Leptin & Appetite

Leptin has a theoretical benefit for treating obesity because it helps control appetite. However, as of 2011, researchers have not figured out how to harness this appetite-regulating hormone to promote weight loss and have not pinpointed all of the ways it affects the body. Leptin triggers signals in your hypothalamus, the part of the brain that controls hunger.

Identification

Leptin is a satiety hormone. It's produced primarily by your fat cells, though some is produced in your stomach as well. This hormone suppresses your appetite between meals. It works on a feedback system to maintain your body composition. When you gain body fat, leptin production is stimulated, which should lead to reduced food consumption. When you lose body fat, leptin is suppressed and your appetite increases.

Significance

A blunted response to leptin may be a factor in cases of obesity. Since the amount of leptin produced increases with gains in body fat, this rise in leptin should help stem the amount of food you eat as you become more obese. However, some obese people appear to be resistant to leptin's effects, according to a 1998 review in the "British Society for Neuroendocrinology." This could be a genetic issue due to a mutation in the leptin gene, says lead review author David Sunter. People also may develop leptin resistance, similar to insulin resistance experienced in cases of diabetes, according to other theories, says "The Aquavore Diet" author William H. Dunn. If this is the case, scientists may be able to determine a way to reverse leptin resistance, the way diet and exercise can help with insulin resistance.

Research

Animal studies on using leptin to regulate weight appear promising, according to Sunter. Rodents receiving leptin injections into the bloodstream or brain experience weight loss due to reduced food intake. The higher the amount of leptin administered, the more dramatic the effect, according to Sunter. However, leptin is not the only hormone to stimulate appetite. The gastric hormone ghrelin, for example, also prompts you to eat. Also, scientists are still working to understand exactly how leptin works to control appetite. It may regulate appetite as well as energy expenditure partly by reducing serotonin release and synthesis from brain-stem neurons, according to a 2010 study published in "Journal of Experimental Medicine." Scientists are studying this hormone's other effects in your body as well, such as its effects on fertility, according to a 2002 study published in "Seminars in Reproductive Medicine."

Stress, Sleep and Leptin

Lack of sleep that is associated with activation of your stress system may affect your leptin levels by decreasing them, according to a 2010 study published in the "Journal of Sleep Research." This may increase your hunger and appetite, prompting you to seek "comfort" food. Lack of sleep unrelated to stress does not appear to have the same effect, the study notes. As with hunger, your hypothalamus also is responsible for regulating sleep and mood.