Whenever I visit a mall in Australia I despair at the long queues in front of the fruit juice vendors. I feel like going up to the teenagers in the queues and shaking them.

I don’t do it, of course, because nowadays one never knows how these young people will react. But I would like to warn them that fruit juice is fructose and fructose will make them fat and unhealthy.

As Robert Lustig, Professor of Paediatric Endocrinology at the University of California, San Francisco, says in his interview on the Health Report on the ABC radio programme, we are ingesting too much fructose and that has an influence on insulin which is the hormone whose purpose is to store energy. For “energy” read “gain weight”.

For years we have been told that fruit is good for us and for years we have increased our intake of fruit, or so we think. Actually our intake consists mainly of fruit juice or fructose additives, such as corn syrup. Professor Lustig says that the fruit in a piece of fruit is much better than fruit in fruit juice because a piece of fruit has fibre in it, while fruit juice has no fibre.

if we can cut down our ingestion of fructose, then our insulin levels will drop sufficiently to reduce our appetite and, furthermore, we will feel like being more active.

Obviously, I have simplified his interview and if you want the details then I suggest you go to the interview itself.

There are two important points that Lustig wants to emphasise which are fundamental to our health. The first is that food manufacturers put a lot of fructose into their products because the sweetness increases sales. He doesn’t believe that manufacturers intentionally want us to be come obese. They just want to increase sales and if fructose makes their products more appetising then that’s what they’ll put into them.

The second issue is that according to Professor Lustig the only way to combat the negative effects of years of eating fructose and other rubbish is through exercise. The following is a quote from him

The question is why does exercise work in obesity? Because it burns calories? That’s ridiculous. Twenty minutes of jogging is one chocolate chip cookie, I mean you can’t do it. One Big Mac requires three hours of vigorous exercise to work that off, that’s not the reason that exercise is important, exercise is important for three reasons exclusive of the fact that it burns calories.

The first is it increases skeletal muscle insulin sensitivity, in other words it makes your muscle more insulin sensitive, therefore your pancreas can make less, therefore your levels can drop, therefore there’s less insulin in your blood to shunt sugar to fat. That’s probably the main reason that exercise is important and I’m totally for it.

The second reason that exercise is important is because it’s the single best treatment to get your cortisol down. Cortisol is your stress hormone, it’s the hormone that goes up when you are mega-stressed, it’s the hormone that basically causes visceral fat deposition which is the bad fat and it has been tied to the metabolic syndrome. So by getting your cortisol down you’re actually reducing the amount of fat deposited and it also reduces food intake. People think that somehow exercise increases food intake, it does not, it reduces food intake.

And then the third reason that exercise is important, which is somewhat not well known, but I’m trying to evaluate this at the present time, is that it actually helps detoxify the sugar fructose. Fructose actually is a hepato-toxin; now fructose is fruit sugar but we were never designed to take in so much fructose. Our consumption of fructose has gone from less than half a pound per year in 1970 to 56 pounds per year in 2003.

I have written before on the need for more physical exercise in schools and Professor Lustig’s expert knowledge is a welcome confirmation of my amateur views.