The discovery of the leptin hormone by Dr. Jeffrey Friedman and his collegues at Rockefeller University offered a physiological cause for obesity and a promise of possible treatments. Friedman’s research, published in the December 1994 issue of Nature, studied obese mice found to have a leptin deficiency. These mice lacked the gene that codes leptin, and they weighed three-times as much as their siblings that did not have this genetic defect. When injected with a synthetic form of the hormone, the obese mice increased their activity and lost weight.
What is Leptin?
Leptin, named for the Greek word leptos, meaning thin, is a protein hormone that Friedman’s research found is produced by fat cells and sends signals the brain that regulate energy expenditures and food intake. During periods of fasting or famine, the body’s leptin levels decrease with the loss of fat; this both increases the appetite and signals the body to conserve energy in an effort to increase fat stores and leptin levels. The level of leptin required to satisfy appetite and signal the body that it has energy to expend varies among individuals and may be genetically determined. Several factors influence the amount of leptin released by fat tissue. Increased body mass, food and glucose intake all increase leptin levels. Exercise and increasing age lower these levels.
Low levels of leptin also affect fertility in women, protecting an undernourished body from the strain of pregnancy. This phenomenon, hypothalamic amenorrhea, is often associated with long-distance runners and ballet dancers.
Can Leptin Supplements Aid Weight Loss?
Leptin therapy has been effective as a weight loss treatment for individuals with leptin deficiency, but for the majority of obese patients, deficiency is not the problem. Most overweight people have adequate amounts of the hormone in their blood stream, but the leptin is not signaling the brain to suppress appetite or increase physical activity. This leptin resistance is similar to the insulin resistance suffered by type 2 diabetics; the hormone is plentiful, but it is not signaling the brain as it should. Researchers theorize that sustained periods of overeating causes the hypothalamus, the part of the brain that regulates hormones, to become less sensitive to leptin, requiring increased amounts to signal the body that it has taken in enough food. Another possible cause of leptin resistance is a defective system of delivery from the blood to the brain.
Products marketed as leptin supplements do not actually contain leptin. As a digestible protein, the hormone cannot be taken in supplement form. These supplements are generally designed to promote overall wellness, which supports the body’s system of regulating appetite and energy expenditures. Many of these supplements contain fiber to promote a sense of fullness and suppress the appetite. While no synthetically engineered leptin has yet been developed to overcome leptin resistance, a diet low in sugars may help improve the transport of leptin to the brain.