Building Your Own Diet Plan

I’ve been on the South Beach Diet for almost four weeks. So far, I haven’t lost anything. I’ve been working out on the treadmill everyday for a maximum of 300 calories. Then I do 3 sets of curls (10 a piece) and 3 sets of situps (also 10 a piece). I have adhered to this diet, and I have not cheated. Last week, I bumped up to phase 2. The only things I’ve introduced are oatmeal and fruits. The weird thing is, about two years ago, I did this same diet and lost almost 20lbs in two months. Unfortunately now, I’m not losing anything. What gives? My current weight is 190, I’m 5′7, and I’m an even size 14. I’m 28 years old. Anyone have any ideas? And no, I’m not starving myself. I eat until I’m full, and this includes everything I’m allowed to have (ie lowfat meats, cheeses, eggs, etc)

i am on the south beach diet have been for 2 days im starting at phase 1 and i only want to lose 5 or 10 pounds im 12 years old almost 13 im 5 foot 0 inches and i weigh 90 pounds….will this diet begood?? will it help me or hurt me??