TWO TYPES OF BODY FAT
The human body possesses two distinct types of body fat, referred to as “brown” and “white.” Both forms of body fat are active, living parts of us, heavily influencing our metabolism. Most of this is in the form of white fat, which totals from about 5 percent of total weight in very lean male athletes to more than 50 percent of total body weight in obese individuals. Brown fat makes up only about 1 percent of the total body fat in healthy adults, although it’s much more abundant in healthy babies.
Brown fat, also called brown adipose tissue or BAT, helps us burn white fat; this is important for endurance. Without adequate brown fat activity, we can gain body fat; it’s most noticeable in cold weather when we can become sluggish like a hibernating animal. There are a number of ways to increase brown fat activity.
Certain foods can stimulate brown fat and increase overall fat burning. Eating several times a day, five to six smaller, healthy meals instead of one, two, or three larger ones, for example, can trigger a process called thermogenesis—an important post-meal metabolic stimulation for fat burning. However, if our caloric intake is too low, brown fat can slow the burning of white fat. This can happen on a low-calorie diet and when we skip meals.
Brown fat is also stimulated by certain dietary fats. The best ones are omega-3 fat from fish oil and extra virgin olive oil. While supplements of fish oil may be the only way to obtain adequate amounts of EPA, some supplements can be harmful; a popular supplement, CLA (conjugated linoleic acid), can actually reduce brown fat activity.
Capsaicin, the substance responsible for the pungent flavor of chili peppers, can stimulate brown fat. Use this in cooking and even on salads.
Other foods that increase brown fat activity include those with caffeine, but only if it’s tolerated. Tea, coffee, and chocolate contain small to high amounts of caffeine. However, if under stress, the adrenal glands become overworked, which can promote fat storage and reduce fat burning; caffeine may worsen adrenal stress in many athletes. Also, avoid coffee, tea, and chocolate products if they contain sugar, which can reduce fat burning.
Brown fat is greatly controlled by skin temperature. If we get too hot during training, brown-fat activity can lead to less burning of white fat. Dress light for training, or remove clothing as you warm up. Even sitting in a hot tub, sauna, or steam room regularly after an aerobic workout may offset some of the fat-burning benefits. Hot tubs and saunas do come with health benefits, but to avoid the reductions in fat burning take a minute or two to cool the body in a cold shower or tub afterward. In contrast, brown fat is stimulated by cold. Cooling the body’s brown-fat areas can help stimulate fat burning.
Brown fat is found around the shoulders and underarms, between the ribs, and at the nape of the neck. These are important areas to keep cool and from overheating after training. (Low body temperature is associated with reduced fat burning; this is often related to low thyroid function.)