In a recent interview with E! Online, Nick dished on just how he got so buff. It definitely took a lot of hard work, as he explained, "I gained about 15 pounds of muscle for the role. I really wanted to look like an animal who internalizes a lot, but when he's in the cage and he's fighting that's when you see this kind of animalistic mentality that he has."
Still, he only held onto that animal look for a short time, as Nick explained he's lost 7 to 10 pounds of muscle since then: "The bulky muscle guy was probably good for a month or two, but I feel better where I'm at now."
You know his Jonas siblings had a little fun with him being so bulked up, as Nick said, "They were calling me the Hulk and they were poking fun at me a little bit."
via Source