Word: ghrelin
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Dates: during 2000-2009
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...researchers are careful to emphasize only what they know for sure. Their study involved just 28 patients, and while the scientists came to three conclusions, lead author Dr. David Cummings of the University of Washington says, "I feel very solid about two of them." The first is that ghrelin levels in the bloodstream rise significantly before meals and drop afterward. This suggests that ghrelin is involved in triggering the desire to eat--and indeed, earlier studies performed since the hormone was discovered in 1999 have shown that a ghrelin injection just before a meal causes people to eat more than...
...second conclusion reached by Cummings and his colleagues is that ghrelin levels are higher on average in people who have lost weight from dieting. "It's well known that your body works against you when you try and lose weight," he says. If your weight falls below a certain "set point," which varies from one person to the next, your metabolism adjusts to bring you back. "What's new," explains Cummings, "is the possibility that a rise in ghrelin is one way it's done...
Cummings is less sure of the third conclusion, that bypass patients have only a quarter as much ghrelin as most people of normal weight. "It was based on only five people," he says, "and it's quite possible that had we studied a sixth, he would not show that." Still, the conclusion makes sense on its face. Ghrelin is produced mostly by cells in the stomach; if large parts of that organ are cut off from the rest of the digestive system, they may well stop churning out the hormone...
...while it's tempting to think that ghrelin is a magic bullet that could be used to keep us all at a perfect weight, doctors think that's highly unlikely. Similar hopes were raised a few years ago for leptin, a hormone that acts as an appetite suppressant. After years of trying, nobody has found a way to make it into a useful medication, largely because patients quickly develop a leptin tolerance...
What doctors suspect is that both leptin and ghrelin are part of a complex system of brain and body chemicals that have evolved over millions of years to govern weight and appetite. Says Dr. Rudy Leibel, an obesity expert and head of the molecular-genetics department at Columbia University: "It's just unlikely that any single component of this system will necessarily lead to a definitive therapeutic agent...