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.

Robert W Morton; Kevin T Murphy; Sean R McKellar; Brad J Schoenfeld; Menno Henselmans; Eric Helms; Alan A Aragon; Michaela C Devries; Laura Banfield; James W Krieger; Stuart M Phillips

British journal of sports medicine, 2018

SR / meta-analysisCC BY-NCCorrectedData current as of 25 Oct 2026

Non-commercial licence: shown because this platform is non-commercial.

Abstract

OBJECTIVE: We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength. DATA SOURCES: A systematic search of Medline, Embase, CINAHL and SportDiscus. ELIGIBILITY CRITERIA: Only randomised controlled trials with RET ≥6 weeks in duration and dietary protein supplementation. DESIGN: Random-effects meta-analyses and meta-regressions with four a priori determined covariates. Two-phase break point analysis was used to determine the relationship between total protein intake and changes in fat-free mass (FFM). RESULTS: Data from 49 studies with 1863 participants showed that dietary protein supplementation significantly (all p<0.05) increased changes (means (95% CI)) in: strength-one-repetition-maximum (2.49 kg (0.64, 4.33)), FFM (0.30 kg (0.09, 0.52)) and muscle size-muscle fibre cross-sectional area (CSA; 310 µm^2 (51, 570)) and mid-femur CSA (7.2 mm^2 (0.20, 14.30)) during periods of prolonged RET. The impact of protein supplementation on gains in FFM was reduced with increasing age (-0.01 kg (-0.02,-0.00), p=0.002) and was more effective in resistance-trained individuals (0.75 kg (0.09, 1.40), p=0.03). Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM. SUMMARY/CONCLUSION: Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults. Increasing age reduces and training experience increases the efficacy of protein supplementation during RET. With protein supplementation, protein intakes at amounts greater than ~1.6 g/kg/day do not further contribute RET-induced gains in FFM.

Source: PubMed. Shown under the article’s CC BY-NC licence.

Where this study is used

Higher vs lower daily protein intake during resistance training: Fat mass (Adults with resistance training) — High. Counted in the grade.
Higher vs lower daily protein intake during resistance training: Maximal strength (1RM) (Adults with resistance training) — High. Counted in the grade.
Higher vs lower daily protein intake during resistance training: Muscle fibre cross-sectional area (Adults with resistance training) — Moderate. Counted in the grade.
Higher vs lower daily protein intake during resistance training: Muscle hypertrophy (direct imaging) (Adults with resistance training) — Moderate. Counted in the grade.

Extracted values

AI-assisted extraction: each number comes with the sentence it was read from.

Studies pooled: 49
Participants pooled: 1863
Funding: SMP thanks the Canada Research Chairs, Canadian Institutes for Health Research, and the Natural Science and Engineering Research Council of Canada for their support during the completion of this work.

Study-level values with their source sentences
Field	Value	Source sentence
Review question	We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength.	Show quote for Review question We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength. Located at `sec:abstract.1/p:0`
Population	healthy adults	Show quote for Population healthy adults Located at `title`
Intervention · Agent	dietary protein supplementation

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.

Robert W Morton; Kevin T Murphy; Sean R McKellar; Brad J Schoenfeld; Menno Henselmans; Eric Helms; Alan A Aragon; Michaela C Devries; Laura Banfield; James W Krieger; Stuart M Phillips

British journal of sports medicine, 2018

SR / meta-analysisCC BY-NCCorrectedData current as of 25 Oct 2026

Non-commercial licence: shown because this platform is non-commercial.

Abstract

Source: PubMed. Shown under the article’s CC BY-NC licence.

Extracted values

AI-assisted extraction: each number comes with the sentence it was read from.

Studies pooled: 49
Participants pooled: 1863
Funding: SMP thanks the Canada Research Chairs, Canadian Institutes for Health Research, and the Natural Science and Engineering Research Council of Canada for their support during the completion of this work.

