So easily said, but not as easily done.

Some people live for exercise. For example, my ex was one. She was able to, for the most part, keep her addition to exercise in check by starting an exercise studio. When she didn't get to exercise, she was a butt. Others live to hike, ski, swim, and so on.

In the end, it boils down to personalities. That is, the mind.

Some may have had exercise drilled into them and just continued on. But many abandoned it. Consider all the hogwash schools push. In reality, much of the exercise they claim would help kids learn to stay healthy has no real play in reality. In fact, it, often, is laughable compared to what a farm kid does on a regular day.

In the end, success at keeping weight down, or taking it off boils down to mindset. Many strike out for help from exercise studios and such when they would be better served by finding someone to help them change how they think. A qualified hypnotist being a good possibility.