Welcome to the diet thread. Congratulations on the 7.5kg loss. That's a good start.
But I have to say that the 'one meal per day diet" sounds like a terrible idea to me, and the idea that eating one item not on your diet (however you make your plan) means you should give up seems rather silly.
Sorry to be so negative, but I think that 'fad' diets aren't a good idea at all. For long-term weight loss you really need to make changes to your normal diet that you can just continue with. I'm not sure that only eating once per day is viable long-term.
The changes I've made to mine are to just eat a little less than I might have done in the past at each meal, and not to absent-mindedly snack on crisp/nuts/biscuits while reading. It is the latter that is hardest, but I just have to get used to not snacking while reading.
But if I do snack, I won't stop trying. A small snack while reading once or twice a month won't actually make a lot of difference. It's a small snack once or twice a day while reading that's the problem!