What is Leptin?
Leptin is a hormone – a chemical messenger that helps different body parts work together. Leptin is anorexigenic (= causing loss of appetite), and levels are markedly decreased in women with low body weight and high in obesity. Leptin secretion follows a circadian pattern, meaning that the concentration in blood will vary throughout a 24-hour time period (higher at night than during the day).
What does Leptin do?
Leptin is an appetite suppressant. When everything works the right way, it helps you maintain a healthy weight by balancing the amount of food you eat with how much fat you have. Leptin sends a signal to your brain that helps you feel full and less interested in food. You may hear it called a satiety hormone. (Satiety means hunger feels satisfied.) It also plays a role in how your body turns fat into energy.
In a normal feedback response, a low level of leptin triggers hunger and an increase in food consumption. As the level of leptin rises from an increase in fat cells, hunger diminishes and food consumption drops off.
→ When a person eats enough food, leptin is released into the bloodstream, where it travels to the brain, signalling that they are full and that they can burn calories at a normal rate.
Leptin is produced primarily by fat cells (adipocytes) and to a lesser degree by other tissues, including the placenta in pregnant women.
Leptin and obesity:
Because leptin is produced by fat, leptin levels tend to be higher in people who are obese than in people of normal weight. However, despite having higher levels of this appetite-reducing hormone, people who are obese aren't as sensitive to the effects of leptin and, as a result, tend not to feel full during and after a meal. Ongoing research is looking at why leptin messages aren't getting through to the brain in people who are obese.
Leptin levels will often decrease when an obese person loses weight and increase when a person becomes obese, but they do not otherwise respond to lifestyle changes.
In those with very rare inherited leptin deficiencies, replacement therapy has been successful in addressing obesity. However, there are insufficient data at this time to support its routine use for other leptin deficiencies.
Do Certain Foods Boost Leptin?
You don’t get usable leptin from food, and there’s no evidence that specific foods help boost the hormone. But a poor diet or extra pounds may make the hormone less effective (leptin resistance).
→ A healthy, balanced diet and regular exercise may help keep this problem at bay.
Reference Ranges for Leptin:
Adult Lean Subjects (18-71 years) with BMI range of 18-25:
Adult Subjects (19-60 years) with BMI range of 25-30:
Pediatric Reference Ranges for Leptin:
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Allison MB, Myers MG Jr. 20 years of leptin: connecting leptin signaling to biological function. J Endocrinol. 2014 Oct;223(1):T25-35. doi: 10.1530/JOE-14-0404. PMID: 25232147; PMCID: PMC4170570.
Rosenbaum M, Leibel RL. 20 years of leptin: role of leptin in energy homeostasis in humans. J Endocrinol. 2014 Oct;223(1):T83-96. doi: 10.1530/JOE-14-0358. Epub 2014 Jul 25. PMID: 25063755; PMCID: PMC4454393.
Schwartz MW, Woods SC, Porte D Jr, Seeley RJ, Baskin DG. Central nervous system control of food intake. Nature. 2000 Apr 6;404(6778):661-71. doi: 10.1038/35007534. PMID: 10766253.
Karen K. Miller and others, Decreased Leptin Levels in Normal Weight Women with Hypothalamic Amenorrhea: The Effects of Body Composition and Nutritional Intake, The Journal of Clinical Endocrinology & Metabolism, Volume 83, Issue 7, 1 July 1998, Pages 2309–2312, https://doi.org/10.1210/jcem.83.7.4975
Paz-Filho G, Mastronardi CA, Licinio J. Leptin treatment: facts and expectations. Metabolism. 2015 Jan;64(1):146-56. doi: 10.1016/j.metabol.2014.07.014. Epub 2014 Aug 3. PMID: 25156686
Pereira S, Cline DL, Glavas MM, Covey SD, Kieffer TJ. Tissue-Specific Effects of Leptin on Glucose and Lipid Metabolism. Endocr Rev. 2021 Jan 28;42(1):1-28. doi: 10.1210/endrev/bnaa027. PMID: 33150398; PMCID: PMC7846142
Insufficient leptin can cause persistent hunger as the body attempts to protect itself from perceived underfeeding (starvation). Very rare inherited leptin deficiencies can cause severe obesity through constant hunger and constant eating that starts in early childhood. Leptin replacement therapy has been shown to be successful in treating some of those affected.
In the obese, decreased leptin levels may indicate some degree of deficiency, while increased concentrations are thought to be associated with resistance to the effects of leptin. Most obese people will have increased levels, but about 10% may have some degree of leptin deficiency.
Very rarely, significantly decreased leptin levels may indicate an inherited leptin deficiency linked to severe obesity.
Obesity is most commonly associated with elevated leptin levels. This is thought to be due to a resistance to leptin that is similar to the insulin resistance often seen with obesity. People who are affected are resistant to the action of leptin - they continue to experience hunger even after consuming sufficient food. The body continues to produce more leptin in an attempt to compensate and in response to the perceived hunger. However, about 10% of those who are obese are estimated to have some degree of leptin deficiency.
There is significant interest in better understanding leptin’s ties to obesity. Obesity is a major health concern in the U.S. because it increases the risk of many conditions, such as high blood pressure (hypertension), dyslipidemias (high cholesterol and/or high triglycerides), type 2 diabetes, joint problems, sleep apnea, coronary heart disease, stroke, and some cancers. The rate of obesity has increased steadily over the last 20 years in all age ranges and, according to the Centers for Disease Control and Prevention, more than one-third of adults and 17% of children and teens in this country are currently classified as obese. Classification is based on body mass index or BMI.
A recent study found that in some people a leptin level might be more accurate than the traditional body mass index in gauging how much excess fat a person is carrying. In general, the higher the level of leptin in the bloodstream, the more fat tissue a person has. In the study, this was especially true with older women and in those with large muscles or dense bones where the results of the BMI score could be misleading.
Research is ongoing to evaluate leptin’s roles in the body and the links between leptin and obesity, and between leptin and successful weight loss. There is also continued interest in determining whether a leptin-based treatment might be useful for those who are obese and leptin-deficient.
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