John Cena, much like many humans, started life very small, in his mother’s womb.
Over the years, he grew an incredible amount. By his early teens, he was already much larger than he had been as a baby. It is likely he was a drug-free toddler; many others have made the same transformation naturally.
At some point in his teens (pretty early, judging by photos), John Cena started puberty and he grew taller, his frame filled out, and he grew a jaw that is larger than some small island nations. He was chock full of androgens, for sure.
He got interested in bodybuilding in his teens and briefly attempted a career as a bodybuilder. This is John, aged 18:
Image from Reddit
And this is from a show in his (very) early 20s:
Image from Reddit
Unfortunately this has already become an unhelpful answer, because that is not the physique of a 21-year-old who’s not taking steroids. I would guess he started at some point in his late teens.
Yes, John Cena had godly genetics, which is why he looked like a 30-year-old man aged 15 and a brick shithouse aged 18. But his physique is a combination of great genetics and steroids. (And perhaps other muscle-building substances like growth hormone.)
He’s been using ever since. I won’t pretend to know his cycle, or for what periods he is off and on juice, but he is over 40 now and looking more brick-shithouse-like than ever.
Image: Imgur
He is 250 lbs with abs at over 40 years old. I know there are a lot of mistruths about steroids and it’s a taboo subject for some reason, but John Cena is about as stereotypical a steroid user as it is possible to be. If WWE wrestlers had (strict) drug testing they would piss hotter than the Sahara during a heatwave.
But then pro wrestling would be boring, because it would be normal-sized men scrabbling around, instead of walking pharmaceutical lab behemoths battling it out.*
*Still not my thing, but whatever floats your boat.
There are lots of steroid users at every local gym. Some of them don’t even look like they lift. John Cena would probably look better than 95% of steroid users if he never juiced in his life, because he does have great genetics for muscle-building, and I have no doubt he ‘trains hard.’
But there are limits to what the human body can achieve naturally. John Cena has slammed those limits headfirst into the mat.