does the raw till four diet work?

Raw/fresh foods are always better than processed foods if you do it properly. If you don't do it properly them its one of the worst thing you can feed a dog. Luckily its easy to do it properly. They basically need around 80% muscle meat, 10% bone, 5% liver and 5% other excreting organs. Feed at least 3 different protein sources. There is a little more to it so do research first. You can start at any age. I have been feeding raw to a dog, 2 ferrets and 3 cats for over a year and none of them have ever had worms. Meat from the grocery store will more than likely not have worms. If you get wild animals they should be frozen for 2 weeks to a month to kill any parasites.

diets don't work,, why?

because a person needs to just learn how to eat healthy for life