This is what I found when I googled it:
Acne Diet - or Foods that cause Acne - acne diet
Reduce your intake of sugar (including excessive amounts of fruit juices), sweets, processed flour, baked goods, and trans or hydrogenated fats. Examples include donuts, cookies, pastry, ice cream, pies, etc. Use Stevia, the no calorie natural sweetener rather than sugar. Regularly eating breads, cakes, chips and other staples of Western culture is likely to promote acne.
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Sodas are a significant source of sugar. Switch to water, herbal teas, and vegetable juices. You can sweeten herbal teas with stevia.
Reduce intake of nuts, including brazil nuts, walnuts, almonds, and filberts. Peanuts and peanut butter may provoke acne in some individuals. If you eat nuts, limit your intake to small amounts and preferably eat raw nuts.
Reduce intake of milk products, including ice cream and cheese. There is a high amount of hormones produced in the milk of cows, particularly in the milk of pregnant cows, which makes up the bulk of marketed milk and dairy products. Milk from pregnant cows contains progesterone, 5-alpha reduced steroids, and other steroid hormones. These hormones, when consumed, can break down into dihydrotestestosterone (DHT), the final molecule that turns on oil-making cells. Studies show there is an association between milk consumption and acne, and it didn't matter whether the milk was whole, lowfat, or skim. For those who eliminate or significantly reduce milk products from their diet, calcium supplements could be helpful. Consider soy milk as a partial alternative. Buy unsweetened soy milk and sweeten it with stevia.
Reduce or avoid vitamin E supplements. I have come across some patients who have noticed acne pimples after taking vitamin E. I am not certain of this connection, but until more is known you may wish to stop taking high dose supplements of this vitamin. There have also been rare case reports of aggravated acne following very large intake of B vitamins.
Increase intake of foods that may improve acne such as fish (halibut, salmon, tuna, sardines). These contain important omega 3 oils such as EPA and DHA. They will make a difference in the health of your skin.
Eat as many vegetables as you wish, preferably organic. Eat a wide variety, not just the few that most American eat. The combination of fish and vegetables is likely to be the healthiest meal for those with acne.
Consider taking fish oil capsules if your intake of fish is fewer than twice a week.
Increase your intake of water. Drink a glass or two of cold water first thing in the morning to eliminate the bowels. Drink 4 to 8 glasses of water per day, more in hot weather.
Foods that I consider to have no major influence on acne include meats, turkey, and chicken.
http://www.raysahelian.com/acne.html
But I also found other sites for teens that say diet has no effect. My best advice is go with what got you results. If your diet helped, buckle back down. If you start noticing results again, then continue with your diet. I hope that helps!
Low Carb and Acne 
I really think it was my diet helping me clear up. Has anyone else had this happen? I hope it wasn't just a fluke, maybe if I buckle back down it will happen again!
