Latest evidence suggests that internal fat, although invisible to the naked eye, is potently more harmful than external fat.

"Being thin doesn't automatically mean you're not fat," says Dr. Jimmy Bell, a professor of molecular imaging at Imperial College, London. Thin people can actually be fat at the same time, having a lot of internal fat stored around vital organs like the heart, liver or pancreas, possibly contributing to heart disease or diabetes.

Discovery was made through MRI scanning of men and women, who presented normal Body Mass Index (20 to 25). In as many as 45% of women and 60% of men excessive levels of internal fat were found. Lead researcher Dr. Bell, who named this people "TOFIs" (standing for ''thin outside, fat inside''), was not so surprised by his discovery: "The thinner people are, the bigger the surprise,'' he commented, as elevated levels of internal fat were found even amongst professional models.

Level of internal fat doesn't depend so much on the diet, but more on the amount of exercise. Therefore people, who maintain their slim figure without exercise, only through their diet, may have large deposits of fat inside them.

Deposits of internal fat can only be determined through an MRI scan, which is a rather expensive procedure. In contrast, even tough BMI may not be the most reliable tool, it is nonetheless far more practical and does give a relatively good estimation.

So can an overweight or obese individual actually be healthier than a normal-weight person? According to Dr. Steven Blair, an obesity expert, active obese individual can have a better metabolic profile than a normal-weight individual who leads a sedentary lifestyle. This means that an obese athlete like a sumo wrestler can in fact be healthier then his sedentary normal-weight spectator!

The good news is that inner fat deposits can be burnt off by committing some of your time to regular exercise. For cardiovascular health 30 minutes five times weekly is sufficient, but if you'd like to lose weight, 45-60 minutes on five days in a week is required. Don't forget about the healthy diet either. "Even if you don't see it on your bathroom scale, caloric restriction and physical exercise have an aggressive effect on visceral fat," an obesity expert, Dr. Bob Ross, claims.

"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," Bell concludes.

E.Z.