As a personal trainer, what would you advise in terms of getting sufficient protein and calories to build mass - if I had to limit the (physical) amount of food I can eat as much as possible?
I'm not a personal trainer but I've built mass and been on many a diet before (like right now actually
) and watched dozens upon dozens of YT clips including those of personal trainers and pro bb'ers so here's my "bro science" take.
For starters, an important thing to keep in mind is this rule of thumb:
1g protein = about 4kcal
1g carbs = about 4kcal
1g fat = 9kcal
So as we can see, protein and carbs have the same multiplier while fat has a MUCH higher multiplier.
If you want to build mass and not get unreasonably fat in the process then you should eat about 2g of protein per kg of body weight. For me, at 80kg body weight, I'd try to hit ~160g protein/day which would put my protein-based calorie intake at around 640kcal (x 4 multiplier).
Carbs and fat distribution don't really matter very much when you are trying to build muscle. Don't go overboard with fat though. 1g to 1.5g per kg body weight should do. Fill up the rest with carbs to have enough energy for your heavy workouts.
When you are trying to lose weight, however, then -obviously- you should reduce fat because of its high x9 multiplier so if you want to maintain muscle mass in a diet as much as possible, you should eat the same 2g of protein per kg body weight, reduce fat to about 0.5g of fat per kg body weight and fill up the rest with carbs up to your daily max calories.
Finally, as for the daily max calories, whether it is in your bulk or your lean phase, you just have to experiment because no two bodies are the same. Your daily activity level matters, your specific metabolism matters, your workout routine matters, there is no one-size-fits-all solution.
So you just have to experiment, e.g. when bulking and trying to put on "lean" mass, you could start with taking in anywhere between 3000 and 4000kcal per day and watch what happens. Do you put on weight, do you gain muscle and strength, do you gain muscle but also too much fat at the same time? Then adjust your calorie intake accordingly.
Same with a diet. You could start with a moderate deficit and e.g. eat 2000kcal/day. Then check after a week. Did you lose a reasonable amount of weight (~1kg = reasonable)? If yes, keep at it. If no, increase the deficit moderately and try maybe 1800kcal as a next step.
If you lost an unreasonable amount of weight, like 2kg+ in a week then increase your calorie intake to protect your muscle mass better.
In a nutshell: Check. Adjust. Check. Adjust. Check. Adjust. Or don't adjust but just keep at it if it works, of course. Be patient and don't cheat. That is all there is to it. It is really simple actually. You just have to do it is all
.
