How Do You Eat for Muscle Gains Without Getting Fat?
First, you have understand that the metabolism is not a great multitasker. It likes to be building up fat and muscle (anabolism) or tearing them both down (catabolism).
Trying to do both at once is the metabolic equivalent of patting your head and rubbing your belly. You can do it, it's just not that easy... unless you're a beginner or using anabolics.
The trick here is to understand you have four different metabolic toggles to pull:
1 Eat less, exercise more.
This will burn fat and muscle because it creates a pretty intense and wide calorie gap through both exercise and food. Think marathon runner or skinny fat.
2 Eat more, exercise less.
This will put on both muscle and fat through creating a calorie gap in the other direction. Think powerlifter or muscle-fat.
That latter scenario is what most people try to do when they want to gain muscle. It works, but it often makes you look like you just put a jacket on top of two sweaters. It's not the best approach or the best look. This is usually creating a 500-calorie surplus or more, and that may be too much if the training isn't right.
3 Eat less, exercise less.
Think the little old lady in Paris who climbs four flights of stairs six times a day, but eats only half a baguette, a cup each of coffee and wine, a radish, and some cheese. She stays lean because she drives the calorie deficit through diet and moves enough to not become a skeleton.
4 Eat more, exercise more.
That's the toggle you want. It's the athlete toggle. Ramp up your food intake to a slight surplus so you can gain some muscle. I suggest somewhere between 15 and 20 times body weight in pounds depending on whether or not you're a hard gainer. If you tend to get "muscle-fat" easily (like me), stay near 15 to start.
Now set your macronutrients to 40-30-30 (carbs, protein, and fat). You'll need the extra carbs. Insulin is, after all, the most powerful anabolic hormone in the body. If you can't get that fuel in the cell, you're not going to grow no matter how much testosterone you have.
Now turn on the training intensity like you're a banshee in a bench, squat, and deadlift competition to the death. Doing things this way will amplify energy flux, reduce fat (or at least minimize its accumulation) and put mechanical pressure on the muscle to grow.
If it's not working, SLOWLY ramp up the calories until it does. My guess is you'll end up in a slight surplus of 200-400 calories. This is the best way to multitask.