I have HAD mild back acne and face acne.
My face is really clear naturally (people think I wear makeup because my skin looks great) but I can break out when I eat these 3 things

1. Milk Products (milk and icecream) This causes the worst breakouts
2. food with red food dyes (this happens when I eat certain candies and juices) causes small but redish pimples that seem to never go away.
3. Too much rich dark chocolate and milk chocolate. This created a few pimples here and there.

So if I stay away from these products my skin will look super smooth and clear...no signs of pimples or acne at all when I am careful about my diet.