They already prevent advertising the sorts of foods that contribute to obesity to children, and encourage you to drink less sugary drinks by applying tax to them (though unfortunately manufacturers have responded to this by reducing choice and adding artificial sweeteners instead of selling something at a higher price that can be enjoyed once every few weeks.

I don't think any of this is unreasonable in a country that picks up the tab through both subsidised dental care and completely free-at-point-of-use healthcare.

Unlike food, nicotine is not a necessity. Also calorie intake alone doesn't determine weight gain or loss. The problem of obesity is much more complex.

Governments try to address this problem through education and regulation of food. There are drugs available now to help control obesity and they're very popular, so people obviously want to avoid the condition.

I don't know why you think people should have a right to take highly addictive drugs that result in premature death. Contrary to smoker's claims, cigarettes are pure addiction and provide no benefits whatsoever to the smoker.

No but you can make sure only healthy desserts are being sold. You can only stuff so much carrot cake.

Decent labelling could be a start. Even when shopping online there's basically next to 0 of actual data of what goes into product.

Forget trying to create a healthy shopping AI agent.