I lost 40 pounds and kept it off. I determined my resting metabolism - how many calories you use in a day. I them ate foods that had the same or lower calories. For example, if you use 2000 calories a day - make sure you consume less than that.
Also, eat like a diabetic. Only foods with a low glycemic value should be consumed. Raw fruits and vegetables, lean protein, nuts and seeds. Toss the grains in the garbage.
Supplement with chromium, CLA and GLA. (Oils that help burn fat.)
Most importantly - start lifting weights. Weight training every 3 days for 20 minutes is all you need to gain muscle. For every pound of muscle gained you will burn 50 calories at rest per day. Build ten pounds and that's 500 extra calories lost per day. (Much easier than running for 2 hours!)