I just wanted to share my story, I'll try to be as brief as I can. If it helps one person out, I'm happy.
How many times have we heard that diet has nothing to do with acne/zits/whatever ? Many, many times. I know hormones can play a huge role, stress, and other stuff... but for me, it seems to be largely diet related!
I was on antibiotics for years, the BC Pill, a low fat diet, topical stuff from the derm -you name it. They helped, but never was my skin this good. FINALLY!!
So I'm almost 41. And my skin is finally clearing up after changing my diet. The changes I have made:
Less carbs/Different carbs. Switched to Sprouted and Whole Grain breads and pastas. I try to eat nuts for snacks most times, instead of my old fave "baked Doritos" and other high carb/low fat snacks.
Cut out most dairy - I switched to Rice & Almond Milks instead of cow. Don't each much yogurt either. But I still love my cheese

I've heard that the hormones in milk products can cause breakouts for some.
Cut out most commercial sweets (candy bars, twinkies, cookies) - now I keep a big bar of good Organic chocolate in the cupboard; I also buy things like granola bars & other sweet treats that are made without hydrogenated oils, etc. I love my sweets!
Basically I try to avoid: Hydrogenated Oils, High Fructose Corn Syrup, Preservatives, Artifical Colors, and any ingredients that I can't pronounce.
Believe me, I still enjoy a pizza, nachos, a Twinkie. I never go hungry, and I still give in to cravings, just in different ways. I changed my shopping habits - shop in the "Organic" aisle, you'll be surprised at the yummy stuff! I buy the "All Natural" Cheetos and they are awesome.
Over the holidays, I ate lots of the chocolates, cookies, as well as other highly processed stuff - and my skin looked awful for the entire time.
I know this won't apply to everyone - but maybe it can help somebody who feels that they have tried everything else.
Take care!