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Britain is fighting childhood obesity with a new soda tax. But will it work?

The food revolution is underway

The food revolution is underway. This feels like a victory for Britain's children and for everyone who has campaigned so hard for a tax on sugary sweetened drinks. I would love the money to go to food education as well as sport but I think we have to applaud the Chancellor for taking this extremely important, bold step. I hope that this bravery will continue to form a part of this Government's attitude to dealing with obesity and will influence the Prime Minister's Childhood Obesity strategy later in the year.

Posted by Jamie Oliver on Wednesday, March 16, 2016

(Jamie Oliver's Facebook page)

This week, Britain's government became one of a handful in the world to introduce a tax on sugary drinks aimed at fighting childhood obesity.

Dancing outside of Parliament after the announcement, celebrity chef turned public health champion Jamie Oliver — who has long campaigned for this levy — lauded the move. He called it "bold, brave, logical" and said he hoped it would "ripple around the world."

Former New York City Mayor Michael Bloomberg, who tried and failed to impose a similar tax during his leadership, said the new policy "puts the UK at the forefront of the global fight to reduce obesity and diabetes."

But researchers who study sugary beverages and health say it's hard to know how well the tax will work. They don't expect the added cost to sugary drinks will drive down the UK's rate of obesity immediately. Even so, most think these taxes are a promising idea.

How taxes on sugary drinks work

In Britain, beverages will be taxed at two levels according to the amount of sugar they contain: Drinks with less than 5 grams of sugar per 100 milliliter will be taxed at a different rate than drinks with more than 8g per 100mL. So that means a 12-ounce can of Coke will get an 8-pence (11-cent) tax, according to the Economist, whereas Coke products with less sugar — like Coca-Cola Life — will be taxed at 6 pence (9 cents).

There's lots of evidence that high-calorie, nutrient-poor beverages such as soda have been major contributors to the obesity epidemic. They give people big, quick doses of sugar with little accompanying nutritional benefit or satiety. So the basic idea behind a sugary drinks taxes is this: Making drinks like soda more expensive through taxation might help reduce consumption, improve awareness of the health harms they carry, and nudge people to choose lower- or no-calorie beverages instead.

Other jurisdictions — like Mexico, Denmark, and even Berkeley, California — already have similar taxation schemes in place. They each work a little differently, but they share a common goal: Raise the price of sugary beverages to drive down the amount people drink and, in turn, reduce the rate of obesity.

There's little evidence so far on how much these drink taxes can impact health

I asked several researchers who are studying how taxes like Britain's may impact public health whether this type of policy can really reduce obesity.

It's hard to know that right now, since so few cities or countries have managed to get these taxes in place (often facing fierce opposition from the soda industry). But preliminary data from Mexico and Berkeley — where taxes have been implemented in the past two years — have documented declines in sales of sugary drinks. In Mexico, in particular, the reduction was greatest among low-income households — which also happen to be the groups most affected by obesity, according to a study published in BMJ in January.

But some researchers believe the taxes have real limitations in fixing a problem as complex as obesity.

For one, the taxes usually don't apply to all caloric drinks that people love. In the UK case, for example, pure fruit juices and sweet milk-based drinks, which can have just as much or more sugar as soda, won't be taxed. So consumers will still have options that are potentially cheaper, but still calorie dense, once the tax is imposed, said Roland Sturm, a senior economist and professor of policy analysis at RAND.

The tax is also pretty small. Sturm predicts that the added cost of 9 or 11 cents for sugary drinks in the UK will seem marginal — and inconsequential — for consumers who are already willing to fork out a couple of dollars on a beverage. "Don’t expect small taxes to make a big splash in reducing obesity," he said.

coke soda

Soda sales have fallen in recent years. (Graphic by Javier Zarracina)

Marion Nestle, a New York University professor who wrote the book Soda Politics, says it will also be hard to disentangle the impact of taxes from the overall trend in declining rates of soda consumption. In the US, for example, soda consumption has been dropping since the late 1990s. In Berkeley, "consumption rates were low to begin [much lower than the national average] ... so measuring a further decline won’t be easy," she added.

What's more, sugary drinks are only one source of added dietary sugar, and taxes on them haven't yet been linked to marked health improvements, said Shu Wen Ng, an associate research professor in nutrition at the University of North Carolina who co-authored the BMJ paper. "It will be a while before we expect to see health effects — like weight change, metabolic changes — as these changes require persistent changes over time to occur."

Ng pointed out that the obesity epidemic crept up slowly and insidiously. Reversing the trend will take time. "It will also take more than just an sugar-sweetened beverage tax," she said.

The taxes can be helpful in other ways

Even if soda taxes don't immediately change health, they do have other benefits.

First, they can raise awareness about the health harms of drinking what is essentially nutrient-bankrupt liquid sugar. "Taxes generate a vast amount of media discussion of the effects of sugary drinks on health," Nestle pointed out.

Taxes also help shift social norms, said Sturm. Consider tobacco: Increasing the price of cigarettes through taxation was one of the biggest contributors to driving down the smoking rates. "Smoking rates didn't drop immediately, and taxation had a small effect on consumption immediately," he said. But eventually the taxes had an effect, "and with fewer people smoking ... it becomes less acceptable to smoke, so it was a feedback loop." He said the same could happen with soda consumption.

The money raised from the taxes can be used to support other obesity-fighting policies. In Britain, revenue from the drink taxes will fund childhood obesity interventions, such as sports programs in primary schools, for example. In Berkeley, the money goes to children's health programs in low-income areas that are battling particularly high rates of childhood obesity.

The tax may also encourage companies to change their manufacturing practices by offering more lower- and zero-calorie options — a trend that's already started.

"While a sugar-sweetened beverage tax will not be a silver bullet, if it results in even more moderate changes in obesity, that would be very welcome by public health advocates," said Brian Elbel, an associate professor in popular health and health policy at the NYU School of Medicine.

And, he added, the tax may be just one of the many policy tools in the toolbox. Ng said she'd also like to see more regulation of how beverage companies market their products, to children and others.

There are also measures people outside of government can take to discourage soda drinking. Chef Oliver, for one, has been leading by example. He added a 15-cent tax on sugary drinks in his restaurants last year. The money raised goes to healthy eating education programs. As Elbel said, "We have to keep looking for policies that can have even small but cumulative impacts."