An experimental diet, for nine days, that cut out the type of sugar in soft drinks, fruit juices and most processed foods significantly reversed the buildup of liver fat in children and adolescents.

Contacted over the phone, Susan Noworolski, associate professor of radiology and biomedical imaging at the University of California, San Francisco (UCSF), said while the results are good for the kids studied, she did hope they could apply to a larger population.

Led by scientists at Touro University in Vallejo, California, and UCSF, the study examined the effects of a diet reduced in fructose, the sugar that is added to sodas and many snack foods, and found that liver fat decreased by more than 20 percent on average in this short time period, demonstrating a strategy to slow the spiraling global increase in chronic metabolic diseases.

"Such a significant liver fat reduction in just nine days of fructose reduction is unprecedented," said Noworolski, co-lead author on the study published Monday in the journal Gastroenterology.

The prevalence of fatty liver disease among adolescents in the United States has more than doubled in the past 20 years and is thought to cause a range of disorders by increasing insulin resistance, which dampens the body's ability to control blood sugar, leading to Type 2 diabetes and other metabolic diseases.

As sugar consumption among Latino and African-American teens is about 50 percent higher than that of Caucasians and Asians, the new study recruited obese non-diabetic Latino and African-American children and teens, ages 9 to 18. All study participants had at least one physiological marker for insulin resistance and they all reported habitual high sugar consumption.

Crucial to the research, the researchers found that participants lost very little weight on the diet - less than 1 percent, mainly attributable to water loss. The improvement in fatty liver, they believe, was not due to weight loss, as some scientists suspected, but specific to reducing fructose in the diet. The sugar fructose is plentiful in fruit juice and added to a wide variety of commercial food products. It is normally metabolized only in the liver, where much of it is converted to fat.

Unlike fructose, glucose, found in grains and some vegetables, is the body's principal source of energy. It is essential for metabolism and can be turned into energy in all of our cells.

In the experimental diet, the calories from fructose were replaced by glucose-rich, starchy foods. Calorie intake was designed to equal pre-study levels. Participants received a magnetic resonance imaging (MRI) scan at the start and end of the study to measure their liver fat. Over the nine-day diet, prepared meals were provided with no added sugar, so that the percentage of sugar in their food was reduced from 28 percent to 10 percent of calories.

As results, the researchers reported, in addition to the average reduction in liver fat of more than 20 percent, the participants' insulin sensitivity and other metabolic measures also improved greatly.

Noworolski said she is not working for the time being to further research in the same direction, but does hope some other members of the science community to continue the research.