The Slimming Hormone

We all know it takes motivation to keep focused on goals, such as to eat better and get more exercise. The good news is that a little bit of effort can boost motivation by setting big rewards in motion.

A study conducted at the University of Florida suggests that dieters who persevere long enough to lose a few pounds may get help from a hormone that's otherwise stifled by excess fat.

In the study, adult rats fattened on a high-calorie diet returned to their original weights when scientists delivered the "slimming hormone," called leptin, to the rodents' brains. According to Dr. Satya Kalra, a professor of neuroscience, leptin is produced by mammals, including you and me.

The findings suggest that some day, the hormone could eventually provide better weight-control methods. For now they indicate that unwanted pounds are best fought with persistence and prevention.

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"The take-home message is it's very important that we maintain a healthy lifestyle," says Kalra, "That includes a lot of energy expenditure through exercise and tight control on calorie intake."

Leptin, produced in our fat cells, helps regulate energy use by signaling the brain to reduce appetite and burn more calories. But there's a caloric Catch-22: Overweight animals produce excess leptin, so much that it impairs the very mechanism that should eliminate excess fat.

For reasons that are not clear yet, when leptin levels are increased in the blood, leptin is ineffective in performing its normal function. Scientists call this "leptin resistance." "It increases more quickly if the animal consumes a diet that's very rich in calories," says Kalra.

For several years, he and his colleagues have sought to get around leptin resistance in animals by delivering leptin-producing genes to the hypothalamus, an area of the brain that controls many basic body functions. It's where the body's feeding center is located. They focused on a tiny portion of the hypothalamus called the paraventricular nucleus. That's where assorted brain chemicals act to stimulate or inhibit appetite and it's the home of neural circuits that increase energy expenditure.

In the study, a group of animals were made obese on a diet made up of 45 percent fat. After 80 days, they weighed 20 percent more than a group of animals fed a normal diet of 11 percent fat.

Then the obese animals were given a shot of leptin-producing gene into the paraventricular nucleus. Fifty-six days later, those that received the leptin gene were now only 3 percent heavier than they were when the experiment began.

Kalra thinks that in the fat rats there's some kind of insufficiency of leptin in the brain areas where leptin normally works—just as there is in 95 percent of dieters. There's no magic pill for easy weight loss, but exercise and good nutrition are as reliable as ever, Kalra says. "It's important to emphasize both."

And you are definitely not alone. Currently, almost 59 million Americans are considered obese, with a body mass index of 30 or more, based on excess fat in relation to lean body mass.

So start the ball rolling—literally—and your leptin will begin leaping to your defense.

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