Leptin is a hormone produced by the fat cells. It appears to play a role in making someone feel full (satiation). When weight loss researchers created rats who were not able to make leptin, the rats became voracious eaters and obese.
Children born with the human genetic disease called Prader Willi Syndrome can’t stop eating, becoming severely obese before they are teenagers. With Prader Willi Syndrome, weight loss researchers have discovered that the signaling mechanism for leptin is broken (there is a mutation in the receptor which receives the signal from the leptin). Those children never feel full, so they keep eating.
Weight loss researchers have discovered that children who were born premature and/or underweight frequently became overweight or obese adults. In a new study, weight loss researchers evaluated infants who were underweight, low body fat percent, and breast-fed. Those infants had double the normal leptin levels. This may help explain why they become obese in adulthood.
Low body adiposity and high leptinemia in breast-fed infants born small-for-gestational-age.