Dr Robert Lustig: a sugar tax is not about obesity, it's about diabetes

The man who penned the word 'sugar is killing us" has another set of telling phrases where a sugar tax* is concerned:


"All tax is regressive to an extent, but the poorer you are the more likely you are to drink sugary drinks and have tooth decay and be type 2 diabetic.


"People say sugar tax is regressive against the poor. What's more regressive, the tax? Or the diabetes?"


Robert Lustig

Dr Robert Lustig, American obesity expert and author of a number of books on the sweet stuff, including Fat Chance: The Bitter Truth About Sugar, and Sugar Has 56 Names says sugar is killing us and will bankrupt healthcare systems.


But he'd rather talk of sugar and diabetes than sugar and obesity for, he says, the correlation between sugar and obesity is weaker than it is with sugar and type 2 diabetes and when it comes to deciding on a tax on sugar "… it's not about obesity, it's about diabetes."


If we're looking to sugar taxes as obesity solutions, the beverage industry knows we won't find them, Lustig says in his interview with New Zealand's Stuff.


"They will do their best to talk about obesity, 'cause then it's calories in, calories out, balanced diet, diet and exercise. All their mantras basically stem from this notion of energy balance."


"It's not about energy balance, it's about hyperinsulinemia."


That's the medical term for when non-diabetic people get higher-than-normal insulin levels. 


"And that's specifically driven by sugar and sugary beverages.


"The evidence is a slam dunk."


Lustig and researchers at the University of California took "all the data in America" and looked at what effect a 20 per cent or 50 per cent reduction in sugar would have on lives, healthcare costs and diseases. 


A 20 per cent reduction would reduce annual direct medical costs for US adults by more than US$10 billion (2015 dollars) annually by the year 2035.


A 50 per cent reduction would mean healthcare savings of $31.8b in two decades' time.


So if we drastically chopped our sugar intake, how long would it take to see an effect on diabetes?


"Three years," Lustig says. "You would start seeing the change in disease three years after the reduction took effect."


It's backed up by an earlier study he did, which looked back in time over 10 years. It also found a delay of three years between changes in sugar consumption and diabetes prevalence.


Lustig says there is "hard causation" for sugar and type 2 diabetes, fatty liver disease, heart disease and tooth decay.


"Sugar causes insulin resistance. Insulin resistance promotes cancer progression. It's an easy jump to go 'sugar causes insulin resistance [and] causes cancer progression', but no-one has actually proved that in a prospective, causative model."


Jim Mann

Otago University Professor Jim Mann, who specializes in obesity and diabetes, says sugar should get some credit for obesity, because obesity and type 2 diabetes are so closely linked.


"It's extremely difficult to disentangle type 2 diabetes and obesity. There's very strong evidence to say intake of sugar increases the risk of obesity, and obesity drives type 2 diabetes.


"I might see 10 people with obesity and eight of them will have type 2."


Lustig is a childhood obesity expert and neuroendocrinologst based at the University of California, San Francisco (UCSF).


*Diabetes Queensland is advocating for a tax on soft drinks, along with a raft of actions including restriction on junk food advertising, setting food reformulations targets, mandatory Health Star Ratings, developing an active transport strategy and more to tackle growing obesity in  Australia.

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