Why is the protein recommendation for strength building dependent on bodyweight?

Question

I've just started Starting Strength today and it's recommended to ensure protein intake is adequate to feed muscle growth so the next lift can be made at a heavier weight--the 1g protein per pound bodyweight being suggested.

I don't really see why it's dependent on the person's weight if both light guy and heavy guy still increase by the same amount amount each workout. Wouldn't the muscle growth for all required to lift another 5 pound be the same?

Answer 1

I have seen protein suggestions based on all kind of factors: body weight, lean body weight or lean body weight modified by muscle mass.

The only one of those you can discretely measure is body weight. Body fat measurements are not really accurate and as a result you'd get an inaccurate lean body weight number. Same goes for determining the muscle mass.
Then you have different sized people, people with longer or bigger muscles and people that have thinner or smaller ones.
How the protein metabolism works isn't completely understood, too.
And lastly not every protein source is as valuable as the other. What counts are the amino acids that make up the different types of protein. There are some high value and some lesser value proteins. But if you combine two lesser value protein sources they can get high value, just because the proportions of needed amino acids evened each other out.

So as you can see it would be really complex to put all those factors, which have high uncertainties, into a formula to calculate a specific result. It would be absolutely inaccurate anyway, it is far easier to give you a discrete number.

In fact the 2g/kg are the maximum that can effectively metabolized, everything above it isn't going to waste, but most certainly isn't used for muscle build up, but converted to energy.

So instead of recommending you something that might be insufficient, Starting Strength just goes with the maximum as their simple estimation.

Answer 2

People need protein for their current muscles as well as new muscle. From what I hear, people who are 280 pounds of muscle needs to do quite a bit of dedicated eating to stay at that weight.

For instance, see Alistair Overeem, heavyweight MMA fighter, describe how much he needs to eat in order to stay as big as he is (and to sustain his training schedule). Or read about the effort just to maintain a high bodyweight in Matt Reynold's article, Eating Through the Sticking Points.