The Ireland Journal fact checks claims about sugar taxes. They find:
Claim: Taxes on sugary drinks have not achieved their public health aims
Verdict: Mostly TRUE
There is some evidence that the tax precedes a moderate decrease in consumption, but also that this effect tends to fade quite quickly
There is no significant evidence that sugar taxes cut body mass index (BMI), or rates of obesity, diabetes or heart disease, but there is evidence that they have not achieved such desired and promised public health gains
However, most sugary drinks taxes were implemented quite recently, and subsequent research may yield different results as the effects of the taxes develop.
This is from a neutral observer. The full article is a very good read. A couple of extracts:
It suggests that, while it is possible the introduction of sugar taxes may have slowed those increases, the taxes certainly did not cause a single decrease in average BMI or obesity prevalence in 96 opportunities for that to happen (four countries, six years, two measures, two gender categories).
So what is the evidence that they reduce obesity:
It should be noted that several studies can be found which project a likely or possiblereduction in BMI and obesity, but this research is generally based on predictive models, rather than data gathered in the context of a tax having already been implemented.
The evidence is predictions, not evidence.
So when people argue in NZ for a sugar tax, they have no evidence at all they reduce obesity. It’s just a way to tax New Zealanders even more.