My personal beliefs, is that we are teaching kids to fear playing outside.
Just think about it, you should lose as much as you eat by being active. The thing is, people are not being active enough; just like simple walking. Not to mention people don't drink enough water, because if your urine is not a light yellow, your dehydrated. People drink Colas, and Energy drinks with high sugar but not enough water to counter that sugar.
We teach kids you could be abducted, molested, raped, and murdered by men in cars. Back in the early nintys, my elementary school had ZERO cages to keep us in. We could run into the streets to grab the basketball, as long as cars were no passing.
No kids play outside after dark, and we teach kids that they are frail, and could die with a scratch. I remember playing on the jungle gym, playing American Gladiators like pull offs from 10-12 feet only to crash into the sand below.
If kids are not taught at a early age the meaning of fun, playing outside after dark, and eating healthy... then we tell them that eating fastfood over cooking lean meats is okay or we can video game for hours.
Although that is just me, but it's just our public fear keeps us inside and thus we don't play outside as much anymore to burn fat off.