AARP article on Walking

Downsize Me: Walk to Burn Fat
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Turn on the TV and you're bound to see an ad for a miracle weight loss gimmick. With all the pills and contraptions, it seems hard to know what will help us lose weight safely. But the answer really is simple: To rid yourself of unwanted pounds all you need are your own legs, some comfortable shoes, and a little open space.
Energy In, Energy Out
When it comes to body weight, remember this: 1 pound = 3500 calories. For every pound you want to lose, you must burn 3500 calories worth of energy. The only way to do that is to move more.
Walking is one of the best forms of exercise. It uses up oxygen, causing your body to burn stored fat. For example, you'll expend about 100 calories by walking a mile. That might not seem like a lot at first, but just think about it. Most people average just under 3 miles through the course of their day. If you add an enjoyable morning jaunt or a brisk evening walk you could easily move 4 miles a day. If you walk 4 miles 4 times a week, you can burn 1600 calories! That's half a pound of fat gone. Add more steps to your day while making sure not to eat more calories than you use, and your body can't help but trim down.
Walking also strengthens muscles, which tones and shapes your body. The increased muscle mass boosts your metabolism. This means you burn calories long after you stop moving. And you don't have to get all of your walking in at once. If you don't have time for long walks, find pockets of time throughout your day for short jaunts.
Maximize Your Walk
Any form of walking burns calories and improves muscle definition. But to get the most from your walk, concentrate on these main points:
Choose distance over speed. It's better to walk at a steady pace than walk too quickly and have to quit early. As your fitness level improves, you can speed up gradually.
Go for the hills. To help build your muscles, alternate inclines. Try walking up stairs, bleachers, or hills.
Warm up slowly. Walk the first few minutes at an easy pace to get your body prepared. If your start is too brisk, you risk burning only the immediate sugar supply in your body rather than the stored fat you want to lose.
Physical activity doesn't have to be hard to produce results; it just has to be steady. Walking lets you work your muscles and burn off stored fat. It's simple, enjoyable, and a good weapon in the battle against body fat.