diet plan, you maybe be building muscle, which could account for the weight gain
. Although a pound is a pound, muscle is denser than fat, so as you burn fat and gain
muscle, it's possible for your weight to increase for a time.
Another thing --- this one is most likely -- your diet plan may be cutting calories TOO MUCH and your body could be thinking that there isn't going to be enough calories, so it hangs on to what's already there.