Perhaps a shorter summary of my preceding post. My suspicion (and that is all it is) is that you have never met a healthy Atkins person because those who are in the worst possible shape are the most likely to try it. Lots of skinny people do Ornish in an effort to get healthier and they can stick to it b/c it is clear that they have never had an insulin problem to begin with. Even in Atkins' book, most of his anecdotes are based on people who are incredibly unhealthy to begin with. A significant improvement for an Atkins practitioner may still seem unhealthy to you, but consider that the same person may very well be better off than on any other diet.
Again, this is why I feel it is necessary to compare how people are doing on a particular plan relative to their baseline, rather than to others (espectially athletes or very healthy others). Somebody singing the praises of Atkins may have just successully lost 70 lbs for the first time ever after many failed attempts, and his cholesterol may be significantly lower and he may feel great. However, we might still be looking at a 5'9" 230 lb person that still seems obese.