The LEPR gene provides instructions for making a protein called the leptin receptor, which is involved in the regulation of body weight. The leptin receptor protein is found on the surface of cells in many organs and tissues of the body, including a part of the brain, called the hypothalamus. The hypothalamus controls hunger and thirst as well as other functions such as sleep, moods, and body temperature. It also regulates the release of many hormones that have functions throughout the body.
The leptin receptor is turned on (activated) by a hormone called leptin that attaches (binds) to the receptor, fitting into it like a key into a lock. Normally, the body's fat cells release leptin in proportion to their size. As fat cells become larger, they produce more leptin. This rise in leptin indicates that fat stores are increasing. In the hypothalamus, the binding of leptin to its receptor triggers a series of chemical signals that affect hunger and help produce a feeling of fullness (satiety).
LEPR genetic variations that cause leptin receptor deficiency have been identified; this is associated with excessive hunger and massive weight gain. Some of the variations result in less receptor protein getting to the cell surface where leptin binding takes place. The receptors that get to the cell surface may bind to leptin, but their signaling function is impaired. The resulting shortage of leptin signaling disrupts normal feelings of hunger and satiety, leading to extreme weight gain.
Specifically, if you carry the C-allele in this gene, then you are predisposed to higher levels of leptin, glucose, and insulin that can result in chronic diseases such as obesity, diabetes mellitus, hypertension, and some cancers.
If you carry the G-allele in this gene, then you would be less likely to gain weight and would benefit from improvements in weight if you followed a Mediterranean diet.