Well, that's because obesity in humans does not simply depend on body `weight' but on the amount of body `fat'-specifically, adipose tissue.
According to The National Institute of Health,1 a healthy adult male's body should ideally have between 13 - 17 percent fat and a female should have 20 - 21 percent. Levels significantly above these amounts may indicate excess body fat. Therefore, you are considered obese, if you have a much higher amount of body fat than lean muscle mass.
Obesity, in today's world is an epidemic, with approximately 350 million obese (BMI> 30.0 Kg/M2) individuals worldwide. It is an established fact that consuming more calories than you burn, leads to being overweight and, eventually obesity, because the body stores unused calories as fat in the fat cells of the adipose tissues. It takes 3500 unused calories to make 1 pound of fat.
Now, imagine this.The stored fat cells are somehow `programmed' to burn off excess fat as heat? Wouldn't that be a wonderful story to hit the 8'o'clock news?
A recently completed research study at the Harvard Medical School has discovered how the body creates brown fat, the cells of which can burn white fat and turn it into body heat. Brown fat cells are known have a very different role from `regular' white fat cells. The white cells store fat whereas the brown cells burn it off as heat. Brown fat is commonly known as baby fat because it is found in newborns and infants and it helps them stay warm. Experts, till now believed that the brown fat disappeared during growth and therefore was not found in adults.
Dr. Spiegelman, the head researcher of this study has demonstrated how a pair of proteins, when injected into the body of a mouse, was able to switch on the brown fat cell's distinctive genes, thus enabling the conversion of both mouse and human skin cells into brown fat cells.
Dr. Spiegelman also has to his credit, another discovery (made in 2008) which confirmed that muscle cells are the natural precursors of brown fat cells. He has now found that a `zinc' finger protein, along with another protein produced in muscle cells, is the `activator' in the production of brown fat cells as well as for the conversion of skin cells into brown fat.
Dr. Spiegelman's team of researchers is hopeful that these results may be a future natural way to fight obesity. They cautiously state that such a therapy would never be recommended by itself but rather in conjunction with lifestyle changes and other interventions.
Having said that, the approach seems truly promising!
By. Padmashri Shanmugaraj, Dietitian, NutritionVista.comReference
1. http://www.nlm.nih.gov/medlineplus/ency/article/001943.htm