Well I love Curves, but I don't think it does a thing for weight loss.
I have gone to Curves over 300 times (4 to 5 times a week). I have much better upper body strength, more energy and I feel fitter. However, I have only lost 5 pounds which is a huge disappointment! I don't eat junky, nor have I dieted ( you don't want to live with me when I diet!). Just try to eat normally and exercise regularly. I don't think the aerobic component of Curves is enough to really burn the calories.
I have met many people at Curves, of course, but the only ones who have lost noticable weight are the ones who do a diet plan. Some do the Curves diet, some do South Beach, etc. However the long timers really don't lose weight doing the exercise alone.
P.S. I am speaking about women in the 40 to 50 year old ranger. Younger women will probably do better!