No matter how much food I ate or beer I drank, I could probably never weigh more than about 210 pounds, and there are some people who could never weigh less than 210 pounds no matter what they eat or drink.
The laws of physics apply to everyone. However, I agree that some people are more inclined to be inactive (perhaps for medical reasons they can’t help) or to eat more (also possibly for medical reasons). But that doesn’t mean that will power and discipline can’t overcome those reasons, and those people can eat and exercise normally to maintain a normal weight.
Then again, there may be some people who excreting calorie-rich poo or pee, and these folks would be unnaturally skinny. However, it doesn’t work the other way.
Extremely heavy people are extremely heavy precisely because of what they do. When they liberated the concentration camps at the end of WWII, you didn't see any fat people.
I think ignorance accounts for most obesity. There isn't any way that you can eat a lot of fast food or junk food and remain healthy. Fat people are people who have developed the habit of eating garbage. Most of them then exacerbate that problem by avoiding any physical activity. And, then there are a lot of folks who reinforce those bad habits by pretending that obesity is some kind of a modern expression of human liberty rather than just ignorance and sloth.
Typically, obese people are ignorant people. Most of them wouldn't do that to themselves if they knew more about their alternatives. They shouldn't be encouraged to poison themselves.