Stick that treadmill in front of your favorite hour-long tv show and speed walk through it. Do this every day while sticking to your diet and you will lose weight.
And like misombra said, you have to sweat. If you're not sweating, you're not walking fast enough.
The working out may make you feel hungry at random times and you may get the urge to break your diet so try drinking lots of water throughout the day. Drinking lots of water is a really good way to curb hunger between meals.
