with age.
Are Falling Brown Fat Levels Responsible for Middle-Age Spread?
Most people are familiar with age-related weight gain or obesity. As you get older, you have to watch your diet more closely and stay more active just to maintain your weight, let alone lose any. Meanwhile, when you were in your 20s, you could eat whatever you wanted without gaining a pound.
One reason for your body's propensity for weight gain as it ages may have to do with decreasing levels of brown fat, which occurs naturally as you get older. Brown fat is a heat-generating type of fat that burns energy instead of storing it, and this may have important implications when it comes to weight loss.
It is colored brown because it is loaded with mitochondria that convert the fat directly to energy to produce heat. Researchers initially thought its primary function was to help produce heat in the absence of shivering.
Human newborns have a generous supply of brown fat to keep warm, but by adulthood they lose most of their stores of it. Until just a few years ago, it was thought that adults had no brown fat at all, since you can adequately shiver as a way to keep warm (babies, on the other hand, cannot).
Newer research revealed that not only do adults have some brown fat, but it appears to have physiological roles beyond heat generation. These roles are just now beginning to be explored…
In one recent study, mice that had a gene known as platelet-activating factor receptors (PAFR) knocked out became far more obese with age than the normal control mice. The PAFR gene is responsible for inflammation and fat transfer, and it's thought that deactivating it impaired the function of brown fat, causing the mice to become quickly obese.1
The researchers are looking into ways to pharmacologically target the pathway that might deactivate the PAFR gene in humans, thus contributing to obesity. However, there are likely a number of natural ways to boost your brown fat stores.
As for what this has to do with your age… it's known that as you get older, the thermogenic activity of brown fat is reduced, similar to what happened with the mice in the study. This "failing" of brown fat is likely a key reason why there's a tendency to gain weight with age. The FASEB Journal's editor-in-chief noted:2
"A common complaint is that older people have to work twice as hard with their diets and exercise to get half of the results of younger people. Now we have a much better idea why this is the case: Our brown fat stops working as we age."
Characteristics of Those with Higher Levels of Brown Fat
Brown fat has been located in the neck area, around blood vessels (helping to warm your blood), and "marbled" in with white fat in visceral fat tissue. It's now thought that virtually everyone has small amounts of brown fat in their body, although certain groups of people tend to have more brown fat than others. Interestingly, it appears that the more brown fat, or the more activated brown fat, the better, as there are direct correlations between the activation of brown fat and metabolic measures of good health. For example:
- Slender people have more brown fat than obese people do
- Younger people have more brown fat than elderly people
- People with normal blood sugar levels have more brown fat than those with high blood sugar
Women also tend to have more brown fat than men, and people taking beta blocker drugs to treat high blood pressure have less active brown fat. The latter is likely because catecholamines, which are hormones released as part of your body's natural "fight or flight" response, are known to activate brown fat, but beta-blockers block catecholamines, thereby suppressing the activation of beneficial brown fat.3
A 'Master Switch' for Brown Fat Production?
Over the past five years, Bruce Spiegelman, PhD, with Harvard University's Dana-Farber Cancer Institute, and his research team has published at least five studies4 on the topic of brown fat, and in one, they identified a sort of master switch that promotes the production of brown fat, and may also be involved in the conversion of white fat to brown fat. In 2008, they showed that the molecular switch, known as PRDM16, regulates whether immature cells will turn into brown fat or into muscle cells. In an interview with WebMD, Spiegelman said:5
"We showed that brown fat and white fat have completely different origins. Brown fat is derived from muscle. That was a huge surprise."
Another set of researchers from Harvard's Joslin Diabetes Center found another trigger for brown fat—a protein called BMP-7, which also promotes bone growth.6 The researchers discovered that this protein acts as a growth factor for brown fat. Mice treated with BMP-7 protein grew up to have more brown fat than untreated mice, and the treated mice also used up more energy. Needless to say, researchers are excited about the potential for a medical intervention that can help people develop more brown fat. But I would be cautious of any solution in a pill form. Instead, I'd suggest trying out some of the non-invasive methods that have been found to promote brown fat production and its activation.
