I agree that you can build muscle while in a calorie deficit. Of course, it’s not the best way to build muscle, but if you are using anabolics, it is definitely possible. And it happens very often. So with many things Kurt says I don’t agree, but on this one I do. However, is it optimal? No, it’s not optimal, because it’s not the fastest way to build muscle. You will never be really huge if you use this method. But I think you can look decent. Of course, it depends on what “decent” means to you. But you will not be a heavy bodybuilder or super heavyweight doing it this way.
But... everything is within context.
It seems as if people are using an extreme stance on pushing food and they're comparing it to those who eat closer to baseline. The extreme examples of people gaining more muscle by pushing food are likely guys who really have their shit together and are living a 365 day a year bodybuilding lifestyle.
What gets measured gets improved. This is the case for diet, training, and drugs.
Also, the law of diminishing returns.
Most bodybuilders who got huge by pushing food and getting soft were also very accountable at the beginning of their prep phases, giving themselves plenty of time to trickle off body fat to preserve their new muscle. It's likely that if they slowly pushed food, accounted for their macros, and didn't get as fat, they would have likely been just as muscular and needed less time to diet into a show. It's more of a judgment call as to what your realistic baseline is (what holds your weight steady), and the decisions you make on how many additional calories and what macros are needed to progress. Make the changes, see how far you get, make more changes, etc. Ultimately, they will require more calories over time and WIND UP pushing food. THAT'S what we should be recognizing.
So the entire conversation and its context rests upon how well you make decisions. It's not about hardcore eating or shoveling food down. It's about your overall strategy, the week to week/month to month decisions.
So yeah, if your baseline calorie needs are 3000, and you spend your off-season eating 3300-3400 calories, you're not going to grow muscle. But if you turn 3400 into 3600, 3600 into 3800, 3800 into 4000 (and beyond)... all while trying to stay on the leaner side (never losing sight of your abs), you'll absolutely start growing accordingly... and you won't have to spend the first 6-8 weeks of a dieting phase cleaning up a mess.
I made the mistake of pushing food too far back in the DC Training days. I got strong and I got fat. At 40 going on 41, with a more calculated approach, I can still gain muscle at a similar rate. It's not genetics. It's not more drugs. It's just accounting for everything at all times.