The biggest factor in weight loss is food.  It's what you put in your mouth.  Exercise can help you lose and help with a ton of other health issues but the food you eat is the biggest factor.  In 2003 I was in a car accicdent & couldn't walk on a treadmill, ride a bike or do any workout without causing increased pain.  I gained 30 lbs. in 3 years.  In 2006 I joined Weight Watchers thinking it wouldn't work because I could not exercise.  Only changing what I ate, I was able to lose 37 lbs.!  If you can exercise, then do for all the benefits.  If you can't exercise, then make small changes to your diet and you will get where you're trying to go :)  I am happy to say I now can run/walk/workout.  My food choices are my problem and that is what I am working on now.