Meta-analysis — 2018 — Protein & nutrition · Hypertrophy · Strength · Body composition
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults
What did the researchers investigate?
Whether protein supplementation adds to gains in muscle mass and strength from resistance training, across 49 randomised trials with 1,863 participants.
What did they find?
Protein supplementation significantly increased gains in 1RM strength, fat-free mass and muscle size. The effect fell with age and was greater in trained people. Total protein intakes above about 1.62 g/kg/day gave no further gains in fat-free mass.
What does this mean for training?
Enough daily protein supports training results; there is a point beyond which more adds little for muscle mass.
How does FitX AI use this evidence?
FitX AI's daily protein target is 1.6-2.2 g per kg of body weight (1.8 by default): at or above the intake beyond which this analysis found no further gain in fat-free mass on average.
Where FitX AI's own choices go beyond this paper
Protein, carbohydrate, fat and fibre targets. Fat at 25% of calories with a 0.6 g/kg floor (Standard), the other diet types' carbs-to-fat splits of the calories after protein (High carb 50:20, Moderate carb 35:35, Zone 40:30, Low carb 20:40, Custom 5-95% carbohydrate), Ketogenic's carbohydrate at 5% of calories (at most 50 g), and fibre at 14 g per 1,000 kcal (a general dietary guideline, not in the library) are FitX AI choices. No diet type is presented as better for results: none is compared in the library.
Limitations
Supplementation trials varied in dose, timing and population; the break point is an average, not an individual requirement.