Study-level values with their source sentences
Field	Value	Source sentence
Review question	We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength.	Show quote for Review question We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength. Located at `sec:abstract.1/p:0`
Population	healthy adults	Show quote for Population healthy adults Located at `title`
Intervention · Agent	dietary protein supplementation

Field	Value	Source sentence
Outcome name	1RM	Show quote for Outcome name 1RM (kg) Located at `table:T1/r:0/c:2`
Effect measure	MD	Show quote for Effect measure mean difference (MD) Located at `sec:2.5/p:0`
Point estimate	2.49	Show quote for Point estimate 2.49 (0.64 to 4.33) Located at `table:T1/r:2/c:2`
Ci low	0.64	Show quote for Ci low 2.49 (0.64 to 4.33) Located at `table:T1/r:2/c:2`
Ci high	4.33	Show quote for Ci high 2.49 (0.64 to 4.33) Located at `table:T1/r:2/c:2`
Ci level	95	Show quote for Ci level 95% CIs Located at `sec:2.5/p:0`
Unit	kg	Show quote for Unit 1RM (kg) Located at `table:T1/r:0/c:2`
P value	0.01	Show quote for P value 0.01 Located at `table:T1/r:2/c:6`
I2	33	Show quote for I2 33% Located at `table:T1/r:2/c:5`
Tau2	6.05	Show quote for Tau2 6.05 Located at `table:T1/r:2/c:3`
Pooling model	random	Show quote for Pooling model Random-effects meta-analyses were performed in RevMan Located at `sec:2.5/p:0`
N studies	28	Show quote for N studies 28 Located at `table:T1/r:2/c:1`
Analysis kind	primary	Show quote for Analysis kind Protein supplementation during prolonged RET significantly improved gains in 1RM strength (MD: 2.49 kg (0.64, 4.33), p=0.01; figure 2) Located at `sec:3.6/p:0`

Field	Value	Source sentence
Outcome name	MVC	Show quote for Outcome name had no effect on MVC Located at `sec:3.6/p:0`
Effect measure	SMD	Show quote for Effect measure SMD: 0.04 (-0.09, 0.16), p=0.54 Located at `sec:3.6/p:0`
Effect measure as written	SMD	Show quote for Effect measure as written SMD: 0.04 (-0.09, 0.16), p=0.54 Located at `sec:3.6/p:0`
Point estimate	0.04	Show quote for Point estimate SMD: 0.04 (-0.09, 0.16), p=0.54 Located at `sec:3.6/p:0`
Ci low	−0.09	Show quote for Ci low SMD: 0.04 (-0.09, 0.16), p=0.54 Located at `sec:3.6/p:0`
Ci high	0.16	Show quote for Ci high SMD: 0.04 (-0.09, 0.16), p=0.54 Located at `sec:3.6/p:0`
Ci level	95	Show quote for Ci level 95% CIs Located at `sec:2.5/p:0`
P value	0.54	Show quote for P value p=0.54 Located at `sec:3.6/p:0`
Pooling model	random	Show quote for Pooling model Random-effects meta-analyses were performed in RevMan Located at `sec:2.5/p:0`
Analysis kind	primary	Show quote for Analysis kind Protein supplementation during prolonged RET significantly improved gains in 1RM strength Located at `sec:3.6/p:0`

