"I put on … between five and 10 pounds (2-4.5kg) of muscle a year, and that came from all that heavy lifting (and) a lot of eating, a lot of eating."
His standard meal sounds filling in itself but Coleman repeated the dose six times a day — which severely impacted his sleeping patterns.
"It wasn't a lot to me but if someone normal tried to eat it, it would probably be a lot," he said. "So I'd eat a pound (450g) of chicken, grilled breast with half a cup of rice.
"I had about six meals a day.
"It's kind of hard to eat like that so I would have to wake up in the middle of the night to eat and go back to sleep.
"You kind of get used to it. When you eat like that, you get hungry every three hours. Every two or three hours you're hungry because I'm not eating a lot of fat. It's lean, I'm not eating a lot of carbs so it's a little bit of food at a time."
But Coleman's most incredible claim is the one that had Rogan questioning whether it was humanly possible.
In competition, Coleman — who only started lifting weights and competing to get a free gym membership — said his body fat percentage stood at 0.33 per cent. Rogan did a double take, perhaps thinking he'd misheard the 56-year-old.
So Coleman clarified.
"That's less than half a per cent," he said.
Rogan replied: "What? How does a human get that low?"
If you've ever measured your body fat percentage, you're probably thinking the same thing. But all Coleman could offer up as a reason for his ridiculously low reading was "genetics".
Coleman would usually give himself 10-12 weeks to prepare for a Mr Olympia competition. Three months out, his body fat percentage would have blown out — to three per cent — the highest it ever was while he was still competing.
To put that in perspective, it's generally considered acceptable for a male in their 30s to have between 20-30 per cent body fat.
It's obviously healthier to be on the lower end of that scale, while elite athletes would aim to be under 20 per cent at a minimum.
Getting down to 10 per cent means you're seriously ripped. Any lower than that and you're a physical specimen worthy of being studied by scientists.
Coleman blew those figures out of the water. No wonder the man was able to develop 61cm arms and a 150cm chest.
The bodybuilder said he was at his heaviest in competition during his seventh Mr Olympia win, when he tipped the scales at 135kg, but he got up towards 150kg during the "off-season".
Coleman may have been winning but there's such a thing as being too big, even in the bodybuilding world. His coaches, and even contest judges, told him he needed to slim down, so he dropped to 125kg before being dethroned by Jay Cutler in 2006.
But Coleman is a far cry from the man mountain who used to flex for a living. Now he can barely walk without excruciating pain.
Bulking up the way he did came with serious health problems later in life. Coleman has suffered serious back issues, had both hips replaced and endured multiple surgeries.
