Leptin is a hormone secreted by fat cells of our body. Leptin is in news because it signals the brain to eat less and store less fat in the fat cells thereby causing fat loss. Leptin was in news recently (in the 90’s) and still continues to be so due to its ability to regulate appetite, energy expenditure and fat loss.
A team led by Jeffrey Friedman, M.D., Ph.D., professor at The Rockefeller University came to the limelight due to a study documenting nearly 30 percent weight loss in genetically obese mice by giving daily injections of leptin for two weeks. During the period of “leptin therapy” the mice ate less and spent more energy.
In their later study, the same investigators found that the greater the BMI (Body Mass Index) and percent of fat, the higher the levels of leptin. In humans too, it was found that, generally, the more the amount of body fat of a person, the more the amount of leptin in his or her blood. But this correlation was not found to be true for all persons. For example, the blood leptin level of a person with BMI < 20 was similar to that of a person with BMI > 40.
87 lean as well as obese people were selected for this study, among which 59 were Americans of different ethnicities and 28 were Pima Indians, a population with high rates of obesity. Age range of the study population was from 20 to 65. There were 50 women and 37 men in this study.
The scientists think that reduced sensitivity to leptin (“Leptin Resistance”) in some people could explain why obese people resist fat loss in spite of the fact that more leptin is found in obese people.