Children’s livers turning fatty
While it's known being overweight is a big reason for the rising number of children with type 2 diabetes, it's also increasing the prevalence of another dangerous condition: non-alcoholic fatty liver disease (NAFLD). This is a silent but dangerous epidemic. Just as type 2 diabetes exploded into our consciousness in the 1990s, so we at Children’s Hospital Boston think fatty liver will in the coming decade. Already it’s one of the most common yet least recognized complications of obesity – as many as one in three overweight children and one in two overweight adults have evidence of excessive fat accumulation in the liver. Fatty liver usually has no symptoms, but it can lead to hepatitis and sometimes progress to cirrhosis and liver failure.
Dr David Ludwig
We wanted to see if a high GI diet would cause fatty liver. Of course we couldn’t use children in such a study, so we fed either a high GI or a low GI diet to mice. The diets were equal in calories, fat, protein and carbohydrates. After six months on the diet, the mice in both groups weighed the same, but those fed the high GI diet had twice as much fat in their bodies, blood and livers. Our findings (published in Obesity, 2007;15) create a very strong argument that a high GI diet causes, and a low GI diet prevents, fatty liver in humans.
Here’s what happens. The glucose released into the blood after a high GI food ramps up insulin production, which tells the body to make and store fat. This process can be most dramatic in the liver because it is located just upstream from the pancreas, so concentrations of insulin can be extremely high in the liver after a high GI meal
A study on people living in Italy who ate high GI food showed they had fattier livers, but the study wasn't tightly controlled, whereas this study on mice shows that high GI carbohydrates can cause fatty liver in animals, regardless of other diet and lifestyle factors. We have now launched a clinical trial involving overweight children aged from 8 to 17 who will be randomised to either a high GI or a low GI diet. We hope to show that a low GI diet can reverse fatty liver in overweight children.
The current standard treatment for being overweight involves putting children on low fat diets, but that doesn't work for many children with fatty liver. Low fat diets could make things worse if they replace fat with high GI sugars and starches. Two low fat Twinkies, billed as a health food, contain the same amount of carbohydrate as an oral glucose tolerance test, which is used to determine whether someone has diabetes.
– Dr David Ludwig is Director of the Optimal Weight for Life (OWL) program at Children’s Hospital Boston and author of Ending the Food Fight