Congrats on the weight loss. Medical reasons kicked off my current diet too--I was diagnosed with high blood pressure. South Beach sounds similar to what I'm doing right now. The first two weeks of no-carbs should have kicked your body into ketosis, and it will stay there as long as you keep the carbs down.
This really kicked me in the ass to drop weight. I did a fair bit of research into diets and really detested the idea of a fad type diet. But, for me - the South Beach diet allowed me to eat the food I enjoy and not feel like I was starving myself.
Fast forward to April 12th I had lost 42.6 pounds and had my blood retested. My triglycerides were down to 76 (a drop in over 300 points) and my cholesterol was down to 153. Granted triglycerides can range fairly broadly from day to day, but the doctor was very impressed with my progress.
This week, I started a morning exercise routine as outlined by the Hacker Diet ( http://www.fourmilab.ch/hackdiet/www/chapter1_2_5.html#Exerc... ). My goal is to drop an additional 25-30 pounds, which will get me to 170-175, over the next year by eating right and exercise.