I've been told recently, that the best way not to end up in the yo-yo dieting trap is to aim for a weight loss of about 2lb/1kg per month. Also, to do it by making gradual and permanent changes to the way you eat/exercise, so that it becomes a way of life and not a 'diet'.
I was told that in an obesity clinic, where we had dessert on Sundays (some sort of pastry) and croissants rather than bread once a week for breakfast.
Although, if really stressed, I could hoover up an entire aldi-worth of chocolate, somehow I seem to have stopped doing it, especially if I eat more slowly and actually taste what I'm eating.
I've actually got nearly 12 stone to lose, and have an underactive thyroid that caused the weight gain, sadly so far not very well treated.
Once Christmas expense is over, our plan is to rent a rowing maching (a suitably sturdy one 
) and use their training/weight loss plan, and carry on eating a balanced diet as I did in the clinic.
In the clinic, no-one was on less than 1400 Cal/day, the majority were on 1600 Cal/day, and some of the men on slightly more ie 4 slices of bread per meal rather than the 2 slices for the 1600 Cal.
pm me if you'd like to know the things we were eating, as it was fairly simple, but varied. 4 course lunch and dinner, and bread, butter and yoghurt for breakfast.
The Paul McKenna way of eating is quite good - helps with relaxation, eating slowly and tasting food.