I think they are probably aiming at the wrong target, and that sugar is a bigger issue. I'm in favour of Governments taking a harder line in regulating the processed food industry, but taxing fat is insufficiently discriminate and seems unlikely to work.
We should do something about the food producers, though. A few years ago I knew an eminent public health professor in the UK who was a member of a committee advising Ministers on food industry regulation, they advised issuing guidelines that would reduce the amount of salt in various foods. That advice was rejected after lobbying from the meat industry. Bacon was 15% salt, by weight. Salt is cheaper than pork. Reducing the salt content would have meant the customer got more meat per pound of product, and either the price would have risen or the profits would have fallen. And we couldn't have that, could we?