Diet represents the major factor underlying the development of acne. High glycemic diets with sugar, cereals, colas, fruit juice, bread, pasta, chocolate, and pizza lead to rapid increases in the blood level of insulin. Cells become resistant to normal levels of insulin and more insulin must be released to keep the blood sugar normal. Insulin-resistance leads to increases in sebum production (oily skin) that results in acne.
The solution is to eat a diet of animal protein and fat with occasional fresh fruit and vegetables and avoid all high glycemic foods and high fructose corn syrup. Caffeine will also worsen sugar metabolism and should be avoided.