Such foods are classed as having a high Glycaemic Index, or GI, and include white bread, white rice and highly-processed breakfast cereals. Examples of low Glycaemic Index foods are beans, vegetables, unprocessed grains and wholemeal bread. Weetabix and untoasted muesli have a moderate GI. Besides expanding the waistline, they may cause fatty liver - in which case, large globules of fat collect in the liver, causing it to swell. It raises the risks of liver failure.
In experiments carried out at the Children's Hospital in Boston, scientists looked at how mice fared when fed either a high or low GI diet. After six months on their diets, the mice weighed the same. But those on the high GI diet had twice the normal amount of fat in their bodies, blood and livers, the journal Obesity reports.
It is thought that the sharp rise in sugar levels associated with eating high Glycaemic Index foods drives up the production of the hormone insulin, which tells the body to make and store fat. Link