Carbohydrates raise blood sugar and if you are eating cereal, bread or anything made with flour, potatoes, corn or rice, you will probably also gain weight in addition to having high blood sugar, particularly if you are not working out or exercising enough to counteract the effects of the carbs on your metabolism.
Insulin is a fat-building hormone and it's possible that it has added to your weight-gain along with the food you are eating.
Good snacks would be: nuts, cheese, celery, hard-boiled eggs, lettuce wraps (you take a large lettuce leaf and wrap in around a slice of American cheese or a piece of ham/chicken/baloney with a dab of mayo), yogurt (not with sugar, artificially sweetened).
If you change your snacking and go with these, your blood sugar would be lower and you would not gain weight.
I know it works!