Thin persons can no longer remain complacent assuming they are healthy as they are free from obesity.

British researchers caution that thin people may still be fat on the inside.

Dr. Jimmy Bell's team has conducted extensive research involving 800 subjects to establish that being thin does not mean one is not fat.

The study warns that thin persons may still be prone to risks due to internal fat gathering around vital organs.

The people who remain thin through dieting but without physical exercise are more susceptible to major internal deposits of fat.

Being lean, now researchers say, is no guarantee against diabetes and heart ailments. The fat enveloping internal organs send out mistaken chemical signals to store fat inside vital organs like the liver or pancreas. This could ultimately lead to insulin resistance and type II diabetes, or heart disease.

Even normal Body Mass Index (BMI) score is no indicator for acceptable levels of internal fat deposits .The findings of Dr. Bell's team are rather disturbing. Nearly 45 % of women with normal BMI scores had unacceptably high levels of fat. Among men the percentage was still more alarming at 60%.

A popular misconception, that a low-fat diet allows you to stay thin, spurred food manufacturers in America to produce a variety of processed, "fat-free" foods. But sadly, these processed diet foods often contained other fat-producing ingredients such as overdose of sugar, vegetable oils and refined flour that increase internal fat.

Researchers believe that thin people, who maintain their weight through diet restrictions rather than physical exercise, probably have major deposits of internal fat.. The good news is that internal fat can be easily burned off through exercise supported by regulated diet.

Amusingly, despite their uncouth looks, the super-sized Sumo wrestlers probably have a better metabolic profile than the slim, sedentary spectators. Dr. Bell claimed that the Sumo wrestlers' fat is primarily stored under their skin, not streaking throughout their vital organs and muscles.

Dr. Bell says "The whole concept of being fat needs to be redefined."

If one is obsessed only with physical looks and wishes to remain thin, then dieting alone should be enough. But if one is also keen to stay healthy, regular physical exercises are inescapable.