It is much more fun to go by how you look, how you feel, and how your clothes fit. It is wonderful. The emphasis is complete, low-fat meals every three hours, and one of the keys is to exercise first thing in the morning before breakfast. This forces the body to tap into the fat that is on you to do the work. Secondly, the program allows you to only do 20 minutes of cardiovascular workout every day.
Most people can do that.
If you are hyperglycemic, you may find it difficult to exercise before eating something in the morning. If so, try whipping up a meal replacement smoothie made with protein powder. It is an excellent book and an excellent program, and it works. In fact, I have done this exercise on many stations for radio aerobics. The first would be to squeeze the glutes.