Here is my comment:
As a child I was reasonably active with some athletic skills - I ran, played tennis and softball, did cartwheels, biked for miles at a time, and climbed trees.
I was also a little pudgy. Physical activity did not make me thin.
Other children teased me for being fat.
My parents tried desperately to make me thin throughout my childhood. I was on a skim milk diet when I was six months old. When I was older, I cried from hunger in the afternoons before dinner. I was not allowed to snack. None of this made me thin.
Today at age 45 I am very fat. I am convinced that my size is partly the result of ongoing food restriction in my childhood. Studies have shown that children who experience food restriction and hunger become unable to pay attention to hunger cues. Their bodies become super-efficient at processing food and storing fat. They are therefore at a much greater risk of becoming and staying fat as adults than children who are allowed to eat when they are hungry.
The MetroWest billboards of fat children, along with the hateful, scaremongering text, will frighten parents. Clearly, frightening parents is what you intend. Many people will respond by putting their children on calorie-restrictive diets. This will cause even more adults to become and stay fat in the long run.
Therefore, if you want to INCREASE the number of FAT adults and children, just keep running the billboards as they are.
If you want to IMPROVE THE HEALTH of adults and children, then get rid of these hateful billboards, and substitute information about staying active and eating well.