Protein Intake Greater than the RDA Differentially Influences Whole-Body Lean Mass Responses to Purposeful Catabolic and Anabolic Stressors: A Systematic Review and Meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 31794597 · doi:10.1093/advances/nmz106
What was done
Authors conducted a systematic review and meta-analysis of randomized, controlled, parallel-group trials lasting at least 6 weeks in apparently healthy adults (aged ≥19 years). They evaluated whether protein intake greater than the Recommended Dietary Allowance (RDA of 0.8 g · kg⁻¹ · d⁻¹) compared to consuming the RDA differentially affected changes in whole-body lean mass across catabolic (energy restriction), anabolic (resistance training), and non-stressed conditions. Databases (PubMed, Scopus, CINAHL, Cochrane) were searched through August 2018. Eighteen studies yielding 22 comparisons met inclusion criteria.
What was found
Across all 22 comparisons, protein intake greater than the RDA significantly improved lean mass changes compared to the RDA (weighted mean difference [WMD]: 0.32 kg; 95% CI: 0.01, 0.64 kg). Subgroup analyses revealed: - Energy restriction (ER): Higher protein attenuated lean mass loss (WMD: 0.36 kg; 95% CI: 0.06, 0.67 kg; n = 14 comparisons). - Resistance training (RT): Higher protein increased lean mass gains (WMD: 0.77 kg; 95% CI: 0.23, 1.31 kg; n = 3 comparisons). - Non-stressed conditions (no ER and no RT): No significant difference in lean mass change (WMD: 0.08 kg; 95% CI: -0.59, 0.75 kg; n = 7 comparisons).
Why it matters
This review shows that while the current RDA of 0.8 g · kg⁻¹ · d⁻¹ is adequate to preserve lean mass in sedentary, weight-stable adults, higher protein intakes are necessary to preserve muscle tissue during calorie restriction or maximize muscle gains during resistance exercise.
Limits
The total number of participants is not reported in the abstract. Subgroup sample sizes were limited, particularly for resistance training without energy restriction (only 3 comparisons). The abstract does not specify the exact protein amounts consumed above the RDA, the duration of interventions beyond the 6-week minimum, or the specific methods used to measure lean mass.
Cited by
- supports The Recommended Dietary Allowance (RDA) for dietary protein is 0.8 grams per kilogram of body weight per day.