Field	Value	Source sentence
Outcome name	TBM	Show quote for Outcome name changes in TBM Located at `sec:3.6/p:0`
Effect measure	MD	Show quote for Effect measure MD: 0.11 kg (−0.23, 0.46), p=0.52 Located at `sec:3.6/p:0`
Effect measure as written	MD	Show quote for Effect measure as written MD: 0.11 kg (−0.23, 0.46), p=0.52 Located at `sec:3.6/p:0`
Point estimate	0.11	Show quote for Point estimate MD: 0.11 kg (−0.23, 0.46), p=0.52 Located at `sec:3.6/p:0`
Ci low	−0.23	Show quote for Ci low MD: 0.11 kg (−0.23, 0.46), p=0.52 Located at `sec:3.6/p:0`
Ci high	0.46	Show quote for Ci high MD: 0.11 kg (−0.23, 0.46), p=0.52 Located at `sec:3.6/p:0`
Ci level	95	Show quote for Ci level 95% CIs Located at `sec:2.5/p:0`
Unit	kg	Show quote for Unit MD: 0.11 kg Located at `sec:3.6/p:0`
P value	0.52	Show quote for P value p=0.52 Located at `sec:3.6/p:0`
Pooling model	random	Show quote for Pooling model Random-effects meta-analyses were performed in RevMan Located at `sec:2.5/p:0`
Analysis kind	primary	Show quote for Analysis kind Protein supplementation did not have a significant effect on changes in TBM Located at `sec:3.6/p:0`

Field	Value	Source sentence
Outcome name	Fat-free mass	Show quote for Outcome name Fat-free mass (kg) Located at `table:T1/r:0/c:7`
Effect measure	MD	Show quote for Effect measure mean difference (MD) Located at `sec:2.5/p:0`
Point estimate	0.3	Show quote for Point estimate 0.30 (0.09 to 0.52) Located at `table:T1/r:2/c:8`
Ci low	0.09	Show quote for Ci low 0.30 (0.09 to 0.52) Located at `table:T1/r:2/c:8`
Ci high	0.52	Show quote for Ci high 0.30 (0.09 to 0.52) Located at `table:T1/r:2/c:8`
Ci level	95	Show quote for Ci level 95% CIs Located at `sec:2.5/p:0`
Unit	kg	Show quote for Unit Fat-free mass (kg) Located at `table:T1/r:0/c:7`
P value	0.007	Show quote for P value p=0.007 Located at `sec:3.6/p:0`
I2	7	Show quote for I2 7% Located at `table:T1/r:2/c:11`
Tau2	0.05	Show quote for Tau2 0.05 Located at `table:T1/r:2/c:9`
Pooling model	random	Show quote for Pooling model Random-effects meta-analyses were performed in RevMan Located at `sec:2.5/p:0`
N studies	27	Show quote for N studies 27 Located at `table:T1/r:2/c:7`
Analysis kind	primary	Show quote for Analysis kind improved changes in FFM (MD: 0.30 kg (0.09, 0.52), p=0.007; figure 3) Located at `sec:3.6/p:0`

Field	Value	Source sentence
Outcome name	FM	Show quote for Outcome name FM (MD: −0.41 kg (−0.70,–0.13), p=0.005) Located at `sec:3.6/p:0`
Effect measure	MD	Show quote for Effect measure MD: −0.41 kg (−0.70,–0.13), p=0.005 Located at `sec:3.6/p:0`
Effect measure as written	MD	Show quote for Effect measure as written MD: −0.41 kg (−0.70,–0.13), p=0.005 Located at `sec:3.6/p:0`
Point estimate	−0.41	Show quote for Point estimate MD: −0.41 kg (−0.70,–0.13), p=0.005 Located at `sec:3.6/p:0`
Ci low	−0.7	Show quote for Ci low MD: −0.41 kg (−0.70,–0.13), p=0.005 Located at `sec:3.6/p:0`
Ci high	−0.13	Show quote for Ci high MD: −0.41 kg (−0.70,–0.13), p=0.005 Located at `sec:3.6/p:0`
Ci level	95	Show quote for Ci level 95% CIs Located at `sec:2.5/p:0`
Unit	kg	Show quote for Unit MD: −0.41 kg Located at `sec:3.6/p:0`
P value	0.005	Show quote for P value p=0.005 Located at `sec:3.6/p:0`
Pooling model	random	Show quote for Pooling model Random-effects meta-analyses were performed in RevMan Located at `sec:2.5/p:0`
Analysis kind	primary	Show quote for Analysis kind improved changes in FFM (MD: 0.30 kg (0.09, 0.52), p=0.007; figure 3), FM (MD: −0.41 kg (−0.70,–0.13), p=0.005), fibre CSA (MD: 310 µm^2 (51, 570), p=0.02; see online supplementary figure 2: panel A) and mid-femur CSA (MD: 7.2 mm^2 (0.20, 14.30), p=0.04; see online supplementary figure 2: panel B) during prolonged RET. Located at `sec:3.6/p:0`

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.

