Make no mistake. Antoine is a freak. Maybe not as big as some of the guys out there, but he is a big dude, much bigger than many of the golden era guys. What makes him differnet is the small waist line. A lot of this is genetic, because I'm sure he is doing the same things everyone else is doing. Some guys are more prone to getting a big stomach, while others are not. Guys with a longer torso are more likely to have a smaller wiast. Often guys with higher lats are more likely to have a smaller wasit. Part of the distention now days, I believe, is due to the amounts of food guys are eating. Bodybuilders today are much bigger than they were years ago. It takes more food to be that much bigger and this food will push your stomach out, when you are shoveling tons in, each day. Some guys are going to respond better than others and not need to power shove while most are going to have to eat way way more than most people could imagine. I have seen some distention from insulin use and I'm sure this is part of what is causing the look we all see and dislike. In order for a 220 lb guy to get to 250, there is a chance it's going to require more insulin than your body produces, so insulin may be part of the program. 

So basically, these are issues of really big guys that are trying to reach the next level and be huge. This isn't going to be as much of an issue for smaller guys. I've seen a lot of smaller guys taking a ton of gear and GH, but you never see a light weight bodybuilder with a "growth gut". It's always the really big guys. Watch your body as you progress and keep the gut in check. If you are eating a ton and it's starting to look bad, maybe you need to dial it back a little or change your food choices up. As for anabolic steroids, I wouldn't expect much issue