hmmm i wouldnt like to say that my reason is 100% correct but i can tell u wat i have experienced throughout my years....
whenever i go long periods of not eating something 'bad' and eating basic healthy 'diet' food, i can go for a while but then my blood sugar level drops (coz im not eating anything) and i feel larthargic with no energy.. then i find myself pigging out on wateva i can find!
not only is it because of my low energy levels, but because u r denying yourself of 'nice' foods as a result of hardly eating anything. i find it EXTREMELY rare to find a person who deep down truly does not like food such as chocolate cake etc, so when u cut them out complelety after a while u get sick of not eating them and u want it so bad u pig out...
my advice to you is in your everyday diet, include some 'nice' 'sweet' foods, but the keyword is in MODERATION- a healthy meal followed by 1 or even 2 biscuits, but thats it u kno.. or a healthy meal folowed by 1 small slice of cake..
its not this little moderation of food here n there thats gonna put weight on, its when u pig out, like u r now..
so my advice would be to just have nice sweet foods in moderation, then you wont have such low energy level and craving for this foods coz u cant expect to go perfect eating 100% of the time can u?!!