Abstract

Where this study is used

Extracted values

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.

Abstract

Where this study is used

Extracted values

1RM

MVC

TBM

Fat-free mass

FM

fibre CSA

mid-femur CSA

one-repetition-maximum · untrained

one-repetition-maximum · trained

lean or fat-free mass · untrained

lean or fat-free mass · trained

FFM · old

FFM · young

fibre CSA · Mitchell et al ^50 was included in the fibre CSA assessment

FFM

1RM · Baseline protein intake

1RM · Age

1RM · Training status

Fat-free mass · Baseline protein intake

Fat-free mass · Protein dose

Fat-free mass · Age

Fat-free mass · Training status

How these values were extracted

Field	Value	Source sentence
Outcome name	fibre CSA	Show quote for Outcome name fibre CSA (MD: 310 µm^2 (51, 570), p=0.02 Located at `sec:3.6/p:0`
Effect measure	MD	Show quote for Effect measure MD: 310 µm^2 (51, 570), p=0.02 Located at `sec:3.6/p:0`
Effect measure as written	MD	Show quote for Effect measure as written MD: 310 µm^2 (51, 570), p=0.02 Located at `sec:3.6/p:0`
Point estimate	310	Show quote for Point estimate MD: 310 µm^2 (51, 570), p=0.02 Located at `sec:3.6/p:0`
Ci low	51	Show quote for Ci low MD: 310 µm^2 (51, 570), p=0.02 Located at `sec:3.6/p:0`
Ci high	570	Show quote for Ci high MD: 310 µm^2 (51, 570), p=0.02 Located at `sec:3.6/p:0`
Ci level	95	Show quote for Ci level 95% CIs Located at `sec:2.5/p:0`
Unit	µm^2	Show quote for Unit MD: 310 µm^2 (51, 570) Located at `sec:3.6/p:0`
P value	0.02	Show quote for P value p=0.02 Located at `sec:3.6/p:0`
Pooling model	random	Show quote for Pooling model Random-effects meta-analyses were performed in RevMan Located at `sec:2.5/p:0`
Analysis kind	primary	Show quote for Analysis kind improved changes in FFM (MD: 0.30 kg (0.09, 0.52), p=0.007; figure 3), FM (MD: −0.41 kg (−0.70,–0.13), p=0.005), fibre CSA (MD: 310 µm^2 (51, 570), p=0.02; see online supplementary figure 2: panel A) and mid-femur CSA (MD: 7.2 mm^2 (0.20, 14.30), p=0.04; see online supplementary figure 2: panel B) during prolonged RET. Located at `sec:3.6/p:0`

