Leptin, Ghrelin, Cortisol and Weight
We take a look at leptin, ghrelin and cortisol, three of the most talked about hormones related to weight and weight-related behaviors.
Leptin is a hormone produced in the fat cells. It plays a role in regulating body weight by signaling to the brain to reduce appetite and burn more calories. Some studies have shown that losing weight causes a marked decrease in leptin levels, which may in turn increase appetite.1 More extensive research is needed, however, to confirm these findings.
Surprisingly, obesity is linked to unusually high concentrations of leptin. Some research suggests that these high, sustained concentrations make the receptor for leptin inactive and impair the very mechanism that should eliminate excess fat. 2 In other words, although plenty of leptin is produced, it is unable to function properly. It has been theorized that medications that target leptin receptors may be helpful for weight loss, however a great deal more research is needed and must be replicated in human trials before any firm conclusions can be drawn.
Ghrelin is a hormone released by the stomach that increases hunger,slows metabolism and decreases the body's ability to burn fat. During weight loss, some studies have found that individuals who lose weight and try to keep it off make more ghrelin than they did before losing weight, as if their bodies are fighting to regain the lost fat. The effects on ghrelin levels of a type of bariatric surgery, where part of the stomach is removed are inconsistent.3
Similar to leptin, ghrelin appears to work differently with excess weight. In a study that analyzed ghrelin concentrations, the researchers hypothesized that obese individuals would overproduce ghrelin. Unexpectedly, they were found to have less ghrelin in their blood than subjects at a normal weight. 4 An explanation for these findings is that excess weight may increase sensitivity to ghrelin. For example, there may be more receptors for the hormone, so not as much is needed to stimulate hunger.
Again, more research is needed before firm conclusions can be drawn about the effects of ghrelin.
Cortisol is a steroid hormone produced by the adrenal gland that increases as part of the body's response to stress. Most studies suggest that cortisol plays a very small role or is not related at all to body fat distribution and excess weight. Additionally, no research has found that taking cortisol-suppressing supplements are beneficial for weight loss.
This content is reviewed regularly. Last updated December 17, 2011.
While there is some research to suggest a connection between leptin, ghrelin, cortisol and weight, it is important to understand that the human body has a complex system of hormones that interact in a myriad of different ways. Therefore, it is not likely a simple one-to-one relationship between these hormones and weight, but rather part of a chain of physiological processes. Furthermore, there is not enough substantial evidence at this time to draw any firm conclusions.
1 Wang MY, Orci L, Ravazzola M, Unger RH. Fat storage in adipocytes requires inactivation of leptin's paracrine activity: implications for treatment of human obesity. Proc Natl Acad Sci U S A. 2005 Dec13;102(50):18011-6. Epub 2005 Dec 2.
2 Attie AD, Scherer PE. Adipocyte metabolism and obesity. J Lipid Res. 2009 Apr;50 Suppl:S395-9.
3 Tymitz K, Engel A, McDonough S, Hendy MP, Kerlakian G. Changes in ghrelin levels following bariatric surgery: review of the literature. Obes Surg. 2011 Jan;21(1):125-30.
4 Zhang N, Yuan C, Li Z, Li J, Li X, Li C, Li R, Wang SR. Meta-analysis of the relationship between obestatin and ghrelin levels and the ghrelin/obestatin ratio with respect to obesity. Am J Med Sci. 2011 Jan;341(1):48-55.