This is a general Problem !!
You are unable to maintain the balance between calorie intake and calorie Burn!!
Just take some high calorie intake in Morning , and in evening take only Low calorie high in protein diet (like Egg whites and all ) .
This will fix the issue !!
weight gain may be because of food substance remains after bowel Movement , it causing saturation and due to this weight is increasing !!
for articles relating your issue you can go to
Top Causes of Unexpected Weight Gain