I honestly don't know about the canned frosting. I know it's dairy-free, but I've stayed away from it because of all the additives and the high fat content. I think there is low fat canned frosting you might want to look into. Otherwise, here's a low fat chocolate glaze I found online!
Low Fat Chocolate Glaze
1/3 cup cocoa 2/3 cup powdered sugar 1 teaspoon vanilla extract 1 egg white 1 tablespoon water, or as needed
Beat together cocoa, powdered sugar, vanilla, egg white and water by droplets. Drizzle glaze over warm cake.