I merged these two paleo-acne threads.

My acne improved immensely once I went LC, and it stays under control as long as I eat fairly cleanly.

Good food + insulin control + the anti-inflammatory aspect of LC (better fats, more omega-3s, little to no gluten) seems to improve acne.

There's a theory that anyone who's losing weight can be prone to acne, because fat tissue has a lot of stored crap in it. As the fat breaks down, the crap gets released and your face reacts by getting inflamed.