Would taxing soft drinks lower rates of obesity?

Addressing the obesity epidemic by taxing sugary soft drinks sounds good in theory but it appears to fall down in practice. How could a taxation strategy be made to work?

Obesity is proving to be an intractable public health problem demanding innovative solutions and one idea that is attracting attention is the taxation of sugar-sweetened beverages. The theory is simple enough. Basic economics tells us that if the price of sugary soft drinks were to rise, their consumption would fall; lower intake should mean lower calorie intake which would lead to lower body weights. But would it work in practice?

The Ohio experience

A recent research study conducted in the United States provided some interesting insights. Taxing soft drinks has a long history in the US and occurs in many states today, though historically the rates have been low and the purpose has been to raise revenue. But there was an interesting exception. In 1992, the state of Ohio introduced high taxation of sugary soft drinks which was then repealed at the end of 1994. This provided an opportunity to test the effect of taxation of soft drinks on body weights over a period of two years. The researchers compared changes in body weights in Ohio over this period to (1) all other states that had no increased taxation and (2) a bundle of states with the same mean BMI as Ohio. The researchers found:

… very little evidence that the large tax imposed in Ohio had any detectable effect on population weight … our results cast serious doubt on the assumptions that proponents of large soda taxes make on its likely impacts on population weight.

How come? Why didn’t quite high taxation of sugary soft drinks affect body weights?

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Saturated fat: we still don’t get it

Although the headlines have got it wrong the science relating to saturated fat and heart disease has evolved considerably. But Australia’s public health nutrition policy makers are blissfully unaware and are implementing science that’s out of date.

In March yet another headline appeared in the mainstream media stating ‘No link found between saturated fat and heart disease’. The media delights in stories about diet that appear to contradict the status quo and, of course, relevant industry groups always put their public relations firms into action whenever an opportunity presents itself. Hence the misleading headlines.

Certainly there have been recent developments in how the coronary risk associated with dietary saturated fat is understood but it has to be said that the significance of these findings has still not fully registered with many nutritionists and policy makers in Australia, let alone the media. So let’s recap.

The way things were

Prior to 2009 many dietary guidelines around the world included a recommendation to eat less saturated fat on the grounds that it increased the risk for coronary heart disease. But there was always an unstated corollary to ‘eat less saturated fat’ i.e. eat more of something else. If your body weight is stable and you just eat less saturated fat you will start to lose weight, because saturated fat contains calories. To maintain weight while eating less saturated fat you have to eat more of other calorie-containing nutrients, such as carbohydrate, monounsaturated fat or polyunsaturated fat. So ‘eat less saturated fat’ really meant replace saturated fat with a healthier macronutrient.

The assumption of the old dietary guidelines was that it didn’t really matter what you replaced saturated fat with – it was thought that all replacements would lower the risk for heart disease. However, we now know that this assumption was wrong.

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