Wholesome Beauty: Actress Katie Holmes arrives for the In Style magazine and Warner Bros. party after the 61st Annual Golden Globe Awards on Sunday, January 25, 2004, in Beverly Hills, California.

A recent study published in the Archives of Internal Medicine reported that not all overweight people are necessarily at higher risk for cardiovascular diseases. This is being translated into headlines like, "Fit and Fat: Study Shows It's Possible."

Of course it's possible; doctors have known for many years that not everyone who is overweight is unhealthy. A person's overall fitness is more important to his or her health than numbers on the scale. For example, most professional football players would be considered overweight, yet they are healthier than average because of their level of fitness.

But the problem is that most Americans aren't like professional football players.

Most Americans — fat or thin — are not eating healthy diets, nor are they getting enough exercise. Physically active people are both fitter and thinner than people who do not exercise regularly. Researchers caution that the recent study does not show that being overweight is healthy; in fact, fat people had twice the heart risk as thin people.

Is big beautiful?

There's also of course a social element to obesity. As a nation we keep getting fatter, and for some people that's not a bad thing. Fat-acceptance groups and activists have tried for years to encourage the idea that fat is sexy. Countless books with titles like "Fat Chicks Rule!" and "Embracing Your Fat Ass" promote the message that big is beautiful. While their empowerment message is mixed (it's good to have a positive self-image, but accepting your extra weight may take years off your life), the truth is that the effort has failed.

While there is anti-fat bias in the media, anti-thin bias exists as well: Celebrities such as Angelina Jolie, the Olsen twins, and Lindsay Lohan have been regularly mocked and criticized for their thinness. On late night talk shows you are far more likely to hear a joke about how thin Nicole Richie is than a fat joke about how heavy Queen Latifah is.

Ideals of beauty change somewhat over time, but the simple fact is that proponents of plus-size preference have failed to convince America that fat is beautiful. They have tried for years to make fat as sexy as thin. It's no secret that thin people are considered more attractive than fat people.

But thin will always be in, for a few simple reasons.

Supply and demand

The first is simple supply and demand. This is pretty easy to grasp — things that are rare (whether diamonds, Picassos, or people with extraordinary sports ability) tend to be more highly valued than things that are common. In our culture (and in many others around the world), the vast majority of people are overweight or obese. Because the average person is overweight, thinner people are by definition rarer, and therefore more in demand. And the fatter our country gets, the more valued thin people will be, based on body shape alone. This isn't a value judgment of worth, it's basic economics.

There's also an evolutionary perspective.

At one point in our evolution, people who were heavier than average were prized as mates, clearly having access to food and resources. That is no longer true, and today obesity is instead a strong predictor of health problems; the person of normal weight is, on average, healthier than his or her overweight counterpart. All animals, including humans, choose partners partly (if subconsciously) on reproductive fitness: will this person be healthy enough to carry on my genes?

Note that this bias also works against very thin people. Men are less attracted to unhealthily thin women for the same reason. Studies done by researcher Devendra Singh show that when men are asked to rate the attractiveness of silhouettes of womens' bodies, they overwhelmingly pick the silhouette corresponding with the healthiest weight for women — not too thin, not too fat.

Of course, body shape is only one factor of many, and most overweight people find happiness and love. Being thin is no guarantee of being happy, attractive, or healthy. But, like it or not, there is — and always will be — an advantage to being thin.

Benjamin Radford is managing editor of the Skeptical Inquirer science magazine. He wrote about the media and pop culture in his book" Media Mythmakers: How Journalists, Activists, and Advertisers Mislead Us." His books, films, and other projects can be found on his website.