How many calories you burn depends on how hard and fast you walk….
I  need to lose about 30 pounds and walking is the only activity that I can stick with. How many calories can I burn and can I really lose weight just by walking?
Walking is an easy way to burn extra calories to lose weight and decrease body fat. How many calories you burn depends on how hard and fast you walk, as well as how much you weigh. It is impossible to say exactly how many calories you’ll burn in 30-minute walk without your being measured in an exercise physiology lab. During a 30-minute walk, say, a 140-pound person burns around 127 calories walking at a pace of 4 miles per hour (or a 15-minute mile) and about 191 hiking on trails. A 200-pound person will burn around 182 calories walking for 30 minutes at 4 miles per hour, and about 273 hiking for the same period.
Research shows that a person needs to burn around 2,000 to 3,000 calories from physical activity every week to control body weight. That works out to be about 60 to 90 minutes per day. Shorter amounts, such as 30 minutes of walking, will improve your health, but are unlikely to lead to significant decreases in body fat or weight loss in a relatively short period of time.
If 60 to 90 minutes a day sounds like a lot of exercise, it is. But you can spread it out: little 15-minute bouts of walking throughout your day count, too. If you are regularly active and take the stairs instead of the escalator or pick a farther spot in the parking lot, for example, you can easily accumulate an hour of more of low- to moderate-intensity activity. Of course, if most of your activity involves sitting on a couch or in front of your computer, unless you are making a concerted effort to get up and move every hour, it may be hard to fit in a full 90 minutes per day.
Theoretically, 3,500 calories equals 1 pound of fat. So if you walk around 60 minutes per day, you can lose 30 pounds in about seven months. You can speed up the weight loss by making small calorie reductions in your diet for example, saying ‘no’ to regular desserts or using skim instead of whole milk).
If you are not yet fit enough to do a lot of exercise, take it one step at a time. Start with 10-minute sessions and add a few minutes per week.
Most important, wrap your mind around the idea that you need to be active for the rest of your life. Walking may melt off the weight you want to lose now, but if you stop moving once that extra heft’s gone, it’ll soon be back. Plus remember that every time you make your body move, you’re burning more fat and fine-tuning from the inside.