Ghrelin is a hormone found primarily in the stomach, though it exists in other areas of the body as well. Over the past several years, ghrelin levels in the human body have garnered a great deal of attention, as a link was found between the hormone and control of hunger. While researching ghrelin levels, scientists found that the hormone increases feelings of hunger when it is increased in the body. In addition, high levels of ghrelin have been found to suppress the amount of fat used by the adipose tissue. This implies that those with high levels of ghrelin in their bodies will not only feel hungrier than those with low levels, but may burn fat more slowly as well.
Interestingly, a 2004 study found that obese individuals tend to have lower ghrelin levels than those who are thin. In thinner individuals, however, ghrelin levels appear to rise between midnight and dawn, when most people are asleep. Therefore, thinner individuals most probably sleep through this period of increased hunger. This had led researchers to believe that obese individuals may have a problem with their circulatory system.
On a related note, additional research has indicated that lack of sleep can also cause obesity. This appears to be related to an increase in appetite, which may be spurred on by increased ghrelin levels. In fact, lack of sleep appears to cause the body to produce more ghrelin. Not only does ghrelin stimulate the appetite, but it also it suppresses the creation of leption, which helps suppress the appetite.
Other relationships have also been found between weight and ghrelin levels. One study found that individuals who undergo gastric bypass surgery experience lowered ghrelin levels. Individuals suffering from anorexia nervosa, on the other hand, tend to have higher ghrelin levels.
Despite the research into ghrelin levels and the many interesting findings, researchers are still unsure of the exact relationship between ghrelin levels and obesity. Namely, it is still unclear whether high levels of ghrelin cause obesity or whether obesity causes ghrelin levels to increase.