There is a bit of a debate on how much diet impacts acne, but scientist’s have discovered that eating dairy and high-glycemic foods affects hormones that increases oil production in the skin, and thus may contribute to acne in certain individuals. White bread is an example of a high-glycemic food because it can raise blood sugar, leading to more inflammation and other problems throughout the body. Foods with a glycemic index of 55 or lower are considered a low-glycemic foods. You can find a database for foods and their glycemic index ratings at:
So if you have trouble with acne, you might want to try altering your diet. If your acne is severe, I would definitely recommend going to a dermatologist though.