Anybody have any thoughts on the following, particular the supposed need to
gain weight before healing can begin? Dr. Schwarzbein claims it is bad to
eat low to no carbs for a prolonged period of time and that eventually your
metabolism will slow down if you do this.

Taken from http://www.schwarzbeinprinciple.com/pgs/info/faq1.html:

"When you use up your biochemicals faster than you can rebuild them, you end
up damaging your metabolism. However, while you are using your biochemicals
it feels good. You have more energy, you can concentrate better and you lose
weight. Unfortunately, over time using up more than rebuilding causes you to
damage your metabolism. The only way your body knows how to heal its
metabolism is to rebuild its biochemicals. This is the opposite of using
them and you experience the opposite symptoms; fatigue, foggy brained and
weight gain. In hormone terms adrenaline and cortisol help you use yourself
up and insulin helps you rebuild. If adrenaline/cortisol levels are higher
than insulin you feel good while you are using up, if insulin levels are
higher than adrenaline/cortisol levels you feel worse as your body is
rebuilding or not letting you use up your biochemicals further. The SPII
program is designed to help people get through their transition without
feeling too badly. That is why there are individual programs for the four
current metabolism types."