I’m wondering if there is an equation for how much muscle mass would be gained from # minutes of exercise, per activity X. Or how many kg of fat would convert into muscle?
Of course it would vary by individual, but just like BMR is a very narrow age when the age, sex and height are given, so I would expect the muscle gain to be.
It’s way too variable. You could put 10 people on identical routines, identical nutrition, sleep, etc. and have vastly different outcomes.
Fat does not “convert” to muscle.
It may well be that under some combo of diet and exercise someone loses some fat and gains some muscle. But those are two unrelated *ab initio *processes.
If you want to get technical enough at the chemical level, you can say some hydrogen or carbon or whatever molecules that used to be in a fat cell are now in a muscle cell. But if you’re going to say that, you may as well say that your body converts cow muscle and fat cells into human skin and bone cells. It also converts plant leaves and roots into neurons and red blood cells. Which seems a pretty useless thing to believe. After all, most of those atoms came from galactic supernovas. Does your body convert supernovas to muscle?
Yes, but only in a way that makes a mockery of the word “convert”.
Lyle McDonald suggests the following relationship between years of proper training and expected muscle mass gains for natural bodybuilders here:
https://www.bodyrecomposition.com/muscle-gain/whats-my-genetic-muscular-potential.html/
To build muscle, you must exercise the muscle in specific ways. Some exercises will build little or no muscle no matter how long you do them. You can go jogging for hours and hours and gain little to no muscle (see marathon runners). Or you can do 3 minutes of very heavy squats and your muscles will get a little bit bigger.
To make the muscle larger, you need to exert your muscle so that the fibers experience microtears. Then your body repairs the muscle and makes it a little bigger. Then you again exert the muscle to create microtears, and your body again repairs, making it a bit bigger.
The way to do this is to exercise your muscle with a heavy weight with a certain amount of repetitions. If the weight is too light, you won’t get the micortears. If the weight is too heavy, you’ll tear the muscle and injure yourself.
Weightlifting is basically simple, but it’s more technical than other workouts. You need to understand how much weight to do, how many times to lift it, correct posture, etc. If you’re just starting out, try working with a trainer or experienced weightlifting friend so you can quickly get on the right track.
Fat will not ‘convert’ into muscle. Fat is burned for energy, and that energy can be used to lift weights or do other activities. You can calculate how much energy your body burns based on minutes of exercise. There are many places where you can enter your weight, activity, level of exertion, and duration and it will tell you how many calories are used. Those values are based on averages and won’t be exactly accurate for your particular body, but they’ll give you a good estimate.