Overweight was once associated with age.  Apart from the occasional "fat kid" on the school-ground (the one that was usually standing while others were running or skipping) overweight was something that afflicted adults, as they eat ate even more they did at age 15,  drank alcohol, "didn't have time" for "physical nut" stuff like exercise and finally, avoided it because "it hurt."

I know what the writer's getting at with physical exercise being "natural" with the young, but this kid was no athlete.  I sat. Was a reader and TV obsessive, (LOTS of screen time) but when you grow fast and continuously, you burn calories just standing still.  My life-changing secret? Walking to and from school (at least 20 min. each way) five days a week for 12 years. Air cadet parade square drill sure helped ("lift those arms!")  The foundation for a lifetime of fitness. At age 70 I still walk and hike.

This also helped: very few desserts (which mom made), no pizza, and pop and candy very occasionally.