Dear Briana, Welcome to Healthcaremagic!
Now a days every one wants to loose weight & you want it to decrease it by over a half! It's difficult but not impossible. You must first understand that there is no magical remedy/ or drug for weight loss
& it should be through behavioral modifications so that weight loss is maintained in long term. There are 2 basic methods:
1) Decrease calorie intake
2) Increase calorie consumption
OR still best-- COMBINATION OF THESE TWO.
I personally prefer & advice you to consult a nutritionist first for a proper long-term diet chart so you donot suffer dietary deficiencies. Anerobic exercises are good for calorie consumption & fat loss.
I again repeat that it will be safest method but it shall also require lots of will power.