Hello, I too was once on depakote and had to go off of it due to the urge to eat and fast weight gain. My doctor said that is a side effect of a lot of mood stabilizers. I am now on lamictal and don't seem to be as hungry. I asked my doctor about switching to it because i had read good reviews on it. It may be something for you to look into. But as far as snack i would try to find something ligt like yogurt or rice cakes or nuts .
Generally any food that a person would ordinarily eat as a snack that would not promote weight gain or have a concern with sugar, calorie or cholesterol content. When I had this concern with medications I would eat flavored rice cakes. The other thing thats' important to understand is when a person takes certain medications their urge to drink water (and need water) can increase and its best to drink water instead of soda or juice that can have sugar. Also nutrasweet from what I have been told by certain psychiatrists (and experienced) is best avoided by people with bipolar or depression. If the weight gain becomes more than minor best to discuss this further with their psychiatrist and they could provide a referral to a nutritionist or adjust and/or change medications as needed.