I think I have an answer to your question. I have a holistic Acne book on how to cure Acne and it basically broke everything down into what they called an Acne equation. In order to have acne you need to have 3 things:
Medical research has shown that there is no digestive or liver funtion difference between people who do have acne and people who don't. The only thing that they have found is that people with acne have more sensitive oil glands then people who don't. This of course is genetic. But the thing is you have to have all three in order to get acne. If you don't have a hormone imbalance then you won't get acne and then same with the other two factors. Thats why some people can do whatever they want and don't get acne. But don't be fooled, that doesn't mean that they are not going to suffer in other areas. Their bodies will break down eventually or are already but it just isn't showing on their faces. Hope this helps.