Health / Weight Loss

What Exactly Is Brown Fat?

Learn how to boost your metabolism by activating fat-burning brown adipose tissue.

The first thing most people gripe about during winter is the drop in temperature. But the cold and its effect on a particular type of fat may be the key to kick-starting your metabolism and heat production (thermogenesis). Recent research in the field of thermogenesis has focused on a particular type of body fat called brown adipose tissue (BAT), or brown fat, which plays a significant role in metabolism and thermogenesis.

What Is Brown Adipose Tissue?

We all know about white fat, the kind that stores excess food energy in pockets throughout the body. BAT is a different type of fat that burns fuel instead of storing it. It activates when the body is exposed to cold temperatures. Until recently, BAT was thought to only exist in infants, as they don’t have a well-regulated shiver response and need another way to generate heat.

It was thought that BAT stores were lost by adulthood. However, sensitive CT and PET scan imaging have enabled researchers to determine that people retain their stores into adulthood—predominantly in deposits between the scapular and neck area. BAT gets its name from the numerous mitochondria (little thermogenesis powerhouses) and the rich blood supply in the tissue, equipping it with all it needs to be a fuel-burning powerhouse.

How Does It Work?

When your body is exposed to cold, BAT is activated. It first uses stored glucose and then switches to white fat stores when the limited glucose supply runs out. The process of burning the high-energy fuel creates heat and your metabolic rate increases with sustained cold exposure. But you don’t need to stand outside in below-freezing temperatures for this to happen. In studies, for subjects who were placed in a 66-degree room (warm enough that they don’t start to shiver), scans showed that their BAT stores were activated. In comparison, subjects in an 80-degree room didn’t show any BAT activity.

Imaging has found that men tend to have lower amounts of BAT than women, and with age, BAT stores diminish. The mechanisms for loss of BAT with age aren’t clear but may be related to increases in body fat and reduced activity levels. Also, studies have shown that people with lower body mass indexes have higher stores of BAT. Conversely, obese individuals have smaller stores, an interesting finding that has spurred medical interest in how BAT may play a role in obesity and metabolism.

Related: Check your BMI using our Body Mass Index calculator

The latest focus in the study of BAT is on mechanisms that stimulate the recruitment of white fat into “beige” fat. Several studies have found that white fat cells can be recruited from functioning from a fat-storage site to a fat-burning, BAT-like tissue, called beige fat. A recent study discovered that when its subjects were exposed to a 63-degree room for two hours a day over six weeks, their number of calories burned during cold exposure increased over time. This finding led researchers to suggest that chronic exposure to cold temperatures may trigger the conversion of white fat to beige fat.

Tips for Boosting Your BAT Activity

The most effective way to increase your BAT activity is by exposing your body to colder temperatures. It’s not practical to live in freezing temperatures, but research has shown that exposing yourself to 66 degrees or lower for two hours a day is enough to activate BAT thermogenesis.

Acclimate yourself to colder temperatures by avoiding the impulse to crank up the heat. Initially, you’ll feel the chill. But, a short period of discomfort will pay off when your BAT stores activate and pump out heat. This will make you feel more comfortable at lower indoor temps.

Also avoid smoking, as studies have shown lower levels of BAT in smokers.

Adjust the thermostat.

Turn down your nighttime thermostat temperature. The benefit from this is twofold, as research shows that sleeping in a cooler room improves sleep quality. Sleeping in a warm room can disrupt your natural sleep cycle, increasing feelings of restlessness and insomnia. The Sleep Foundation recommends a nighttime bedroom temperature of around 65 degrees. But you may need to experiment to find the best number for your sleep.

Eat more complex carbs.

Eat your way to increased BAT activation by upping your intake of complex carbohydrates. A recent study found similar increases in BAT activity with both cold exposure and a carbohydrate-rich meal. The act of digestion increases thermogenesis. But there may also be an association with the type of food. For example, jalapeños and chili peppers can boost thermogenesis. So, if you like them, add them to your meals more often.

Also, eat more frequent, smaller meals. Every time you eat, your body revs up its metabolism to digest food. Plus, eating may play a role in BAT activity.

Spend time outdoors.

Find a winter sport you enjoy, and spend more time outdoors. Cross-country or downhill skiing, snowshoeing, and ice skating offer a twofold boost of metabolism with cold exposure and exercise.

Consistently exposing your body to colder temperatures is the key for acclimating to winter weather. If you continue to exercise outdoors as fall changes to winter, cooler weather will be easier to tolerate, and your body’s BAT stores will be at an optimal fat-burning level. Modify your workout so you can continue to exercise outdoors in every season.

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