When I started walking 3-4 miles a day, I lost the last 15 lbs I was carrying around. The weight literally fell off! I used a Fitbit and coerced a neighbor to meet me at 5:30am and walk for an hour with our dogs. I'm now down to 115 lbs and ready for the summer!

I just started exercising again after a long period of sloth and weight gain. I have a physical disability so running isn't an option so I started walking and increasing pace and length every few days. I use mapmywalk which I really like. It's motivating and I can see progress. I recommend joining one of their challenges for motivation.

You might also consider introducing squats and lunges. I have bad knees too, but both exercises have really helped me; running no longer causes pain now that the supportive muscles are built up.

Oh, PP here again: you can too run when you are heavy (and over 40, I must say). I was and continue to be. Just start very slow - just do little bits of running (a minute out of every 5) to start out, and see how you feel. Work up slowly.

It isn't either or, actually. If you are walking to lose weight you have to do a lot of millage - my husband walks for exercise, and the other day he checked his fitbit, saw he had walked 14,000 steps and that it had allocated him an extra 100 calories. And his knees hurt. I run, but only 2-3 times a week and only for 2-3 miles. When I started running I walked most of the way, ran little bits. It took me about 3 months to work up to running the full 3 miles or so. The other thing I do is only run on dirt trails and my body is very thankful for it. And I think it is much, much more fun.