Walking/Cycling for weight loss - calories burned

How many calories do people typically burn walking and cycling? How realistic can working these activities into our daily lives help people lose excess weight? I did a quick survey of an online guide to obtain some numbers. The calories burned through cycling, due to the air resistance increasing as the cube of the speed, is highly dependent on the speed traveled. Using the numbers given by the website above, and rounding to the nearest hundred calories (since the exact number varies due to many factors), we get in one hour's worth the following rough values. >

Speed (mph)	Man	Woman	Calories/mi (Man/Woman)
11 (slow)	500	400	50/40
13 (leisurely)	700	600	50/50
15 (moderate)	900	700	60/50
18 (fast)	1000	900	60/50

Now, at higher speeds, greater distances are covered in one hour. As for walking, we have the following. >

Speed (mph)	Man	Woman	Calories/mi (Man/Woman)
2 (slow)	200	200	100
2.5 (leisurely)	300	200	120/80
3 (moderate)	300	200	100/70
3.5 (moderately fast)	300	300	90/90
4 (fast)	400	400	100/100
4.5 (very fast)	500	500	110/110
5 (near jog)	700	600	140/120

Now, in order to see how many calories one can burn, say during a commute, let's suppose that a realistic commute time is 1 hour round-trip, which studies have shown people tend to gravitate toward regardless of the mode of transportation. Let's assume that a moderate rate is used, since we hopefully aren't racing to and from work on a typical day. A cyclist would then burn around 600-700 calories a day making a 6.5 mi one-way commute. Going by foot, the person would burn 200-300 calories on a 1.5 mi one-way commute. A 6.5 mi commute distance is quite reasonable for town/city dwellers; keep in mind that the distance from downtown Knoxville to north Knoxville is only around 3 or so miles. Walking (and cycling) can, if need be, be combined with the use of public transit for longer distances.

Now, how much is 600 calories? 600 calories are found in about 3.5 12 oz cans of regular (non-diet) soda or slightly less than two regular-sized McDonalds sandwiches. It is roughly a quarter of the calories in the diet of a "typical" man on a typical day. If, and here's the big if, someone can maintain identical eating habits yet commuted to work, one can see how gradual weight loss, or at least improved weight maintainence, is quite reasonable. There are numerous anecdotes of people who regularly ride who "never have to worry about what to eat." Endurance cycling events like those previously mentioned burn an incredible number of calories, with a metric century burning like 3000 calories and a full-century 5000. The caveat though is that it's tempting and quite natural to increase one's appetite when one regularly exercises; thereby reducing the weight-loss effects. Even if such occurs though, one would still be blessed with a healthier body overall.