Dr. Jimmy Bell can be counted among those who believe that it’s what’s inside that counts. And now he can prove it. Bell’s team of molecular imaging experts in Great Britain recently discovered that about 45 percent of women and almost 60 percent of men may look thin from the outside, but internally these people — nicknamed TOFI ("thin outside, fat inside") — are packed with fat.

So how does this happen and what does it mean?

Bell explained to the Associated Press today that "people who maintain their weight through diet rather than exercise are likely to have major deposits of internal fat, even if they are otherwise slim." These deposits congeal around the liver, gut, heart, and other vital organs, putting TOFI at more risk for heart disease, diabetes, hypertension, and other conditions than people with visible love handles.

Even though the health of TOFI may be in danger, you probably won’t hear the Centers for Disease Control and Prevention (or food-police activist groups) ringing the alarm. Why? Because like many obesity researchers, they use only the body mass index (BMI) — a rough ratio of height and weight — to classify people as "obese" or "overweight."

But under this oversimplified system, athletes like Super Bowl MVP Peyton Manning and fitness experts like Governor Arnold Schwarzenegger are categorized as "obese," while the TOFIs go undetected.

Professor Bell’s work deals a great blow to the credibility of activist groups like the Center for Science and the Public Interest and the Physicians Committee for Responsible Medicine, which constantly point to an "obesity epidemic" to justify their lawsuits and proposed legislation. As Bell explains:

Obesity is a risk factor, but it’s lower down on the totem pole of risk factors … If you just want to look thin, then maybe dieting is enough. But if you want to actually be healthy, then exercise has to be an important component of your lifestyle.