20% fat tax to cut obesity

That’s what the headlines said. I felt I should check the original source myself.

It turns out to be a balanced and thoughtful study, reviewing all the research available so far.

The findings are difficult to contest:

• Small taxes will have a small effect.
• Big taxes might have a bigger effect.
• Broader unhealthy taxes and healthy subsidies could work better.
• There is not enough evidence of direct, significant and beneficial impact so far.

Some of the previous research it summarises seems seriously unreliable.

For example, a US study found that “a 35% tax on sugar sweetened drinks … led to a 26% decline in sales.” But the sample was a single canteen and there was no follow up to see if sales simply moved elsewhere.

More prominence was given to the finding that “US studies predict a daily reduction in energy consumption of 29-209 kJ per person for a 20% tax.” But even the highest reduction here is just 50 calories and it “assumed no substitution with other drinks.”

My own firm view is that:

• Nutrition policy should be incorporated into agriculture policy and education policy.
• Good public health requires good nutrition and good lifestyles.
• The right choices are better than the wrong taxes.

Further details are available from the British Medical Journal at www.bmj.com citing BMJ2012; 344:e2931 or from its lead author oliver.mytton@dph.ox.ac.uk.