Cold Temperatures May Activate Your Brown Fat
It appears that spending time in cold temperatures may be a valid, albeit uncomfortable, way to activate your brown fat. The finding is so strong that some researchers on the subject joked they would be opening a "frosty spa."7 In one study, scientists found that they were able to activate brown fat in adult men by exposing them to cold temperatures.8 The men burned more calories when cooled and lost white fat, the kind that causes obesity. According to the study's authors:
"Does human brown fat actually combust fat to release heat? ... Ouellet et al. demonstrate that metabolism in brown fat really is increased when adult humans are exposed to cold. This boosts the possibility that calorie combustion in brown fat may be of significance for our metabolism and, correspondingly, that the absence of brown fat may increase our proneness to obesity …"
Swedish research published in 2009 also found that cold temperatures increased the activity in the subjects' brown fat regions.9 In fact, cold-induced glucose uptake was increased by a factor of 15! Based on animal models, researchers estimated that just 50 grams of brown fat (which is less than what most study volunteers have been found to have) could burn about 20 percent of your daily caloric intake—and more if "encouraged." Tim Ferriss, author of The Four-Hour Work Week, gave the following suggestions for putting this into practice (they range from easy to hard core):
- Place an ice pack on your upper back and upper chest for 30 minutes per day (you can do this while relaxing in front of the TV for example)
- Drinking about 500 ml of ice water each morning
- Cold showers
- Immersing yourself in ice water up to your waist for 10 minutes, three times per week. (Simply fill your tub with cold water and ice cubes)
Exercise May Turn 'Bad' White Fat Into 'Good' Brown Fat
In one mouse study, the animals converted white fat into brown fat simply by exercising. The study, published in the journal Disease Models and Mechanisms10 in May 2012 found that, during exercise, the animals' muscles released an enzyme called irisin, which triggered the conversion of white fat cells to brown.
It still wasn't for certain whether this would hold true in humans… until preliminary studies presented at the 2013 annual meeting of the American Diabetes Association showed that both mice and men experienced beneficial "browning" of fat following exercise. Among men, the benefits were found after 12 weeks of training on an exercise bike. One of the researchers, a postdoctoral fellow at Joslin Diabetes Center, said:11
"Our results showed that exercise doesn't just have beneficial effects on muscle, it also affects fat… It's clear that when fat gets trained, it becomes browner and more metabolically active. We think there are factors being released into the bloodstream from the healthier fat that are working on other tissues."
Getting a Good Night's Sleep, with Proper Melatonin Production, May Also Be Important
Consuming melatonin stimulates the appearance of "beige" fat, which, similar to brown fat, also helps your body to burn calories rather than store them. This, the researchers of one study believe, may explain why melatonin helps control body weight, along with its metabolic benefits.12 Science Daily reported:13
"The study… showed that chronic administration of melatonin sensitizes the thermogenic effect of exposure to cold, heightens the thermogenic effect of exercise and, therefore, constitutes excellent therapy against obesity. The fact is that one of the key differences between 'beige fat,' which appears when administering melatonin, and 'white fat,' is that 'beige fat' cell mitochondria express levels of UCP1 protein, responsible for burning calories and generating heat."
Though this wasn't discussed in the study, it's also well proven that lack of sleep is linked to obesity, while if you're not getting enough sleep, there's a good chance your melatonin production is not up to par either. The disturbance to your melatonin levels caused by lack of sleep (and exposure to light during the night) may be one more reason why it leads to weight gain, and this could have far-reaching impacts on your health.
Another Powerful Trick for Fighting Age-Related Weight Gain
We've covered exercise, proper sleep, and, potentially, cold water immersion therapy as methods for activating your brown fat for better weight management. Another powerful tool that can help you to fit back into the jeans you wore in high school? Intermittent fasting, otherwise known as scheduled eating.
Based on my own phenomenal experience with scheduled eating, I believe it's one of the most powerful ways to shift your body into fat burning mode and improve a wide variety of biomarkers for disease. The effects can be further magnified by exercising while in a fasted state. For more information on that, please see my previous article "High-Intensity Interval Training and Intermittent Fasting - A Winning Combo."
To get started, consider skipping breakfast and avoid eating at least three hours before you go to sleep. This should effectively restrict your eating to an 8-hour window or less each day. When you do eat, make sure to minimize carbs like pasta, bread, and potatoes. Instead, exchange them for healthful fats like butter, eggs, avocado, coconut oil, olive oil, and nuts—essentially the very fats the media and experts tell you to avoid.
You may also want to restrict your protein a bit if you're typically a big meat eater. I strongly suggest eating only high-quality pastured protein, and limiting it to about one gram of protein per kilogram of lean body mass (about one-half gram of protein per pound of lean body weight) may be appropriate for most people. (Note: if your body fat mass is 20 percent, your lean mass is 80 percent of your total body weight.)
These kinds of food choices, in combination with intermittent fasting, will help shift you from carb-burning to fat-burning mode, so you can stay fit and trim regardless of your age.