Lustig got 43 fat kids and gave them a low-sugar diet for nine days. The kids were eating a lot of sugar before - it constituted 28 per cent of their energy intake. Lustig got them down to 10 per cent (which still isn't 'low sugar' to real sugar fanatics, but never mind.) Their overall calorie intake supposedly remained the same as it had been before the intervention.
After the nine days, their weight had dropped by 0.9 per cent. Lustig takes this as evidence that sugar is uniquely fattening, or, as he puts it in the study, that 'the health detriments of sugar, and fructose specifically, are independent of its caloric value or effects on weight'.
There are a number of problems with this. For a start, as Tom Sanders says at the Science Media Centre, its violates the laws of thermodynamics. Since the degree of weight loss observed would require a calorie deficit of 630 calorie per day, it is more likely that the kids under-reported their usual diet. Kids, like adults, always significantly under-report their calorie intake. If they said that they usually ate, say, 1,600 calories when they really ate 2,200 calories then the 1,600 calorie diet Lustig put them on would be a weight loss diet with or without sugar.
Remarkably, there was no attempt to use a control group. This is such a basic flaw in the study that I'm surprised it was conducted, let alone published (OK, I'm not that surprised). Under-reporting of the usual diet would have been exposed if a control group had been given a calorie-controlled, high-sugar diet. Everybody would have lost the same amount of weight.
Lustig tries to justify the lack of control in the study, but his excuses are laughable. He says that 'if subjects under- or over-estimated their baseline fructose consumption, then providing them their reported daily fructose content would be problematic'. It certainly would have been problematic (for Lustig) since anyone who under-reported and was given their 'usual' high-sugar diet would have lost weight, and wouldn't that have been awkward? Lustig also makes a risible appeal to ethics, saying that 'maintaining fructose at the same level, even within a study, is commensurate with the message that the change in macronutrient composition is important for their health, and in order to use the study as an “educational moment.”' Give me a break.
There's a simple way to conduct a study like this. Give half the kids a 2,000 calorie per day diet that is high in sugar and give the other half a 2,000 calorie per day diet that is low in sugar. Make sure they eat it (don't just send them home with it, as Lustig does) and see what happens. I'll bet you the second law of thermodynamics that there's no significant difference between the two.
The part of the study that tickled me was the content of the low-sugar, weight loss diet that Lustig put these youngsters on:
This “child-friendly” study diet included various no- or low-sugar added processed foods including turkey hot dogs, pizza, bean burrritos, baked potato chips, and popcorn that were purchased at local supermarkets.
Hot dogs, pizza, burritos, crisps and popcorn! Has Lustig told his good friend Aseem Malhotra about this miracle diet? Malhotra first appeared on the scene railing against 'junk food' in hospitals. Admittedly, that was in the days before he jumped on the anti-sugar bandwagon so maybe he's in favour of hot dogs and pizza now. It's difficult to keep up with his ever-changing views.
It shouldn't be surprising that people can lose weight eating 'junk food' so long as they create a calorie deficit. This guy lost 56 pounds eating nothing but McDonalds because, whatever the cranks might tell you, a calorie is still a calorie.