Snack tax may be more effective than a sugary drink tax to tackle obesity

The researchers say this option "is worthy of further research and consideration as part of an integrated approach to tackling obesity."

Obesity rates are increasing across the world. In the UK, obesity is estimated to affect around 1 in every 4 adults and around 1 in every 5 children aged 10 to 11, with higher rates among those living in more deprived areas.

The use of taxes to lower sugar and energy intake have mainly focused on sugar sweetened drinks. But in the UK, high sugar snacks, such as biscuits, cakes, chocolates and sweets make up more free sugar and energy intake than sugary drinks.

Reducing purchases of high sugar snacks therefore has the potential to make a greater impact on population health than reducing the purchase of sugary drinks.

To explore this in more detail, researchers used economic modelling to assess the impact of a 20% price increase on high sugar snack foods in the UK.

Modelling was based on food purchase data for 36,324 UK households and National Diet and Nutrition Survey data for 2,544 adults. Results were grouped by household income and body mass index (BMI) to estimate changes in weight and prevalence of obesity over one year.

The results suggest that for all income groups combined, increasing the price of biscuits, cakes, chocolates, and sweets by 20% would reduce annual average energy intake by around 8,900 calories, leading to an average weight loss of 1.3 kg over one year.

In contrast, a similar price increase on sugary drinks would result in an average weight loss of just 203 g over one year.

What's more, the model predicts that the impact of the price increase would be largest in low income households with the highest rates of obesity, suggesting that taxing high sugar snacks could help to reduce health inequalities driven by diet related diseases, say the researchers.

They point to some possible study limitations, such as the relatively short, one-year, time-frame over which weight changes were modelled, but say findings were based on information from high quality databases and remained largely unchanged after varying some key assumptions.

As such, they say that a 20% price increase in high sugar snacks, "has the potential to reduce overall energy purchased among all body mass index and income groups in the UK, leading to an estimated population level reduction in obesity prevalence of 2.7 percentage points after the first year."

"The results also suggest that price increases in high sugar snacks could also make an important contribution to reducing health inequalities driven by diet related disease," they conclude.

There is a strong rationale for using fiscal policy to improve diet and health, but caution is needed, say researchers in a linked editorial.

For example, they point out that substitution and displacement effects in response to food tax and subsidy policies are complicated and difficult to predict, while product reformulation in response to consumer demand can also have unintended consequences.

They also argue that fiscal policies aimed at reducing sugar, salt, and saturated fat intake "might be useful, but they fail to incentivise the consumption of healthy foods."

Ultimately, tackling obesity and diet related disease "requires close scrutiny of the social determinants of food environments and a systemic, sustained group of initiatives aimed at reducing health inequalities," they conclude.