Word: leptin
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...least in laboratory mice. Genetically engineered mice that lacked the gene for making this hormone developed ravenous appetites and became grossly obese. When these same mice were injected with the missing hormone, they shrugged off a third of the weight they had gained. The researchers dubbed the new hormone leptin, after leptos, which is Greek for thin...
...Although leptin has since turned into something of a disappointment as an obesity treatment for humans--the vast majority of obese people turn out to have normal leptin levels--its discovery touched off a scientific gold rush that has yet to abate. Competing research teams in the U.S. and Europe have so far identified at least half a dozen other compounds that have surprising power to regulate appetite. Researchers at London's Imperial College of Medicine showed just last month that one of those hormones, dubbed PYY3-36, actually promotes a sense of fullness after a meal...
...pill, that the pill turns out to work for a wide range of people and that those who take it begin losing weight and shed, say, 5% to 8% of their body weight. At that point, some of the other hormones that affect long-term weight control, such as leptin and insulin, start dropping, and a short-acting hormone called ghrelin starts climbing, increasing your sense of hunger. "Now your body is competing with the effect of the drug," Schwartz says. "In the end, you may need two or three drugs to get the desired effect...
After all, we have been down this road before. When scientists reported in the mid-1990s that the absence of a hormone called leptin triggered the development of some very fat mice, it seemed that a cure for obesity was finally at hand. If these fat mice didn't make enough leptin, the reasoning went, then maybe fat people didn't make enough either. Would giving them leptin make them thin? The logic was so compelling that the pharmaceuticals firm Amgen reportedly paid tens of millions of dollars for development rights. It turned out, however, that most fat people...
...know about," says Michael Cowley, a neuroscientist at the Oregon National Primate Center in Beaverton and one of the co-authors of the Nature paper. Some of these biological traffic lights work in a very short time frame, affecting when you start and stop a meal. Some, like leptin, work over the longer term by helping the brain monitor how much fatty tissue the body has stored. PYY is a medium-term signal; it seems to suppress your appetite between meals, presumably so you can get some work done before you start eating again. What complicates things is that these...