Why do people gain weight after their 20s?

I am sure you know someone that in high school or college was the athlete in amazing shape. Years later in their 30s, 40s.... are overweight and unhealthy ! What happened ?????????
Let's go back as kids, most of parents assigned their kids in sports (soccer, ballet, swim etc...) They somehow manage to make sure they are active and healthy . Than there is school physical education classes keeping they active as well. High School , some are spending a lot of time doing their best in sports with the dream to be a professional athlete . College comes and the number goes way down on the physical activities . A few will continue on groups sports, some will join the gym. After their 20s , most get a job, maybe a family and the time to take care of their own bodies is not there anymore.
Did I get it right??????

I am not going to put everyone on the same boat, but not having someone driving you to do a sport, not having that teacher in school pushing, not having the dream to make it big being an athlete , not having the commitment is the problem!!! That's why a lot of people hire personal trainers these days, it's to have someone to commit to show up, be told they are doing a good job. It takes that "spark " inside to tell yourself JUST PUT YOUR SHOES ON AND DO IT! Yes, it's that simple.
The feeling you have after exercising is priceless. Everyone that exercises knows that!
Do yourself a favor today , make a commitment to yourself to be in shape, not only to look good but to feel good and to be healthy. The ones doing already.... GOOD JOB!!! Don't ever lose that "spark " in you.