Are you addicted to fat?


Sure, we all are, say scientists who think they may have found a way to switch off your fat tooth.

CHOCOLATE ICE CREAM slowly melting under a glaze of hot fudge. Heavily marbled prime rib, tender at the center, crisply roasted at the edges. Or the good old American standby, a cheeseburger and fries. Name your weakness.

We all have one when it comes to high-fat fare, and most of us can't help caving in to our cravings-even when we're convinced that a low-fat diet will make us feel better, look better, and live longer.

In fact, if you believe some recent research on the chemistry of appetite, we're born with a craving for fat that can never be trained away. Look what happens when you serve Western fast foods in developing cultures brought up on rice and fish and vegetables, researchers say. The greasy new stuff always wins. Look, they say, at what's happening here at home.

Despite all the lip service being paid to healthful eating, Americans haven't really cut back much on fatty foods. We're eating less beef and butter, but we're filling the gap with other rich goodies. Take, for instance, super premium ice cream, which gets 60 percent of its calories from butterfat. Between 1992 and 1993, Americans' appetite for the high-fat dessert grew by 17 percent.

But this trend could well be more than just a national willpower outage. Neurobiologists say they've found a chemical pumped out by the brain that specifically triggers a craving for fat. And, sure enough, drug companies are now pouring dollars into a quest for a counteragent that would suppress our fat cravings without curbing our taste for protein or carbohydrates. By the end of the decade, some predict, you'll be able to resist that tempting doughnut by popping a pill.

The chemical incriminated in our fat craving is galanin, a neurotransmitter produced in the hypothalamus--a region of the brain known to play a key role in controlling appetite, metabolic rate, and fuel storage. This chemical control system is believed to work about the same in people as it does in lab rats.

"When galanin levels in rats' brains rise, the animals select high-fat foods. And an injection of galanin into the brain also stimulates animals to eat fat," says behavioral neurobiologist Sarah Leibowitz of Rockefeller University in New York City. Leibowitz has shown that galanin levels start out low in the morning but rise by lunchtime--stimulating the appetite for fat-and remain high until dinner.

Balancing the effects of galanin is enterostatin, a chemical produced by the pancreas. "When rats eat fat, enterostatin acts to inhibit fat appetite," explains David York, a physiologist at Louisiana State University in Baton Rouge. York has found that when offered fatty food some animals start out eating a lot of it but stop after a while. "Those rats produce high levels of enterostatin," York says. "Rats that produce little enterostatin continue to eat a lot of fat and become obese."

Leibowitz, in her studies, has also seen some rats with unusually big appetites for high-fat foods. These born fat-lovers show high galanin levels, she says, and they grow up plump.

It all makes sense. Human studies have shown that some of us really are born with a genetic tendency to put on pounds. These new findings may help explain how. Sadly, though, the news gets worse. The Rockefeller team found that in some rats, at least, eating fat seems to promote even more fat eating by prompting the brain to pump out more galanin. "The mechanisms that enhance the appetite for fat appear more potent than those that curb it," says Leibowitz. In other words, in nature's tug of war, fat usually wins.

Sociologists and anthropologists have their own explanations for why that might be. "It is very likely that humans' love of fat--which is universal--evolved as a survival tactic," says Claude Fischler, a sociologist with France's National Center for Scientific Research in Paris. Through most of human history, Fischler explains, people were hunters and gatherers who spent their time roaming around looking for food. "It makes sense that we should have evolved physiologic mechanisms that would make us eat fatty foods, which are easily stored as energy."

The main eat-me cue is taste, Fischler says. "In most foods, fat carries aroma and flavor through volatile fat-soluble molecules." Studies have found that fat enhances the response of taste receptors on the tongue and palate. Fat also gives food a pleasing texture, what food scientists call mouthfeel.

But until modern times it was a rare treat. "People lived primarily on low-fat plant foods," says Adam Drewnowski, director of the Human Nutrition Program at the University of Michigan School of Public Health in Ann Arbor. "Their main source of fat was meat, which they ate only infrequently."

Nowadays we're up to our chins in it. "As countries become more prosperous," Drewnowski says, "their consumption of animal products--the most fat-dense foods overall-always increases. This trend is continuing today in developing Asian countries, like Singapore, where animal-fat consumption has skyrocketed in tandem with an economic boom."

It all sounds like we're hopeless hostages to our animal urges; but not every researcher buys the idea. Biological anthropologist Stephen Bailey, of Tufts University in Boston, believes these theories are merely science's version of Rudyard Kipling's Just So Stories, fables about how the leopard got his spots and the giraffe a long neck. "It's a comforting thought," he says. "We don't have to take responsibility for eating too much fat. It's all in the genes."

In Bailey's view, however, culture plays a larger role. "People don't have an innate liking for fat any more than they have an inborn liking for Nike sneakers," he says. If the desire were innate, Bailey asks, why would it vary so much? "People in Asia," he says, "are definitely much less partial to fat than we are in the West."

As for the neurotransmitter theory, Bailey claims it's much too simple. "Though it's clear that compounds like galanin play an important role in controlling our appetites," he says, "it's also true that we're capable of generating a great variety of complex responses to the brain's signals. That is how we are different from rats."

In fact, some respected researchers have staked their careers on the promise that people can wean themselves off fatty foods. For years, internist Dean Ornish, director of the Preventive Medicine Research Institute in Sausalito, California, has been putting heart disease patients on a vegetarian diet in which a slim 10 percent of their calories come from fat. He swears he's had very few backsliders.

"It's easier to make radical changes in your diet than small ones," he says. "If you merely drop some high-fat items, you constantly feel deprived. But if you stick exclusively to vegetables, fruits, grains, and legumes, those are the foods you learn to enjoy. In time, eating high-fat foods becomes distinctly unpleasant."

That prescription may be easier to swallow for cardiac patients than for healthy ice cream lovers and French fry fans. They'll tell you the neurobiologists have it right: Fat's irresistible. Go ahead. Call them addicts. Call them fools.

Just don't call them late for dinner.

PHOTO (COLOR): Are you addicted to fat?



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