Follow a Good, Anti-inflammatory DietIn general, what you want is a nutrient dense, blood sugar stabilizing, anti-inflammatory diet that doesn't include anything you have an intolerance for. And you need to sleep well, keep as natural as possible circadian rhythm, manage stress and be physically active. This is not just for acne. It is anti-aging and good for everything that ails you. It can prevent conditions you didn't even know you were developing.
Keep all meals, drinks and snacks low to moderate glycemic load.It's the impact of the meal that matters, not each and every food. Never drink or snack on sugar without plenty of fiber and fat to lower the glycemic impact.
Eat real, whole nutrient dense food.Limit/avoid sugar, grains-especially gluten grains and refined grain products, hydrogenated/trans fats (margarine, crisco, most fried foods, corn & veggie oil). This means avoiding most commercially prepared foods.
Also limit dairy, especially unfermented and especially from cows. Milk contains hormones meant to make tons of things happen in a rapidly growing infant's body. This causes bad things in our no longer rapidly growing post-adolescent bodies.
The most anti-inflammatory foods are plant foods that are not grains and fish.Have lots of veggies, fruit, herbs, teas, and spices. Try to have only products from pastured animals as much as possible. High omega 3 fish like wild salmon, sardines, herring. Farmed trout is also ok depending on where it's from, but avoid farmed salmon.
The most inflammatory foods/meals are anything that spikes your blood sugar/insulin, anything you have an intolerance for, trans fats and high omega 6 sources like grains, grain oils, and products from grain fed animals.
Follow an elimination diet to determine any intolerances you may have.Either follow a very hypoallergenic diet for a couple months, then methodically add foods back in, or methodically eliminate foods starting with the most commonly problematic ones such as grains, nuts, peanuts, soy, eggs, citrus, shellfish, dairy, etc. Perfectly healthy foods could be causing your breakouts.
Try completely avoiding gluten grains and dairy for at least a month. And even if you notice no improvement, they should not be a big part of your diet. Dairy always affects acne for a number of reasons and gluten isn't good for anyone, causing serious harm for some people, and is usually part of some high glycemic food anyway. Grain products are empty or nearly empty calories. Don't fill up on them.
Consider Special Health Issues you may have.And then maybe you need to pay extra attention with supplements, foods and habits to address any issue you might have like gut permeability and other digestion issues, poor liver or adrenal function. Diet and lifestyle habits such as proper sleep,stress management and fitness level affect everyone's acne and can help everyone's acne. Some people just have to work harder to figure out what they need do.
For details on all of the above, visit my thread on this discussion forum where I've been participating for years: http://www.acne.org/messageboard/index.php/topic/230714-good-things-for-the-many-factors-that-lead-to-acne/