Simply placing a heavier tax on sugary/unhealthy foods is unlikely to actually change peoples eating habits, and just like the taxes on cigarettes, will end up placing an unfair burden on poorer people (since they tend to have less healthy lifestyles).

If you make unhealthy foods more expensive the people that already eat them will continue to do so, they will just eat less of them. Which isn't really a healthier option. We always talk about obesity but I remember reading somewhere (sorry for being vague) that the number of children in the UK being treated for malnutrition and even diseases like scurvy is skyrocketing.

Why? IMO it is because eating habits are something that are very hard to change. People that are used to junk food will crave it. Junk food is so easy to prepare and people tend to have busier lifestyles these days. Plus the fact that cooking skills haven't been passed down to the current parenting generation. Not to mention that its much easier to go to the supermarket and do one big shopping trip and store lots of junk away in the freezer than it is to make daily trips to the local fruit & veg store/butcher/fishmonger (and such places often don't exist in many towns).

We have a whole culture that makes eating unhealthy 100x easier than eating healthy. Heavier tax isn't going to change that and it would be a really unfair burden to put on people at a time like this.

Now of course I know something still needs to be done because it is a real problem. I'm not sure I have any good suggestions but providing healthier school meals seems like it would be a good start. Lunch is one of the two big meals a day so that would mean that right away all children would be getting 50% healthy meals five days out of every seven.