Leptin and Obesity

Leptin is a hormone that your body produces while you're sleeping. It tells the brain when you've had enough to eat. Having less leptin, or a problem with the gene that produces it, is connected to weight gain and obesity. Too little leptin tells the brain, "I'm hungry," and promotes overeating. The opposite isn't true, however. Having a lot of leptin doesn't necessarily produce weight loss. With the discovery of leptin, the scientific community believed it was closer to finding an anti-obesity drug. Turns out, however, the way leptin works, especially in people who are obese, is complicated.

What is Leptin?

The word leptin comes from a Greek word meaning "thin." Also known as the "Ob gene" that is mapped to chromosome 7, leptin is a hormone that was largely unknown to the scientific community before 1994. Leptin's role is to achieve an energy balance by regulating your desire to eat and your calorie burn rate. As the amount of fat stored in your cells rises, leptin is secreted into the bloodstream and signals that make you eat more or less.

Leptin for Weight Control

Blood tests detecting leptin can determine the amount of calories stored in fat tissue in your body. A reduced leptin level is a precursor to obesity and a predictor of a failed diet. Scientists believe leptin also controls how your body responds to food deprivation. Studies are ongoing to determine how well it works to treat obesity. In a commentary published in the "Journal of Clinical Investigation" in 2008, Dr. Rexford S. Ahima of the University of Pennsylvania School of Medicine says it is possible "that preventing the decline in leptin level, via hormone replacement, could sustain the effects of dieting or drug treatment in obese patients."

Does it Work?

The promise leptin has for new weight-control programs has grown more complicated, according to articles in the "Los Angeles Times" and "Harvard Focus." In a review of the research, "Los Angeles Times" journalist Elena Conis reported that although the presence of leptin helps reduce weight, scientists still don't understand exactly how it works. Leptin was discovered in the mid-1990s when studies showed that mice given leptin ate less, but without it, they ate to the point of obesity. Later studies with people proved the same, but people who were obese already have higher levels of leptin than healthy-weight individuals, according to Harvard University researchers. The investigators concluded that there must be something wrong with the way leptin works in overweight people; they might have leptin-resistance, for example. Ongoing research is looking at how leptin signals the brain and affects mood, but an effective weight-loss drug is still a ways off.

Make Leptin Work

The body can override leptin's activity, and people who are obese can be resistant to it altogether. The good news is that leptin is secreted through stored fat cells. You can free up leptin to do its job by reducing body fat. By becoming more active and building muscle, your resulting weight loss allows your cells to become more sensitive and responsive to leptin.

Other Facts about Leptin

According to Drs. Mehmet Oz and Michael Roizen, authors of "You on a Diet," you have fewer leptin receptors in the brain as you age, which means you won't get as strong a signal that you're full. This is one reason weight gain becomes a problem as you get older. In addition, marijuana has its own receptors that overwhelm leptin, which is why people who use marijuana get the munchies. Drs. Roizen and Oz say that scientists are looking at how the drug turns off leptin so they can figure out how it turns on. The hoped-for result is a safe weight-loss drug that works through the body's hormones. Other studies show that having a high level of leptin, because of too much fat, increases your risk of certain types of cancer. Leptin also plays a role in high blood pressure, fertility, arthritis, migraines, blood sugar regulation and dementia.