Decoding white and brown fat cells

Hyderabad: Women tend to put on weight around the abdomen and hips. This is because they have lower levels of brown fat or healthy fat, due to presence of follicle stimulating hormone (FSH), which is responsible for menses and ovulation.

In a study published in The New England Journal of Medicine and Cell Metabolism, scientists working with mice models found out how the white fat deposits in the abdomen and hip regions build up. But what converts brown fat into white fat is still not understood.

The study points to FSH whose levels rise at menopause and could be responsible for the characteristic redistribution of weight around the abdomen in middle age. The spurt in this hormone also causes loss of bone.

Dr Venugopal Pareek, senior gastroenterologist and obesity expert, said that FSH increases in blood during pre-ovulation and mid-cycle. “But it is also found to reduce during the pre-menopause stage in women. The levels of oestrogen drop significantly during menopause and this affects the bone strengthening capacity. There is significant loss of bone strength and that is one of the reasons to supplement oestrogen in post menopausal females.”

Experiments with mice have shown that blocking the hormone (FSH) increases the calories burned, reduces abdominal fat, slows bone loss and also encourages physical activity.

In mice, the brown fat got converted into white. But adults have very limited storage of brown fat. Dr Abhishek Katawar, senior bariatric surgeon, said that “brown fat is in abundance in new born children where it functions to protect them from cold. Recent investigations, however, have shown that adults also have metabolically active brown fat and it plays an important role. It is found in the front and back of the neck and upper back.”

It has the ability to burn calories and scientists are looking at ways of using it as it can help to fight obesity." There is no precise mechanism to understand how brown fat, which is predominant during childhood, gets converted to white fat. Scientific literature shows that the brown fat decreases with age; it is 50 per cent at the age of 20 to 29 years but less than 10 per cent after 40 years of age.