Many men get tripped up by copying the diet of their favorite bodybuilder or hypertrophied action movie star. The problem? Well, most men don't have the genetics of a pro, they don't do the marathon workouts of a pro, and they're not using the drugs the pros are using. Heck, even guys on steroids probably aren't using a tenth of what the pros use.
All of those things add leeway to the diet. The pros can get away with crazy diets (at least for a few years) because of the drugs. You can't. Follow their muscle gain diets and you'll get fat and wreck your health.
Worst case scenario, you develop anabolic resistance: the impaired ability to build muscle caused by excess calorie consumption over time. It starts with insulin resistance, segues into leptin resistance, and when full-blown it manifests into excess fat gain, loss of the "pump" when training, stagnated strength gains, inflammation, and even low libido. Losing the excess fat after each mass phase gets tougher and tougher, too.
Follow the pros' fat loss diets and you'll lose muscle and wreck your metabolism, at least when doing it without the same chemical assistance they use.
Paying for Problems
Sadly, many competitive bodybuilders and internet diet gurus make a living selling their dysfunctional diet plans to googley-eyed fanboys. And those customized meal plans they sell? Usually they have three or four minor variations of the same plan and they just email you the one that's kinda sorta close for you. It's far from "customized."
Take the diet advice of pros with a grain of salt, or at least a couple of grams of test. You might be able to pick up a few tips from these guys – many are actually pretty smart – but remember that their plans are just that: THEIR plans. Not yours.
Your body is your laboratory and you'll need to conduct your own diet experiments to find out what works for you. That requires some thought and some work. Don't like that? Then keep paying someone else for the privilege of being their diet-bitch. Ignorance is expensive.