Blame the genes,

I went to a place called Johnny Rockets. While I was there, a huge couple sat in a table. When I say huge, I mean really really really huge.
My father said: -It's genetic. Do not judge them.
Me: -Genetic? They are about to eat a nasty hamburger.
Father: -It's there genes what makes them want to eat hamburgers.

I just wonder this, if you are scientist feel free to reply:
-What kind of gen is the "I want to eat nasty hamburgers?

For me it's just another justification for a wrong behavior.
"I am not a corrupt politician, it's my gens"
"I am not a sadist boss, it's my gens"
"I am not a crazy bitch, it's my gens"

If something needs to be justified, blame the genes.