I'm 6 foot, 185 lbs but I've been as fat as 234. When you stop eating sugar and deep fried anything, the weight comes off pretty easy. The shocking part is how ADDICTIVE certain foods can be! I went through a weeks worth of headaches detoxing from all that garbage.
When I was in school there were maybe one or two fat kids. Now it seems AT LEAST 50% of the kids are obese and many are just plain chunky.
Alcohol is addictive too, yet most people don't become alkies. If the alkie wants to blame the booze so be it. Life is about choices. I've eaten little fast food over the decades and always regretted it when I did. I felt like crap.
I doubt they put in an additional addictive substance to get you to eat more, the fats, sugars and salt are what do it. Made for taste, not nutrition. But many (most?) Americans eat for sport, not fuel.