Yes – sugar taxes do help reduce consumption of junk food

Are junk-food taxes effective? Yes.
Experience from Hungary and Mexico show that these taxes do drive down consumption of sugar-rich food, especially among people who eat a lot of it.
But is it enough to combat the obesity epidemic? No. Healthy foods also need to become more available, and a possible solution is subsidizing differently. Stopping subsidies of corn, wheat and soy (crops used intensively in junk-food production) would likely have a big positive impact.
Vox: Mexico and Hungary tried junk food taxes — and they seem to be working
Sugar
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From growing, (wheat, corn & soy) processing, packaging and distribution there are billions of dollars involved (thousand of stakeholders) and governments can not afford to shut or reduce the revenue stream.
It is for us to educate ourselves and make the right choices.