I always had very low bodyfat but I needed gear and alot of food to get big and strong. Real genetic freaks I believe can be big and lean and strong without gear and on very little food.
I had a friend when I was around 16/17 years old who was very skinny. He had come to the states from England and was pretty new around town.
I had been working out and already had a good physique for a highschooler. But with a very fast metabolism, I had to struggle for every inch of my gains, all the while consuming massive amounts of foods.
So my new friend decides he wants to work out too. He started with 11" arms, and within months he had 16" arms, then 17" arms around I'd say 8 or 9 months into working out.
This guy was shredded, fantastic muscle bellies, and all he did was drink beer, smoke cigs, and eat maybe 2 shitty meals per day.
Then he started steroids, and it was just unbelievable what he turned into..
The last I saw of him on facebook, he was pretty skinny, living in Australia as a beach bum. I had begged this guy to take up bodybuilding, but I suppose, easy come, easy go.