Field	Value	Source sentence
Outcome name	mid-femur CSA	Show quote for Outcome name mid-femur CSA (MD: 7.2 mm^2 (0.20, 14.30), p=0.04 Located at `sec:3.6/p:0`
Effect measure	MD	Show quote for Effect measure MD: 7.2 mm^2 (0.20, 14.30), p=0.04 Located at `sec:3.6/p:0`
Effect measure as written	MD	Show quote for Effect measure as written MD: 7.2 mm^2 (0.20, 14.30), p=0.04 Located at `sec:3.6/p:0`
Point estimate	7.2	Show quote for Point estimate MD: 7.2 mm^2 (0.20, 14.30), p=0.04 Located at `sec:3.6/p:0`
Ci low	0.2	Show quote for Ci low MD: 7.2 mm^2 (0.20, 14.30), p=0.04 Located at `sec:3.6/p:0`
Ci high	14.3	Show quote for Ci high MD: 7.2 mm^2 (0.20, 14.30), p=0.04 Located at `sec:3.6/p:0`
Ci level	95	Show quote for Ci level 95% CIs Located at `sec:2.5/p:0`
Unit	mm^2	Show quote for Unit MD: 7.2 mm^2 (0.20, 14.30) Located at `sec:3.6/p:0`
P value	0.04	Show quote for P value p=0.04 Located at `sec:3.6/p:0`
Pooling model	random	Show quote for Pooling model Random-effects meta-analyses were performed in RevMan Located at `sec:2.5/p:0`
Analysis kind	primary	Show quote for Analysis kind improved changes in FFM (MD: 0.30 kg (0.09, 0.52), p=0.007; figure 3), FM (MD: −0.41 kg (−0.70,–0.13), p=0.005), fibre CSA (MD: 310 µm^2 (51, 570), p=0.02; see online supplementary figure 2: panel A) and mid-femur CSA (MD: 7.2 mm^2 (0.20, 14.30), p=0.04; see online supplementary figure 2: panel B) during prolonged RET. Located at `sec:3.6/p:0`

Field	Value	Source sentence
Outcome name	one-repetition-maximum	Show quote for Outcome name shown as mean difference with 95% CIs on one-repetition-maximum (1 RM; kg) Located at `fig:F2/caption`
Effect measure	MD	Show quote for Effect measure shown as mean difference with 95% CIs Located at `fig:F2/caption`
Point estimate	0.99	Show quote for Point estimate untrained: 0.99 kg (−0.27, 2.25), p=0.12 Located at `fig:F2/caption`
Ci low	−0.27	Show quote for Ci low untrained: 0.99 kg (−0.27, 2.25), p=0.12 Located at `fig:F2/caption`
Ci high	2.25	Show quote for Ci high untrained: 0.99 kg (−0.27, 2.25), p=0.12 Located at `fig:F2/caption`
Ci level	95	Show quote for Ci level shown as mean difference with 95% CIs Located at `fig:F2/caption`
Unit	kg	Show quote for Unit untrained: 0.99 kg Located at `fig:F2/caption`
P value	0.12	Show quote for P value p=0.12 Located at `fig:F2/caption`
Pooling model	random	Show quote for Pooling model Forest plot of the results from a random-effects meta-analysis Located at `fig:F2/caption`
Subgroup	untrained	Show quote for Subgroup The rhombi represent the weighted untrained, trained and total group’s mean difference. Located at `fig:F2/caption`
Analysis kind	subgroup	Show quote for Analysis kind in untrained and trained participants Located at `fig:F2/caption`

Field	Value	Source sentence
Outcome name	lean or fat-free mass	Show quote for Outcome name on lean or fat-free mass (FFM; kg) Located at `fig:F3/caption`
Effect measure	MD	Show quote for Effect measure shown as mean difference with 95% CIs Located at `fig:F3/caption`
Effect measure as written	mean difference	Show quote for Effect measure as written mean difference Located at `fig:F3/caption`
Point estimate	0.15	Show quote for Point estimate untrained: 0.15 kg (−0.02, 0.31), p=0.08 Located at `fig:F3/caption`
Ci low	−0.02	Show quote for Ci low untrained: 0.15 kg (−0.02, 0.31), p=0.08 Located at `fig:F3/caption`
Ci high	0.31	Show quote for Ci high untrained: 0.15 kg (−0.02, 0.31), p=0.08 Located at `fig:F3/caption`
Ci level	95	Show quote for Ci level shown as mean difference with 95% CIs Located at `fig:F3/caption`
Unit	kg	Show quote for Unit untrained: 0.15 kg Located at `fig:F3/caption`
P value	0.08	Show quote for P value p=0.08 Located at `fig:F3/caption`
Pooling model	random	Show quote for Pooling model Forest plot of the results from a random-effects meta-analysis Located at `fig:F3/caption`
Subgroup	untrained	Show quote for Subgroup The rhombi represent the weighted untrained, trained and total group’s mean difference. Located at `fig:F3/caption`
Analysis kind	subgroup	Show quote for Analysis kind in untrained and trained participants Located at `fig:F3/caption`

