Gauging from the Guardian’s article, reactions abroad are not uniformly negative. However, I think it’s a horrible idea.
First of all, not everybody is trying to avoid fat – lots of people are underweight, and some of us swear to Atkins when we want to lose weight – and why exactly should thin people and people on diets be punished by the tax system? Also, young kids are generally advised to avoid low-fat products (at least in the UK).
Secondly, the fat tax is too hard to apply, so to a large extent it will just make all products more expensive. For instance, here is part of a Danish article in my translation:
[...] A number of bakers in the North of Jutland have decided to distribute the fat tax on all products, including the low-fat ones. This means that the price of for instance a cream cake does not increase as much as the fat tax would otherwise have intended that they should.
“If we only raise the price of cream cakes, sales of them will grind to a halt. Therefore, we’ve chosen to spread the tax on all products,” says Preben Ramskov from Hjellerup Bakery.
The fact that the baker and the butcher can decide that the price of fatty foods should not rise as much as intended by the fat tax is confirmed by Tor Christensen from the Danish HMRC.
“They’re allowed to do that. They pay the fat tax on the goods they buy, but we do not interfere in how they distribute the price increase on the goods in the store,” says Tor Christensen. [...]
I totally understand that it would be too hard to require a baker or a butcher to calculate the exact fat contents of every single product in store, but if a tax is impossible to apply justly, it should be abolished. Alas, the new Danish government appears to be in favour of this stupid tax, so I guess it’s unlikely it’ll be abolished any time soon. I just hope it won’t spread to Scotland!