Brown fat, its functions and how to increase it?

Basically, in humans and other mammals, there are two types of fat, namely, white fat or white adipose tissue and brown fat or brown adipose tissue. The former is bad fat whereas the latter is good one. White fat is much more plentiful than brown in the body. White fat stores energy and produces hormones which are then secreted in the bloodstream. Small fat cells produce a hormone called adiponectin which makes liver and muscles sensitive to hormone insulin, thus making us less susceptible to diabetes and heart diseases. When a person become fat, the production of adiponectin decreases or stops, thus making him or her more susceptible to diabetes and heart disease.

White fat stores fat whereas brown fat burns fat to produce heat. Brown fat also metabolizes glucose and fatty acids that is why it is important in diabetes and metabolic disorders.

Brown fat has recently acquired lot of buzz because of its usefulness in some particular ways. It is especially abundant in newborn and hibernating mammals. Its primary function is to generate body heat to prevent shivering. In contrast to white fat cells, which contain single lipid droplet, brown fat cells contain many smaller lipid droplets and higher number of mitochondria (storehouse of energy) which make it brown in color. Brown fat also has more blood capillaries than white fat since it needs more oxygen than most tissues.

Children have more brown fat than adults and it helps them keep warm. It has been found that brown fat is more active in people living in cold climates. This is to provide more warmth to the people living there. The amount of brown fat present varies from person to person. Certain populations have more brown fat than others. Scientists have found that brown fat burns more calories than white fat. Brown fat is hardly ever present in obese people. People with greater quantity of brown fat have lower body weight. Three ounces of brown fat can burn several hundred calories a day.

In a study the researchers have discovered that a type of bone morphogenetic protein called BMP-7 plays a key role in brown fat formation and its heat producing activity, which regulates body metabolism. In mice, there are two types of BAT (brown adipose tissue): constitutive BAT (cBAT), which develops before birth and recruitable BAT (rBAT), which is found in WAT (white adipose tissue) and skeletal muscles.

The researchers have discovered that when cBAT is deficient, cBAT cells send signals through systemic nervous system to increase production of rBAT within white fat. So there is a cross-link between two types of fat. The increase in rBAT maintains normal body temperature and protects against diet induced obesity in mice. Brown fat is essential for normal functioning of the body. When one type of brown fat is deficient, the body has a system for inducing development of other type of brown fat. It is yet to be found whether humans have also two types of BAT and how BMP affects human brown fat production.

Functions of brown fat-

• Brown fat produces heat whenever an organism is in need of extra heat, e.g., postnatally, during a febrile state or during hibernation.

• Brown fat has been called calorie incinerator. Brown fat actually causes the body to burn white fat when it is cold. The body becoming cold triggers this reaction.

• Brown fat reduces weight by burning regular white fat. When these brown cells own supply of fat runs out, they burn up white fat cells for fuel. Some researchers have found that a few ounces of brown fat burned about 250 calories in three hour time period.

• Brown fat releases a hormone called irisin on exercise, which apparently converts white fat into brown fat.

How to increase brown fat-

Exercise increases it- The scientists have noted that exercise produces a substance called irisin, which enters the blood stream and surfs to fat cells where it begins turning regular fat, especially deep, visceral fat around organs, into brown fat. Brown fat cells are metabolically active; they use oxygen and energy; they thus burn calories.

Diet- Taking a diet incorporating the following will help to increase brown fat in the body.

Eat six times a day to keep metabolism at an even keel

Get proteins from lean meats, poultry, seafood, eggs, soy, legume, nuts low fat dairy

Eat before and after workout

Eat variety of foods

Keep portions reasonable

Drink plenty of liquids

Eat high fiber carbs like fruits, vegetables, whole grains and legumes.

Cold increases it- Brown fat is activated by cold. In a study, the subjects were kept chilled but not to the point of shivering. It was found that their metabolic rates increased by 80%, all from the action of few brown cells. The brown fat also kept the subjects warm. On an average, the brown fat burned about 250 calories over three hours.

By transplantation- A new study shows that mice given brown fat transplants lose weight and avoid the metabolic changes that lead to type-2 diabetes even on high fat diet. The scientists hope that the transplantation of brown fat holds exciting potential for treatments of obesity and diabetes in people.