Due to the hormone ghrelin which reduces appetite after eating not going down. >Recently, researchers discovered a so-called "hunger hormone" that rises just before eating and falls after a meal. Now, UK researchers have discovered that while this fluctuating pattern may occur in lean people, the hormone behaves quite differently in those who are obese.
Co-author Dr. Steve R. Bloom of the Imperial College at Hammersmith Campus in London, UK, and his colleagues found that obese people have lower-than-average levels of the hunger hormone ghrelin in their bodies when hungry, and these levels don’t change after obese people eat.
As such, obese people with unchangeable levels of ghrelin may not realize they are no longer hungry after eating.
"If, although low, (ghrelin) failed to go down properly after eating, you might still feel somewhat hungry inappropriately and eat more than you should," Dr. Bloom explained.
Ghrelin, a hormone produced by the stomach, is named for the Hindi word for growth. Past studies have shown it can make people so ravenous they eat nearly one-third more food than usual.
During the study, Bloom and his team measured the levels of ghrelin and the hormone leptin in 13 lean and 10 obese people, both when they were hungry and immediately after they ate.
Leptin is often called the "obesity hormone," because previous research has shown it may notify the brain to reduce appetite after eating, when fat cells are "full." The relationship between the two hormones is currently being investigated, but Bloom said that leptin may inhibit the body’s production of ghrelin.
The investigators found that, when hungry, lean people had more than twice the concentration of ghrelin in their blood of those who were obese. After eating, ghrelin concentrations did not change in the obese, but dropped 40% in lean people before inching back up to normal levels.
The concentration of blood leptin also decreased after eating in lean people, but showed no decline in those who were obese, according to the report in the June issue of the Journal of Clinical Endocrinology & Metabolism.
Bloom explained that researchers have not investigated whether low ghrelin levels induce obesity, or if obesity decreases the overall amount of ghrelin in the body. "This hasn’t been directly tested but it is assumed that the low ghrelin is a consequence of obesity," he said.
However ghrelin is involved in the development of obesity, Bloom suggested that manipulating the level of the hormone in the body may one day help to correct the problem.
"If a drug to block ghrelin could be identified–not difficult with modern mass chemical library screening–it would lessen hunger and tend to reduce food intake," he said.
"A 1% reduction in food intake for a year would have a major impact on obesity," Bloom added. SOURCE: The Journal of Clinical Endocrinology & Metabolism 2002;87:2984-2987