Scientists have proved for the first time that a cheap form of sugar used in thousands of food products and soft drinks can damage human metabolism and is fuelling the obesity crisis.
Fructose, a sweetener derived from corn, can cause dangerous growths of fat cells around vital organs and is able to trigger the early stages of diabetes and heart disease.
It has increasingly been used as a substitute for more expensive types of sugar in yoghurts, cakes, salad dressing and cereals. Even some fruit drinks that sound healthy contain fructose.
Experts believe that the sweetener -- which is found naturally in small quantities in fruit -- could be a factor in the emergence of diabetes among children. This week, a new report is expected to claim that about one in 10 children in England will be obese by 2015.
Previous studies of the potentially adverse impact of fructose have focused on rats, but the first experiment involving humans has now revealed serious health concerns.
Over 10 weeks, 16 volunteers on a strictly controlled diet, including high levels of fructose, produced new fat cells around their heart, liver and other digestive organs. They also showed signs of food-processing abnormalities linked to diabetes and heart disease. Another group of volunteers on the same diet, but with glucose sugar replacing fructose, did not have these problems.
People in both groups put on a similar amount of weight. However, researchers at the University of California who conducted the trial, said the levels of weight gain among the fructose consumers would be greater over the long term.
Fructose bypasses the digestive process that breaks down other forms of sugar. It arrives intact in the liver where it causes a variety of abnormal reactions, including the disruption of mechanisms that instruct the body whether to burn or store fat.
"This is the first evidence we have that fructose increases diabetes and heart disease independently from causing simple weight gain," said Kimber Stanhope, a molecular biologist who led the study. "We didn't see any of these changes in the people eating glucose."