It seems that the whole concept of being fat needs to be redefined as scientists claim today that slim people could be fat on the inside and risk suffering from diseases such as heart disease and diabetes.

Researchers report that the internal fat surrounding vital organs such as the heart, liver and pancreas that are invisible to the naked eye may be as dangerous as the external fat that bulges underneath the skin.

For the last 13 years they have been scanning over 800 people with MRI’s (magnetic resonance imaging) to create "fat maps" showing where people store fat. The images showed that people who maintained their weight through diet rather than exercise could have major deposits of internal fat even if they are thin on the outside.

This finding shows that thin people may wrongly assume that they are healthy just because they do not have excess weight and actually risk their health by the attitude.

People with normal body mass index (BMI) have been found to have higher levels of fat deposits inside. They tend to eat too many fatty and sugary foods and exercise too little to work it off, which puts them at risk of becoming obese. Luckily, the internal fat can be easily burned off through exercise or even by improving your diet.

It has long been known that fat, active people can be healthier than their skinny, inactive counterparts.