Yes genetics is why a guy who has been doing boxing his whole life, a cardio intensive sport, has always looked like a blob......You really think is just his eating habits/hard work? LMFAO...Im sure there is people with worse eating habits/work ethic who are shredded/decent shape just by doing boxing alone, most people genetics respond to losing weight via boxing, really well.
Guy has worked hard his whole life and still looks like that(even if he took the rematch with AJ lightly, he has worked his ass off since he was a kid and he has always been obese)....it's clearly more than just food/work....it's ultimately genetics.
Going on a huge calorie deficit to lose weight quickly will make somebody feel "hungry"/"off".....This is a real thing, which is why bodybuilders feel like shit when cutting weight.......Em I saying that's what is happening to andy ruiz? No, maybe the calorie deficit isn't that drastic, but if it is, he could feel "off".