Typically, to lose one pound, you must consume 3400 less calories than you metabolize, which means these people did about 300 calories of extra exercise a day. To put that in prospective,
here is a list of activities that would burn an additional 200 calories, so these people were probably doing about 45 minutes of jogging equivalent daily. The fact is, your resting metabolism is already quite high, as your body must maintain its temperature at a toasty 98 degrees; exercise only marginally improves on that.
On the other hand, losing 200 calories by dieting can drastically move that number from the low hundreds to even thousands a day for obese people.
Here is what 200 calories of food would look like... it almost doesn't seem fair that you would have to run for a half hour just to burn off a can of soda.
You want to lose weight? Try controlling portions to what the box recommends as a single serving. You'll quickly learn to value foods that satisfy a high fullness/calorie ratio, things like vegetables, soups, salads that fill you up faster. Also, track what you stuff in your mouth, it really helps keep you accountable.