Leptin, a protein hormone produced by fat cells, normally controls appetite by signaling the brain that your body has taken in enough calories and can stop eating. Although overweight people have elevated leptin levels, their brains don't receive this signal. Leptin is manufactured in your body and isn't obtained from dietary sources. Since overweight people have higher than normal leptin levels already, they need to respond to the leptin they have, not add more, to lose weight. Do not take leptin supplements or injections without discussing their use with your medical practitioner.
Fat Cells
A gene called the obese, or ob, gene found in fat cells produces most of the leptin in your body, although the cells that line the stomach also make small amounts. As fat cells increase in size in overweight people, they produce more leptin. However, leptin doesn't appear to reach the hypothalamus to signal that the person has eaten enough and should stop eating. This condition, leptin resistance, not leptin deficiency, occurs in most overweight people, according to The Rockefeller University.
Injections
A small group of people don't make leptin. These people eat massive amounts because they never feel full. Giving them leptin in the form of injections helps them lose weight because then they respond to leptin signals, telling them that they're full, The Rockefeller University explains. Leptin injections may also help people who have lost weight keep the weight off, a study published in December 2005 in the "Journal of Clinical Investigation" indicates. According to the study, leptin levels dropped in 10 volunteers, three of whom were obese, when they lost 10 percent of their weight on a calorie-restricted diet. Giving them leptin injections twice a day to bring their leptin levels up to pre-weight loss levels increased their metabolic activity. Because metabolic activity slows after weight loss, many people regain weight after losing it. Leptin must be injected rather than taken orally, because leptin, a protein, breaks down in the stomach if taken orally and doesn't absorb well.
Supplements
Leptin supplements don't actually contain leptin, which can't be absorbed orally. What they contain is substances that claim to reduce leptin resistance so your brain responds better to signals that you're full and as such, you eat less.
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