Beating the Urge to Eat (page 2 of 2)

Anti-Fat Pharmaceuticals

The findings show why so many people who lose weight will gain it back again. But they also offer hope. By zeroing in on the biochemical pathways that control hunger and satiety, scientists are already coming up with promising new ways to fight obesity. Researchers at Rockefeller University are currently testing whether giving leptin to people who have lost significant amounts of weight will help them keep the weight off. Other biochemicals may also yield fat-busting drugs. Friedman recently announced the discovery of an enzyme called SCD-1 -- controlled by leptin -- which the body needs to build fat cells. When researchers at the University of Wisconsin deleted the gene that makes SCD-1 from mice, the animals were able to feast on high-fat meals without gaining weight.

The Fat Virus
While some researchers search for the roots of obesity in our genes, others investigate infections. Scientists have known for two decades that, surprisingly, certain viruses can cause birds or mammals to become fat. Now Nikhil V. Dhurandhar, a nutritional biochemist at Wayne State University in Detroit, thinks he's tracked down a bug that can cause obesity in people.

The alleged culprit is human adenovirus-36, or AD-36. In a study published in 2002, Dhurandhar showed that AD-36 injected into monkeys causes dramatic weight gain. In some animals the virus caused body fat to triple. It's unethical to inoculate people with the virus, of course. But in an analysis of 1,000 people, Dhurandhar and his colleagues found that those with AD-36 antibodies -- a sign that they've been infected -- are significantly more likely to be overweight.

How could a virus make you fat? When fat cells are exposed to AD-36, Dhurandhar has found, they begin to multiply. "I'm not saying all obesity is caused by a virus. Genes, metabolism, habits all play a role," he acknowledges. "But at least one other possibility appears to be infection."

As yet, no one knows how widespread AD-36 may be, or how big a role it might play in the current obesity epidemic. If Dhurandhar's suspicions prove correct, the next step would be developing a vaccine.

The Fidget Gene
Assuming you're not carrying an exotic virus, your weight will be determined -- in part -- by how much you eat. Equally important is how much you move, and here, too, researchers are learning that genes play a powerful role. Scientist Eric Ravussin has found that basal metabolic rate -- the number of calories we burn just to keep all basic systems running -- varies among individuals by as much as 500 calories a day. A low or high metabolism runs in families, proving that it is genetically controlled.

Ravussin's experiments turned up another trait that determines how fast we burn calories: fidgeting. "Some people jiggle their legs, tap their fingers, and otherwise fidget more than others," says Ravussin. The tendency runs in families. In a recent study at the Mayo Clinic's Endocrine Research Unit in Minnesota, physician James Levine fed 16 people an extra 1,000 calories a day. After two months, the natural fidgeters in the group weighed the same; those who barely moved had gained 12 pounds.

explains. Researchers have identified a protein that, when injected into animals, turns on fidgeting. Says Levine found that the fidgeters were more sensitive to calories. "They unconsciously increase their activity level after they eat too much," LevineLevine: "Give rats a shot of this protein and they start zipping around the cage. When they stop getting injections, they get slow and lazy again." Scientists have already tested several metabolism-boosting substances in humans, including dinitrophenol and thyroid hormone. Unfortunately, both have potentially dangerous side effects, so they can't be used as drugs. Still, the researchers are confident they're nearing a breakthrough.

Changing the World
"We can't ignore genes," says Steven Heymsfield, who studies metabolism and obesity at St. Luke's-Roosevelt Hospital Center in New York. "But we can't ignore environment either."

And environment is something we can change. "We choose the world we live in, after all, both individually and collectively," says Charles Billington, associate director of the Obesity Research Center at the University of Minnesota. "It's up to us to decide what we eat and don't eat. It's up to us to decide whether to watch an hour of television or go for a walk. We're shaped by our genes. But we're not their victims."

Now that some members of the food industry have begun to reduce portion sizes and raise nutritional awareness among customers, future generations may be able to reverse the disturbing weight trends we're facing. But as we grapple with change, the latest genetic findings offer hope to the overweight and obese. "Patients used to blame being overweight on glands and hormones, and we doctors would say, 'It's not hormones, it's calories,' " says Banks. "Now we know hormones are involved."

And the hunger cues those hormones stimulate may be so strong in many people that even the steeliest willpower isn't enough to resist them. Friedman, whose discovery of leptin jump-started research into anti-fat pharmaceuticals, says it's unrealistic and unfair to expect severely obese people to use sheer willpower to fight the powerful genetic forces that drive them to put on pounds. "People can diet and lose 10 or 15 pounds. But real obesity isn't a willpower problem. It's a medical problem."

From Reader's Digest - July 2004

 

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