NEW WAYS TO FIGHT FAT; SCIENTISTS SAY THE KEY IS FOOLING THE BRAIN.

Byline: Usha Lee McFarling Knight Ridder Newspapers

With nutrition labels slapped on food, magazines bursting with articles on how to eat right and a library of carbo-hating, calorie-busting books clogging best-seller lists, there's no shortage of dietary advice in this country.

Then why is everyone so fat?

It's a question that has public health experts so frustrated they're leaping beyond the traditional field of nutrition and searching for new remedies from experts in anthropology, psychology and neuroscience.

Among the radical answers; injecting healthy, low-fat foods such as brussels sprouts with enticing sweet and salty tastes; changing brain chemistry to steer people away from fat and chocolate, or even calming frenzied dieters whose obsessions can lead to dangerous eating patterns.

Weight gain was once seen as a simple energy balance problem: People ate too much and exercised too little. But now it seems more complicated - involving long-neglected social and psychological influences such as taste, anxiety and even memory.

Whatever the causes, more than half of American adults are overweight, nearly 20 percent are dangerously obese and those excess pounds contribute to 300,000 deaths each year, new figures reported last week show. The numbers have doubled in the last decade with no slimming in sight.

``You've got to figure out what motivates people so they can change their diet,'' Agriculture Secretary Dan Glickman said Wednesday at a daylong Agriculture Department symposium titled ``Why we choose the foods we eat.''

Some reasons are as close as the nearest fast-food counter.

People will generally eat as much as they are given, regardless of their physiological needs. So the giant servings famous in modern American life - from groaning buffets to super-sized fries - may explain why Americans are fatter and more prone to heart attacks than the French, who feast on small portions of fatty pates.

Cultural training

Choices about what and how much to eat are ``in the mind of the eater and the culture that trained that mind,'' said Paul Rozin, a professor of psychology at the University of Pennsylvania who researches cultural attitudes toward food.

Some diet-crazed Americans are so obsessive about fat and salt that they are far less likely to enjoy their food - but still eat too much for reasons that remain mysterious, Rozin noted.

Other research shows we may be hostage to brain chemicals that dictate our cravings, be they for meat, chocolate or pickles.

Evidence that the brain controls appetite first came from intriguing cases of patients who had suffered brain damage, said Dr. Charles Billington, a professor of medicine at the University of Minnesota.

One 20-year-old brain tumor patient ate continuously until she reached 300 pounds and her parents were forced to padlock the refrigerator and pantry.

In what has been termed ``gourmand syndrome,'' a 55-year- old man who had been a trim runner relatively uninterested in food suffered a stroke and became obsessed with fine dining.

Blocking appetite

Work by Billington and others shows that a variety of hormones and brain chemicals can increase or suppress appetite. Billington kept lab rats svelte by giving them a drug that blocked natural chemicals in the brain that trigger feelings of pleasure. That kept them from overindulging in extra-sweet rat chow.

Something similar might work on humans, he suggested.

But the chemistry may prove tricky, Billington said. He is less than enthusiastic about the prospects for a widely touted hormone called leptin that is being tested in humans for weight reduction.

``The overall effect doesn't appear to be very potent at this point,'' he said.

Brain chemistry also appears to contribute to our menu choices and how our bodies respond.

Sarah Liebowitz, a neuroscientist at Rockefeller University in New York, has shown that some brain chemicals cause rats to eat carbohydrates while others cause them to crave fat. In one of her experiments, a single high-fat meal caused a chemical called galanin to surge in a rat's brain. The extra galanin caused the animal to seek even more fat.

``We might actually have a vicious cycle here,'' she said.

Cravings for unhealthy food start when children are growing and need a lot of energy. Too much food and too little exercise is triggering dangerous weight gain in many children as young as 4.

New studies show the common parental strategy of restricting unhealthy food may backfire, causing children to obsess and eat even more when they're not being watched, said Leeann Birch, an expert on children's food preferences at The Pennsylvania State University.

Parents should continue to push healthy foods on children, she said, noting that their initial disdain often fades.

But the distasteful truth is that the healthiest foods - broccoli, onions, kale and tofu - are also the ones we are least likely to choose, because they are bitter. The simplest solution, suggested taste expert Adam Drewnowski of the University of Washington, might be to fool the tongue.

``We fortify our foods with folate, extra vitamins and so on,'' he said. ``It is now time to fortify them with extra taste.''