Worried about your waistline? Hidden fat could be more dangerous than visible fat.

This holiday season, most of us will be overindulging in food and drink. After lavish turkey dinners, nights out at the pub and extra slices of Christmas cake, many people will be resolving to buy full-year memberships at the gym. Others may choose to repent by going on a diet so they can fit into their jeans again. But some recent research may be comforting - apparently appearances can be deceiving and the visible fat may not actually be as detrimental to your health as you think. The real culprits may be the hidden layers of fat, which could be present in someone who looks thin.

Professor Jimmy Bell, who works at the Medical Research Council at Imperial College, London, has spent years studying how humans store and use fat. Many studies he has conducted have shown that people who look thin can have large amounts of internal fat that are stored up around their organs. This hidden fat becomes clear when a person is put under a magnetic resonance imaging (MRI) scanner.

There are actually two types of fat: subcutaneous fat - the visible fat that sits under our skin - and visceral fat, which surrounds our organs. Bell claims that visceral fat has health risks since it is this type of fat that sends out chemical signals that can lead to diabetes and heart conditions. Sumo wrestlers, for example, may be spared from these health problems since most of their fat is stored under their skin.