Field	Value	Source sentence
Outcome name	FFM	Show quote for Outcome name changes in FFM Located at `sec:3.7/p:1`
Effect measure	MD	Show quote for Effect measure MD: 0.06 (-0.14, 0.26) Located at `sec:3.7/p:1`
Effect measure as written	MD	Show quote for Effect measure as written MD: 0.06 (-0.14, 0.26) Located at `sec:3.7/p:1`
Point estimate	0.06	Show quote for Point estimate MD: 0.06 (-0.14, 0.26) Located at `sec:3.7/p:1`
Ci low	−0.14	Show quote for Ci low MD: 0.06 (-0.14, 0.26) Located at `sec:3.7/p:1`
Ci high	0.26	Show quote for Ci high MD: 0.06 (-0.14, 0.26) Located at `sec:3.7/p:1`
Subgroup	old	Show quote for Subgroup old (>45; 67±7 years; MD: 0.06 (-0.14, 0.26)) Located at `sec:3.7/p:1`
Analysis kind	subgroup	Show quote for Analysis kind When the effect of protein supplementation on changes in FFM was evaluated with age stratified into two subgroups Located at `sec:3.7/p:1`

Field	Value	Source sentence
Outcome name	fibre CSA	Show quote for Outcome name fibre CSA assessment Located at `sec:3.5/p:0`
Point estimate	153	Show quote for Point estimate 153 µm^2 (−137, 443), p=0.30 Located at `sec:3.5/p:0`
Ci low	−137	Show quote for Ci low 153 µm^2 (−137, 443), p=0.30 Located at `sec:3.5/p:0`
Ci high	443	Show quote for Ci high 153 µm^2 (−137, 443), p=0.30 Located at `sec:3.5/p:0`
Unit	µm^2	Show quote for Unit 153 µm^2 (−137, 443) Located at `sec:3.5/p:0`
P value	0.3	Show quote for P value p=0.30 Located at `sec:3.5/p:0`
Subgroup	Mitchell et al ^50 was included in the fibre CSA assessment	Show quote for Subgroup when Mitchell et al ^50 was included in the fibre CSA assessment Located at `sec:3.5/p:0`
Analysis kind	sensitivity	Show quote for Analysis kind Sensitivity analysis was performed with the nine high-risk studies mentioned above included Located at `sec:3.5/p:0`

Field	Value	Source sentence
Outcome name	FFM	Show quote for Outcome name the change in FFM and daily protein intake Located at `sec:3.8/p:0`
Effect measure	other	Show quote for Effect measure break point=1.62 (1.03, 2.20) g/kg/day Located at `sec:3.8/p:0`
Point estimate	1.62	Show quote for Point estimate break point=1.62 (1.03, 2.20) g/kg/day Located at `sec:3.8/p:0`
Ci low	1.03	Show quote for Ci low break point=1.62 (1.03, 2.20) g/kg/day Located at `sec:3.8/p:0`
Ci high	2.2	Show quote for Ci high break point=1.62 (1.03, 2.20) g/kg/day Located at `sec:3.8/p:0`
Ci level	95	Show quote for Ci level (95% CI: 1.03 to 2.20) Located at `sec:4.2/p:4`
Unit	g/kg/day	Show quote for Unit break point=1.62 (1.03, 2.20) g/kg/day Located at `sec:3.8/p:0`
P value	0.079	Show quote for P value p=0.079 Located at `sec:3.8/p:0`
N participants	723	Show quote for N participants 723 participants Located at `sec:3.8/p:0`
Analysis kind	dose_response	Show quote for Analysis kind Biphasic regression (42 study arms, 723 participants) explained more variation than a linear regression Located at `sec:3.8/p:0`