There are some excelent snack advises here. One more thing to consider is whether you eat enough during your meals, because you should not need four snack a day. Perhaps try adding high quality fats and protein to make you feel fuller for a longer period of time.

I make the weight watchers bean soup and freeze it in 1 cup servings to pull out for a snack.
1 can fat free refried beans
1 can kidney beans, rinsed and drained
1 can black beans, rinsed and drained
1 can fat free chicken broth
1 can Rotel tomatoes
1 cup chopped onion
1 cup chopped green pepper
1 clove minced garlic
1/4 tsp. Cumin
Sauté onions and pepper in sprayed pan.
In a pot, pour the other ingredients, add onions and green pepper, bring to boil, reduce heat and cook for 10 minutes. Makes about 8 cups.

I love bean soup and that recipe looks good and easy. I might use regular canned tomatoes though because Rotel are too hot for me, even the mild version. Or maybe I will be adventurous!