I am a Type 1 diabetic. I have just recently gotten into cycling. I did the South Beach about 5 years ago and again started in January. I am restarting the "Beach" now but in a different way. I am going to gradually change one meal at a time. Right now I am doing dinner. Most nights I eat chicken, mushrooms, zucchini and fresh spinach or I will make a really hearty salad. My numbers seem to be doing well with this and it has also cut out my late night snacking around 11pm.
As someone already mentioned its more about changing your eating lifestyle. I have about 25-30lbs still to lose and will go about this at a slower pace than shocking my body as I have previously done.