The recently discovered "hunger hormone" called ghrelin is gaining a solid reputation for regulating how much food we eat and how much weight we gain.

Where is Ghrelin produced in the body and what does it do?

Ghrelin (pronounced GRELL-in) is produced mainly by the stomach, although it is also made in other organs, such as the intestines and the kidneys. Ghrelin has been dubbed the hunger hormone because in previous experiments people given the hormone became so ravenous, they ate markedly more than their usual food intake.

Does Ghrelin work differently in slim and obese people?

Another study found that in slim people, ghrelin levels peaked right before a meal but rapidly declined soon afterwards. In contrast, levels of the hunger hormone were lower than average in obese individuals, but they remained steady before and after a meal, suggesting obese people might still feel hungry after eating.

Are insulin levels and Ghrelin level connected in the body?

Other researchers report that insulin plays a role in regulating ghrelin levels. Ghrelin levels were monitered in 8 non-diabetic adults as they were given a 2-hour infusion of insulin. Shortly after the infusion began, levels of ghrelin began to drop. When the insulin infusion was stopped, levels of the hunger hormone began to rise and rapidly returned to normal.

Since insulin is already known to increase levels of leptin -- the "obesity hormone" that is thought to tell the brain to curb appetite after eating -- the findings suggest that insulin plays an important role in controlling what we eat.

Ghrelin represents one of the most promising breaking targets in the field of obesity. Although scientists only identified ghrelin in 1999, more than 200 papers on the substance have already been published. Ghrelin acts to stimulate food intake but blood levels are reduced in obese patients suggesting that this mediator represents a key regulator of food intake.

Journal of Clinical Endocrinology and Metabolism 2002;87:3997-4000, 4005-4008