Will slight reductions in protein intake hurt your gains?
This recent study sought to determine the impact of an acute reduction in dietary protein intake on post-exercise anabolism in habitual consumers of high-protein diets.
In this crossover study, 5 resistance-trained men with a habitual protein intake of 1.9 – 3.0 g/kg/day consumed a moderate protein diet (MP; 1.2 g/kg/day) and a high protein diet (HP; 2.2 g/kg/day) with a one week washout period in-between. The MP condition began with 2 days of consuming 2.2 g/kg/day, then dropping to 1.2 g/kg/day for 5 days. The HP condition was only 2 days of consuming 2.2 g/kg/day; since it wasn’t a substantial deviation from their typical protein intake, a prolonged adaptation period wasn’t required. Resistance training occurred every other day throughout the interventions.
Whole-body net protein balance was significantly decreased on day 1 after switching from HP to the MP condition. Net protein balance began returning toward HP levels by day 3, and was reasonably close to full restoration by day 5. These results suggest that acute reductions in daily protein intake could transiently attenuate anabolic processes during recovery from exercise, but we can probably adapt to this drop within a week or so.
The bottom line: For most lifters aiming to maximize muscle mass, evidence suggests that daily protein intake should generally be around 1.6-2.2 g/kg/day. However, many lifters consistently eat more than this; since they’re habituated to very high daily protein intakes, they often wonder if dropping back down to this recommended range will lead to muscle loss. These data suggest that a transient drop in anabolism might be observed, but the lifter will most likely adapt to their new protein intake within a week or so, well before any measurable strength or muscle losses are likely to occur.