Do you have source for this? Because as you write I've always read to derive protein intake from the overall weight. That would indeed be a very important distance.
> Protein intake should range between 1.0-1.5 grams/kg of adjusted body weight. To calculate adjusted body weight, first calculate excess weight: Excess weight = current weight — ideal body weight (IBW). Adjusted body weight = IBW + 0.25 of excess body weight. This amount generally accounts for 20% to 30% of total caloric intake.
So a slightly more complex way of calculating roughly the same thing. I'd argue that for most people getting your ideal weight is a good enough approximation, and that using your overweight/obese body fat in your protein calculation is wrong by a lot no matter which calculation you use.
https://www.ajmc.com/view/chapter-2-clinical-nutrition-guide...