Most men like to eat, and eat a lot. So it's easy to go too far with a calorie surplus when the focus is on muscle gains. But there's a difference between eating enough to fuel workouts, recovery, and hypertrophy, and eating so much that you just look like a fat guy with decent traps. Big arms don't count if three inches of that bigness is comprised of flab. And if you have a growing gut, it's safe to say that you've greatly exceeded the caloric surplus you need to optimally fuel hypertrophy. You're just layering on stubborn fat deposits, not building muscle.
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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, and soon you have that high-belly pregnant look that takes years off your life.
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Solution: Roughly a few hundred calories over maintenance is all you really need to fuel muscle gains. Think bodybuilding, not belly-building. Use targeted workout nutrition to add this extra fuel, not candy bars and fast food. Food quality matters. Those who say otherwise are selling ebooks and fantasies.