I (sort of) did it one day last week and found it really easy! I regularly don't eat breakfast, but will eat an early lunch around 11:30 to 12:00. But last week I had a hair appointment at 11, so I ended up eating my first meal of the day at 3:30pm. I found I was really hungry around noon, rumbling belly etc, but then it completely went away and I just felt good all afternoon - not even particularly hungry when I did eat at 3:30.
So my question is, does it 'ruin' the whole principle (physiologically I mean) of IF if you have a coffee in the morning with milk and sugar? I have one every day when I get up at 6:30, and honestly it's one of my fave 'meals' of the day - I SO look forward to a great coffee, but it has to be with the 'right' amount of milk, and sugar (not the same with sweetener to me).
Or, is IF more of a tool to control calories, and really is not dependent on how long between meals or whether there are a small number of calories taken in between meals?