Whether you like it or not, Grant Gustin was not chosen to be the Flash in the growing DC movie universe. Instead, Ezra Miller will be suiting up as the super speedster in next year's Justice League Part One. And it looks like he's bulked up for the role!
Miller hasn't been in the public eye much lately, and in the time since we last saw him he went from being the skinny dude in the picture on the left above, to being the muscle-necked bro in the rust-colored jacket in the picture on the right. Granted it's hard to judge the magnitude of this transformation until he takes off a couple layers, but even like this he looks significantly different. Here are the full body shots for comparison:
Huh. Doesn't look like he's been skipping leg days, either.