Deep Dive: Elevated protein intake can benefit lean mass

The current recommended dietary allowance (RDA) for protein was established in the early 2000s^[1]. It’s the relative (grams per kilogram of bodyweight per day) amount necessary for the maintenance of good health in otherwise healthy people. The RDA was created to guide people on how to avoid a progressive loss of lean body mass from inadequate protein intake.

In the time since the recommendations were published, a lot of research has been done on protein intake, leading to debate about whether the current RDA of 0.8 grams per kilogram of bodyweight per day is too low. Questions have also been raised concerning whether the RDA is appropriate for people who are dieting or resistance training. Adequate protein intake is important during energy restriction because losses in lean mass account for 20-30% of total weight loss^[2] in the absence of exercise. Higher protein intake also tends to improve lean mass and strength gains with resistance training^[3]. Other arguments for a higher protein intake include its promotion of muscle protein anabolism^[4], its thermic effect^[5], and its satiation^[6] effect compared to other macronutrients.

The RDA is supported by a meta-analysis^[7] of studies with nitrogen balance measurements. However, there are some issues with the use of nitrogen balance to determine protein intake, including loss of food while eating, loss of nitrogen in feces or urine, and potential losses through the skin^[8]. These errors tend to overestimate intake and underestimate output, which could lead to incorrect positive balances that translate to a lower estimated protein requirement. Furthermore, nitrogen balance studies are generally less than 30 days in duration, and don’t directly measure what most people actually care about: lean mass.