Originally Posted by
Torrilin
Calories in < calories out doesn't always work. The human body has a pretty weird metabolism, and has all kinds of tricks to prevent weight loss. Some medications will cause weight gain, no matter what you do. And some metabolic disorders (like diabetes) will cause similar issues. I would check with your doctor to make sure you don't have something unexpected like that causing trouble.
Controlled diabetes does not cause weight gain, weight gain causes diabetes.