Genetic Factors Continued
A number of genes are responsible for regulating body weight.
More than a decade ago, researchers at Rockefeller University discovered that mutations in a gene—called the obesity (ob) gene— prevented a strain of mice from producing leptin.
Leptin is a hormone normally manufactured by fat cells, and released into the blood to inform the brain about the body’s level of fat stores.
When this communication system works properly, the brain responds to leptin by reducing appetite and speeding up metabolism to maintain a normal level of body fat.
Because the mice with the mutated ob gene did not produce leptin, their brains continually sent messages to the rest of the body to eat and store fat, and the mice became obese.
However, when leptin was injected into the obese mice, they quickly lost weight through a combination of decreased food intake and increased activity.
Since this discovery, however, researchers have found that administering leptin to obese people rarely reduces weight, because their blood leptin levels are already high and/or their bodies are resistant to the effects of leptin.
Still, unraveling the link between leptin (and other substances released by fat cells) and weight control may lead to the development of more effective drugs for weight loss.
