Weight

I don`t know how big you are to start with, but for me a dress size is usually just twenty pounds. I`m a plus sized lady so, it might be different for your body.
Good diets - drink lots of water, fruits and vegetables and stay away from refined sugar - that alone will help alot.
If your really big, you might want to talk to your doctor about Zenical 120 - a fat blocking drug, it pretty much helps you to maintain a low fat diet but blocking fat from being absorbed into your body. (I`m on that now). It has some nasty side effects if you don`t watch how much fatty foods you eat, and most people tolerate taking just one pill a day with the biggest meal of the day - more than that and you live in the bathroom!