Pattana - I don't think you'd have an issue at all.
This "diet" is a lifestyle change. Since changing to it, I eat far, far better than I have in my life. Kale? Lentils? You've got to be kidding me! Now I adore them. SBD is basically healthy eating. Phase I long term is not healthy, since it has no grains or fruit, but some with a lot of weight to lose will do it a bit (1-2 weeks) longer. It does take commitment and prep, but after a while it becomes second nature and you learn a lot of short cuts.
Some phase I people lose 15 lbs. I lost 5 (I had 20 to lose). It depends on how much you have to lose, if you were truly committed, and just the way your body is. If I were you I wouldn't be surprised if you lost 8-10 lbs, but also not surprised if you lost more. But don't forget, it's mostly water weight from cutting out the grains, not true weight loss.
Seventy pounds is completely doable. Look at Lexxiss' (Debbie) profile, and she maintains well. There's some others, past and present, if you poke around. BUT, it will some work and definitely commitment. And you need to stick to phase 3 when you reach maintenance, because switching back to your old eating style won't work.
Oh- my hubbie had some bad bloodwork (triglycerides of 450 amongst other things), and I happened to be on phase I at the time, so dragged him in with me

. His bloodwork the next month - Trigly of 90!! Your body will love you
Good Luck!!
PS - support is the biggest thing. Make sure you stick around for tips and help. Nicole is our newest member, and we enjoy having her here! Hope you'll join us too! (Make sure you read the book....)