Clearly Kevin chooses to be much smaller than he used to be. Bodybuilders are not taken seriously in show business and you don't see anyone looking for another Arnold, Stallone or even Van Damme. Kevin's best chance to land roles is to appear similar to most leading men and supporting actors in size. If he wanted to make the occasional $600 day rate playing a bouncer who says, "I.D. please?", he could have gone that route and walked around sweating all year round at 240 lbs. in the LA heat.
He is a bit smarter than most give him credit for. If your goal is to be a bodybuilder, you seek to add muscle and get bigger. If your goal is to transform from a bodybuilder to an actor who gets to audition for something other than 'Burly Bodyguard' roles, you'd better lose that muscle and drop to a reasonable weight.
And as mentioned, at 5'9 and a ripped 205 lbs, Kevin still blows away 99 percent of competitive bodybuilders.