I have seen in a number of places that in order to maintain muscle mass you should eat something like 0.8-1g of protein per pound per day. Like the person in this question, I'm finding that I really have to focus on protein in order to get 160-180g of protein every day - for a 2500 calorie diet, since it's easy for carbs to take up a lot of calories and providing very little in the way of protein (this is not terribly difficult to do, mind you — two scoops of protein powder and a 16 oz container of low-fat cottage cheese gets me 92g of protein in 560 calories, so I just need to average 18% protein for the remaining 2000 calories, I just need to make sure to eat that or some equivalent every day).
However, I noticed the other day that for a 2000 calorie diet the FDA only recommends 50 g of protein! This seems like a huge gap, considering that very few people eating a 2000 calorie diet would weigh only 100 pounds. Is the 0.8-1g/lb recommendation only for people specifically doing weight training? Does the FDA dramatically underestimate the amount of protein people need? Is there some non-linearity here where your muscle mass won't fall below a certain threshold even if you have quite low protein intake?
I'll note that I found this page which seems to point towards a saturation effect where 0.8g/lb is the maximum amount of protein that has any effect on muscle synthesis¹:
I am not quite sure how to interpret this chart, however, since it seems to be gross muscle synthetic rate, not net (though I would guess based on the chart for "sedentary individual" that the baseline muscle protein loss is 20?).
- Chart from Lemon, P. W., Tarnopolsky, M. A., MacDougall, J. D., & Atkinson, S. A. (1992). Protein requirements and muscle mass/strength changes during intensive training in novice bodybuilders. Journal of applied physiology, 73(2), 767–775. https://doi.org/10.1152/jappl.19220.127.116.117