Is there a diet that can help you lose about 20lbs. in 1 month, that isn't extreme like the Martha's Vineyard?

I want to lose about 20 pounds in a month...I have been exercising everyday (Cardio for 45 mintues and weight lifting) but I haven't seemed to shed any weight (Except for 5 lbs.) I used to be on a birth control shot (DeproVera) which caused me to gain about 40 pounds. I was 145 and now I am180lbs, I'm 5'5 and I'm 19 years old. I am considering doing the Martha's Vineyard Detox Diet but it's a little too extreme for me. I don't think I can drink vegetable juice morning, noon, and night for 21 days. Is there something else out there that has the same effect but not so extreme?