Fructose can make you fatter

Fructose in the 'fat dock'

Foie gras is French for fatty liver. The delicacy, often sold as pate, is made when ducks or geese are force fed, causing their livers to fatten up as much as twelve times the normal size. However, what's shoved down their throats is not fat, but corn.

Pediatric endocrinologist Dr Robert Lustig of UC San Francisco Medical Center says he's starting to see fatty livers that look just like foie gras, not in ducks but in the bodies of overweight and obese children.

‘If you look at a kid's fatty liver, it looks just like pate,’ Dr Lustig says. ‘It's just got this glisteny white look to it, and you know it's not normal.’ The only difference between the kids and geese is that the kids do not eat corn, they drink excess quantities of soda drinks sweetened with fructose.

Fructose is found naturally in fruits and vegetables. But it's also found in many sugars, from cane and beet to high fructose corn syrup.

A century ago, Americans ate roughly three teaspoons of fructose a day, mainly from fresh produce; today they eat around 17 teaspoons of fructose a day mainly from processed foods and drinks. The average liver simply cannot handle that amount of fructose, so turns it into fat – and fatty liver disease can lead to cirrhosis, liver failure and even death.

Excess sugar in the liver also causes Acanthosis Nigricans, or a hyperpigmentation and thickening of the skin which, in overweight children, is a sign of excessive insulin, a precursor in many cases to diabetes.

The sugar and sweetener industries, unsurprisingly, take issue with the research claiming that the fructose in table sugar is biologically distinct from other forms of fructose and that these experiments used 100% pure fructose and that since we don't eat 100% pure fructose in our diets, these fructose studies are totally irrelevant to human nutrition. They also suggest that these studies will discourage Americans from eating fruits and vegetables, both relatively high in fructose.

Dr Lustig responds that, unlike processed foods, fruits and vegetables have fibre, ‘nature’s antidote to fructose’, which slows the absorption of fructose so the liver can handle it. Another antidote to fructose is exercise – if you don’t want your liver to metabolise it, burn it off with exercise. That's why the Michael Phelps of the world can eat 12,000 calories a day.

Read more or listen to Dr Lustig's full lecture on YouTube

First published in September 2009