There is an easy way to figure out what percent is genetic and what percent is environmental.
Look at the percentage of obese people during the Great Depression of nearly a hundred years ago.
The genetics were the same.
Obese people were very hard to find.
Really?
There are many peoples who tend to be skinny as all get out, and those who tend to be fatty.
Certain Polynesian types, vs certain African tribes.
It’s an adaption.
Many years ago there was a thread on this very subject. The poster pointed out that years ago people were much thinner and he posted a link to a youtube video of kids dancing on Soul Train. I don’t remember exactly the video but here is one. You can see those dancers are thin! Go to any high school and you’ll have a hard time seeing any students who are this thin. Check out this video
https://www.youtube.com/watch?v=0iUJzQ5svaE
BTW there is a fair amount of evidence that our school lunch programs have increased obesity rates dramatically.