Thin people can still be too fat inside, doctor cautions
Use exercise, not diets, to maintain a healthy weight, experts say.
By ASSOCIATED PRESS
Published May 11, 2007
LONDON - If it really is what's on the inside that counts, then a lot of thin people may be in trouble.
Some doctors now think that the internal fat surrounding vital organs like the heart, liver or pancreas could be as dangerous as the more obvious 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.
Even people with normal scores on the Body Mass Index, a standard obesity measure, 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.
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.
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 send the body mistaken chemical signals to store fat inside organs. 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.