Fast and effective way to lose weight?

I wanted to lose 20 pounds by December. I am already taking CLA (Conjugated Linoleic Acid) since August 9th, I take 3 a day. I know it takes about 3 months to see a difference. I work in a factory that requires me to walk my entire shift. I am thinking I walk at least 7 miles each day, plus heavy lifting and so on. I limit drinking Coke for only the weekends. I only eat half my suppers at work. I also eat fruit everyday, and drinking watered down ice tea or hot green tea.