It might taste good, but sugar is addictive and fuelling the obesity epidemic, says Robert Lustig

Exploring the dangers of sugary food

Your lecture on sugar has been viewed more than 1.6 million times on YouTube. Why do you think it’s had so much attention?

The obesity epidemic just gets worse and people are looking for answers. Diet and exercise don’t work and the idea that obesity is about personal responsibility has come into question. Many people have said sugar is bad, but they didn’t supply the biochemistry. I supplied that.

Do you think fructose – which along with glucose makes table sugar – drives obesity?

I don’t think fructose is the cause of obesity, but I do think it is the thing that takes you from obesity to metabolic syndrome, and that’s where the healthcare dollars go – diabetes, hypertension and cardiovascular disease.


So the idea that “a calorie is a calorie” is wrong?

As far as I’m concerned that’s how we got into this mess. If a calorie is a calorie, the solution is eat less and exercise more. Except it doesn’t work. And the reason is that fructose is toxic beyond its caloric equivalent, so if you consume it instead of glucose you get more of a negative effect even if the calories are the same. It’s important that people recognise that the quality of our diet also dictates the quantity. In addition, “eat less” is a really crappy message that doesn’t work. “Eat less sugar” is a message that people can get their heads around.

Why do we consume so much sugar?

One reason is that it’s addictive. The food industry knows that when they add fructose we buy more. That’s why it’s in everything. There are five tastes on your tongue: sweet, salty, sour, bitter and umami. Sugar covers up the other four, so you can’t taste the negative aspects of foods. You can make dog poop taste good with enough sugar. In essence, that is what the food industry has done.

You say that sugar is a chronic toxin. Why?

We have three levels of toxins: things like cyanide where one part per million will kill you; arsenic and lead where 30 to 50 parts per million kills you; and toxins where high doses of thousands of parts per million can kill you. A lot of the last category are nutrients, for instance vitamin A, vitamin D and iron. Well, fructose falls in that category.

You think fructose should be regulated. Why treat it differently to vitamin D or iron, say?

The difference is that for vitamin D and iron there is no abuse potential. With fructose there is. We don’t regulate toxic substances that aren’t abused. We don’t regulate abuse substances that are not toxic, like caffeine. Where we get excited is where we have toxic substances that are also abused like cocaine, ethanol, heroin and nicotine. Well, fructose is a toxic substance that is also abused. By that analogy, we ought to regulate it.

Do you think sugar regulation will happen?

Obviously, no one is ready to do that. The question is how much more metabolic syndrome and diabetes do we need to see before we consider changing that policy? That’s a decision for policymakers, but they can’t make the decision without the science. I’m supplying the science.

Profile Robert Lustig is professor of pediatrics at the University of California, San Francisco. His lecture, “Sugar: The bitter truth“, explores the dangers of sugary food