Humans were not built to ingest large amounts of fast digesting carbohydrates in large quantities. When you consume excessive amounts of fast digesting carbs like white bread, candy, cakes etc you’re basically giving your body a ton of energy that it can’t do anything with. So what does it do? Stores the excess fuel as fat.
Good sources of slow digesting carbohydrates are brown rice, pasta, whole wheat bread, oats etc. These sources digest slowly and release energy over an extended period. Not only are these sources better for weight control, you’ll have more consistent energy throughout the day.