THE GIST

- Compounds in chocolate may alter metabolism, reducing the fraction of calories that turn to fat.

- Go for dark chocolate with 60 to 70 percent cocoa.

- Try to stop after just a bite or two.

In a study that may seen like a dream come true, researchers have found that people who regularly eat chocolate tend to be thinner than people who don't eat chocolate at all.

Scientists still do not, unfortunately, endorse snacking on enormous piles of candy bars or massive bowls of chocolate ice cream. Nevertheless, the study adds to growing evidence that chocolate contains compounds that, in moderate doses, may alter metabolism, boost the energy efficiency of cells, and reduce the fraction of calories consumed that get deposited as fat.

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Eventually, the research may lead to obesity drugs that isolate chocolate's benefits in the pill form. In the meantime, the findings suggest that a square of chocolate after dinner most nights could help counter bulging waistlines.

"The presumption has always been that because chocolate is full of pesky calories and eaten as a sweet, that it would be associated with higher BMI," or body mass index, said Beatrice Golomb, an internal medicine doctor who studies oxidative stress and other topics at the University of California, San Diego.

"This is not a randomized trial and we shouldn't necessarily make recommendations from it, but for now, people can feel less guilty about moderate chocolate consumption," she added. "It does make me feel less guilty about telling my patients that chocolate is my favorite vegetable."

People have been tuned in to the health benefits of chocolate for at least 5,000 years, said Francisco Villarreal, a cardiology expert who is also a professor of medicine at UCSD but was not affiliated with the new study.

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The plant that produces chocolate beans, called Theobroma cacao, translates to "food of the gods." The Aztecs and Mayans used its beans both as money and as a treatment for a variety of diseases. And ancient warriors consumed cocoa to increase their strength.

In modern times, researchers have linked chocolate consumption to a bunch of good health outcomes, including lower risk of cardiovascular disease, lower blood pressure, lower levels of bad cholesterol along with higher levels of good cholesterol, and increased sensitivity to insulin, which helps maintain steady blood sugar levels.

Chocolate often gets a bad rap for being fatty and full of sugar, but in moderation, chocolate that's high in cocoa can have a positive effect on metabolism.CORBIS

With its relatively high fat and sugar content, though, chocolate has long been considered a fattening and sinful pleasure. To test that assumption, Golomb and colleagues surveyed more than 1,000 healthy adults, whose BMIs ranged from 17 to 50. Below 18 is underweight. Above 25 is overweight. And above 30 is obese.

Among the questions in the diet-focused survey, one asked, "How many times a week do you consume chocolate?" Those who answered with five or more had BMIs that were, on average, a full point lower than people who said they didn't eat any chocolate, the researchers report today in the journal Archives of Internal Medicine.

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Enthusiastic chocolate-eaters didn't exercise more than chocolate-avoiders, nor was their educational history or presumed socioeconomic status any different. And people who ate more chocolate actually ate more calories overall.

Along with other research, Golomb said, these findings suggest that something in chocolate is helping people process calories more efficiently.

The secret may be epicatechin, a naturally occurring compound in cocoa beans that has been linked to impressive health and exercise benefits in experimental settings. In one of Villareal's studies, for example, mice ran 50 percent farther after consuming a relatively small amount of epicatechin.

In another study, which included just five people with heart failure and diabetes, Villareal's team found that epicatechin restored severely damaged mitochondria, the cell's energy factories.

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One theory for how chocolate works its magic is that cocoa compounds strengthen and increase the number of mitochondria in cells, and that these effects are independent of any antioxidant activity that chocolate might have. In Golomb's view, cells that are stressed send messages telling the body to turn calories into fat. But chocolate reduces stress on cells, which can then use their extra mitochondria to burn calories instead.

Unfortunately for chocolate lovers everywhere, more is not necessarily better. In fact, Villareal said, according to his research -- both published and yet to be published -- the ideal dose of epicatechin comes in serving of five grams of chocolate, which is about the size of a single Hershey's Kiss. Consuming more than that can cancel out chocolate's potential benefits.

"When you eat a little bit too much, the effects just simply disappear," he said. "This is a very unique sweet point for peak effects."

Researchers recommend eating dark chocolate with between 60 and 70 percent cocoa. The brand doesn't matter, but pick kinds with cocoa butter instead of hydrogenated fats. And as hard as it may be to stop, just a bite or two is probably ideal.