Cutting out the sort of sugar commonly found in soft drinks, fruit juices and processed foods reversed the buildup of liver fat in children and adolescents, a condition closely tied to diabetes and heart disease.
In a nine-day experiment, researchers from Touro University and UC San Francisco found that a diet with reduced fructose cut liver fat by more than 20 percent. Fatty liver disease in youth has more than doubled in the past two decades, leading to increased insulin resistance. That, in turn, reduces a person’s ability to control blood sugar, which leads to Type 2 diabetes. The findings were published in the journal Gastroenterology.
Said lead author Jean-Marc Schwarz: “Our study clearly shows that sugar is turned into fat, which may explain the epidemic of fatty liver in children consuming soda and food with added sugar. And we find that fatty liver is reversed by removing added fructose from our diet.”
Added co-lead author Susan Noworolski: “Such a significant liver fat reduction in just nine days of fructose reduction is unprecedented…. The results provide exciting hope for a strategy to combat the metabolic problems associated with fatty liver disease.”
The improvement in fatty liver was not due to weight loss, but to cutting out the sugar. Participants lost less than 1 percent body weight on the nine-day diet, mainly due to water loss.
Said Robert Lustig: “Many people think that fructose provides empty calories. But no, they are toxic calories because they are metabolized only in the liver, and the liver turns the excess into fat.”
In the experiment, calories from fructose were replaced by glucose-rich, starchy foods. Total calorie intake was equal to participants’ pre-study levels. Glucose is the body’s main source of energy, and is essential to metabolism and energy production at the cellular level. Glucose is found in grains and certain vegetables, and is metabolized in the liver where a lot of it gets turned into fat.
Latinos and African-American teens consume about 50 percent more sugar than Caucasians and Asians. In this study researchers recruited obese but non-diabetic Latino and African-American children and teens, ages 9 to 18 with at least one physiological marker for insulin resistance and high sugar consumption.
An MRI was performed at the start and end of the study to measure liver fat. For nine days, participants ate prepared meals containing no additional sugar, so sugar represented just 10 percent of total calories, down from around 28 percent pre-study. As a result, the average reduction in liver fat was more than 20 percent, while insulin sensitivity and other metabolic measures also improved substantially.
Said Kathleen Mulligan: “Such increases in insulin sensitivity potentially reduce the risk of diabetes and other disorders associated with the metabolic syndrome.”
The results are in line with a new model projecting that a 20 percent drop in fructose consumption would cut the prevalence of a range of metabolic diseases by about 5 percent and save $10 billion a year in medical costs. Reducing sugar consumption by half would cut disease save $32 billion annually.