It definetly depends how addicted you are to sugar and fast-food. People who eat fast-food and drink pop everyday should definetly aim at cutting it out a few days out of the week to start. I think the majority of the population knows this is not healthy for you and probably only eats like this rarely. For me I had to go cold turkey for sure, I really wanted to rid my body of all junk once and for all.

So, I guess to answer your question if people are not committed to their health then yes convincing them to at least stop drinking pop is a step in the right direction. However, for most people to commit to a life-changing diet they must go cold turkey on sugar!!