Stick to it for the first 2 weeks and see how you feel at the end of it
You may feel a bit crappy sometime between day 3 and 5 as your body adjusts to low carb intake then as your body goes into ketosis (fat burning mode) your energy should shoot up, also a big part of this is if you feel hungry then go eat something!
My blood sugar came under control in the first 10 days and it's been fine ever since, my blood pressure and cholesterol levels came right down within 3 months.
You should read the book thoroughly or start by going to the Atkins website.
Good luck.