February 11, 2009 4:53 PM

Doctors Warn Thin People May Be Fat Inside

(AP)  If it really is what's on the inside that counts, then a lot of thin people might be in trouble.

Some doctors now think that the internal fat surrounding vital organs like the heart, liver or pancreas — invisible to the naked eye — could be as dangerous as the more obvious external fat that bulges underneath the skin.

"Being thin doesn't automatically mean you're not fat," said Dr. Jimmy Bell, a professor of molecular imaging at Imperial College, London. Since 1994, Bell and his team have scanned nearly 800 people with MRI machines to create "fat maps" showing where people store fat.

According to the data, 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. "The whole concept of being fat needs to be redefined," said Bell, whose research is funded by Britain's Medical Research Council.

Without a clear warning signal — like a rounder middle — doctors worry that thin people may be lulled into falsely assuming that because they're not overweight, they're healthy.

"Just because someone is lean doesn't make them immune to diabetes or other risk factors for heart disease," said Dr. Louis Teichholz, chief of cardiology at Hackensack University Medical Center in New Jersey, who was not involved in Bell's research.

Even people with normal Body Mass Index scores — a standard obesity measure that divides your weight by the square of your height — can have surprising levels of fat deposits inside.

Of the women scanned by Bell and his colleagues, as many as 45 percent of those with normal BMI scores (20 to 25) actually had excessive levels of internal fat. Among men, the percentage was nearly 60 percent.

Relating the news to what Bell calls "TOFIs" — people who are "thin outside, fat inside" — is rarely uneventful. "The thinner people are, the bigger the surprise," he said, adding the researchers even found TOFIs among people who are professional models.

According to Bell, people who are fat on the inside are essentially on the threshold of being obese. They eat too many fatty, sugary foods — and exercise too little to work it off — but they are not eating enough to actually be fat. Scientists believe we naturally accumulate fat around the belly first, but at some point, the body may start storing it elsewhere.

Still, most experts believe that being of normal weight is an indicator of good health, and that BMI is a reliable measurement.

"BMI won't give you the exact indication of where fat is, but it's a useful clinical tool," said Dr. Toni Steer, a nutritionist at Britain's Medical Research Council.

Doctors are unsure about the exact dangers of internal fat, but some suspect it contributes to the risk of heart disease and diabetes. They theorize that internal fat disrupts the body's communication systems. The fat enveloping internal organs might be sending the body mistaken chemical signals to store fat inside organs like the liver or pancreas. This could ultimately lead to insulin resistance, type 2 diabetes, or heart disease.

Experts have long known that fat, active people can be healthier than their skinny, inactive counterparts. "Normal-weight persons who are sedentary and unfit are at much higher risk for mortality than obese persons who are active and fit," said Dr. Steven Blair, an obesity expert at the University of South Carolina.

For example, despite their ripples of fat, super-sized Sumo wrestlers probably have a better metabolic profile than some of their slim, sedentary spectators, Bell said. That's because the wrestlers' fat is primarily stored under the skin, not streaking throughout their vital organs and muscles.

The good news is that internal fat can be easily burned off through exercise or even by improving your diet. "Even if you don't see it on your bathroom scale, caloric restriction and physical exercise have an aggressive effect on visceral fat," said Dr. Bob Ross, an obesity expert at Queen's University in Canada.

Because many factors contribute to heart disease, Teichholz says it's difficult to determine the precise danger of internal fat — though it certainly doesn't help.

"Obesity is a risk factor, but it's lower down on the totem pole of risk factors," he said, explaining that whether or not people smoke, their family histories and blood pressure and cholesterol rates are more important determinants than both external and internal fat.

When it comes to being fit, experts say there is no short-cut. "If you just want to look thin, then maybe dieting is enough," Bell said. "But if you want to actually be healthy, then exercise has to be an important component of your lifestyle."

© 2009 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.
Add a Comment See all 14 Comments
by mahdeealoo May 13, 2007 11:15 PM EDT
I was very thin my whole life, but now, alas, fat has leaked out from the inside and landed right under my skin. I'm scared!
Reply to this comment
by hermit22 May 12, 2007 2:53 AM EDT
beanpoles beware.
Reply to this comment
by heresmy2cent May 11, 2007 7:51 PM EDT
The medical industry has become an incredible joke in America.

Thanks to lawyers and pharmaceutical companies, we have created the constantly heard mantra "Ask Your Doctor if (insert drug name here) Is Right For You." As if you are an idiot and are completely clueless about your own body.

The medical industry is being controlled by the marketing departments of big pharmaceuticals and large corporate medical providers. Their lawyers make sure they craft their endless disclaimers properly to attempt to cover their corporate rear ends when someone drops dead from one of their "remedies."
Reply to this comment
by extremophil May 11, 2007 6:22 PM EDT
If fat people are really thin on the inside, then I must be freakin anorexic.
Reply to this comment
by e7eryday May 11, 2007 5:41 PM EDT
I ate a thin person for breakfast- now I'm thin on the inside and out!
Reply to this comment
by xfredmenzies May 11, 2007 5:00 PM EDT
factchecker, since no names appear on any of the CBS news items, I just assume Ms Couric is the one in charge. The quality of the CBS news website has certainly gone down since she took over as the evening news anchor, and the number of morning show fluff pieces, like this one, has increased.

If the websites for the other news networks weren't so awful I would have switched by now.
Reply to this comment
by cathaleen May 11, 2007 12:28 PM EDT
Give it a rest! The diet industry rakes in billions of dollars every year by pounding it into people that they are too fat. Now there's
that fat person inside a skinny one. Bsssssss!
Reply to this comment
by heyitsme_76 May 11, 2007 12:10 PM EDT
Yeaahh..!! This means Kate Moss will soon be history..
Reply to this comment
by rohink-2009 May 11, 2007 11:14 AM EDT
may be fat on the outside, but I'm really very thin on the inside. Really.
Posted by incog-nito

That's funny.
Reply to this comment
by ccrcb44 May 11, 2007 8:00 AM EDT
Ya, fat between the ears!
Reply to this comment
See all 14 Comments
.
Scroll Left
Scroll Right More »
Better Information. Better Health.
CBS News on Facebook