Study analysis · Physiological Reports · 2024
Chicken + resistance training gave older women the biggest muscle gains—but their gut bacteria barely noticed.
In older women, doing leg exercises and eating chicken three times a week for 12 weeks improved strength and lean mass more than either alone, without major changes to gut bacteria.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This is a randomized controlled trial, which is like a fair test where people were put into groups by chance. It can show that resistance training and eating chicken can cause improvements in muscle strength and mass, but because it's a single small study, we can't be 100% sure it works for everyone.
What’s the bottom line?
Scientists studied 93 older women. Some did leg exercises, some ate chicken, some did both, and some did neither. They checked muscle strength, muscle mass, and gut bacteria.
How strong is this study?
The study was well-designed with random groups and blinded assessors, but it was small and people knew if they were exercising or eating chicken, which could affect some results. Also, some groups started with different muscle mass, so we should be cautious about how much we trust the findings.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
77 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=93)+7.4/20
- Follow-up+10/10
100 / 100
46 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 566 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Randomization allows causal inference for the effects of resistance training and/or chicken meat on muscle strength and mass. However, small sample size per group, single-blind design (participants not blinded), baseline differences in lean body mass between some groups, short 12-week duration, and multiple comparisons limit the strength of causal conclusions. Causation cannot be established for the gut microbiome mechanism because no significant microbiota changes were observed and only a weak correlation was found.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding disclosures are present in the provided text, and the excerpt appears truncated, so COI/funding status cannot be fully determined.
Independent Analysis Safeguards
- Assessors blinded to group allocation
- Randomized controlled trial design
The provided text does not include a conflict of interest or funding statement; it appears truncated before acknowledgments. No industry funding or author COI can be confirmed or ruled out. The chicken meat intervention could imply possible industry involvement, but no provider or funder is disclosed.
Key takeaways
- 01
After 12 weeks: leg training alone made muscles stronger; chicken alone increased whole-body lean mass; doing both gave the biggest increases in strength and lean mass.
- 02
Gut bacteria overall did not change much.
- 03
One gut bacteria group went down and leg lean mass went up, but the link was weak (r = −0.323).
- 04
Exact muscle changes in kilograms or percent were not reported.
- 05
This is not a disease-risk study, so there is no absolute risk increase to report.
- 06
The abstract does not give exact kilograms or percent changes for muscle outcomes.
- 07
For a person, it suggests adding chicken and resistance training may help maintain muscle, but the exact amount of benefit is not known from this summary.
- 08
Gut bacteria changes were not significant after correction, so no clear harm or benefit there.
Surprising findings
- Gut microbiota composition did not change significantly after 12 weeks of resistance training and/or chicken meat intake, even after FDR correction.Previous animal and human studies suggested exercise and meat intake can alter gut bacteria. This trial found no significant overall or individual taxa changes.
- Chicken meat intake alone increased whole-body lean mass without any resistance training.Many guidelines emphasize that protein needs to be paired with resistance exercise to build muscle. Here, chicken alone produced a significant increase in whole-body lean mass compared with placebo.
- A decrease in the Eubacterium hallii group was weakly correlated with an increase in lower-limb lean mass.Eubacterium hallii is often considered a beneficial gut bacterium. A decrease being linked to muscle gain is counterintuitive, though the correlation is weak and not FDR-significant.
Practical takeaways
For older women, combining resistance training (3 days/week, leg exercises) with chicken meat (110 g, ~22.5 g protein, 3 days/week) may produce greater gains in strength and lean mass than either alone.
The study was small (18–22 per group after dropout), lasted only 12 weeks, and included healthy Japanese women aged 59–79. Exact gains were not reported.
medium confidenceDon't expect a 12-week resistance training or chicken intervention to dramatically change your gut microbiome.
Microbiome was measured with 16S rRNA sequencing, which has limited resolution. Longer or different interventions might still alter gut bacteria.
medium confidenceIf you can't start resistance training yet, adding a protein-rich food like chicken may still help support lean mass.
Chicken alone did not significantly improve strength in this study, and the lean mass benefit was seen over only 12 weeks in a specific population.
low confidenceFocus on strength and function, not just scale weight or muscle size, when evaluating progress.
This study measured maximal knee extension strength and DXA lean mass, not falls, fractures, or quality of life.
medium confidenceWhy this study matters
Combo beats solo for strength and lean mass
In a 12-week RCT of 93 older Japanese women (81 completed), the group doing resistance training plus chicken meat (RT+HP) had significantly greater increases in maximal muscle strength and whole-body lean mass than either the chicken-only (Sed+HP) or resistance-training-only (RT+PL) groups. However, exact absolute changes and effect sizes were not reported in the available text.
Many people wonder whether they need both exercise and extra protein to see real benefits. This study suggests the combination may outperform either alone for older women.
Chicken alone increased whole-body lean mass—without lifting
The sedentary group that ate 110 g of boiled chicken breast (22.5 g protein) three times per week for 12 weeks increased whole-body lean mass compared with the sedentary placebo group, even without resistance training. This was a significant between-group difference.
It suggests that simply adding a protein-rich food like chicken may help preserve or increase lean mass in older women, even before starting a workout program.
Resistance training alone made women stronger, not necessarily bigger
The resistance-training-only group (RT+PL) significantly increased maximal knee extension strength compared with sedentary groups, but lower-limb lean mass did not significantly increase compared with the sedentary placebo group. Only the combined group (RT+HP) showed a significant increase in lower-limb lean mass versus Sed+PL.
It highlights that strength gains and muscle size gains are not the same thing, especially over a short 12-week period.
Gut microbiome didn't budge
Gut microbiota beta-diversity and individual bacterial taxa did not change significantly before or after the intervention in any of the four groups. After false discovery rate (FDR) correction, no bacterial taxa showed significant alterations.
This contradicts the popular idea that exercise or eating meat quickly reshapes your gut bacteria. At least over 12 weeks in older women, the microbiome looked stable.
Weak link: Eubacterium hallii down, leg lean mass up
A decrease in the relative abundance of the Eubacterium hallii group was weakly negatively correlated with an increase in lower-limb lean mass (r = −0.323, p = 0.003). This correlation did not survive FDR correction for multiple comparisons.
It's counterintuitive: a decrease in a gut bacterium often considered beneficial was linked to muscle gain. But the link is weak and hypothesis-generating.
Small study, short duration, specific population
After dropout, per-group sample sizes were only 18–22 women. The intervention lasted 12 weeks, and participants were healthy Japanese women aged 59–79. Effect sizes, confidence intervals, and absolute changes were not reported in the abstract.
It's a useful reminder that promising headlines often come from small, short trials that need replication in broader groups.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists studied 93 older women. Some did leg exercises, some ate chicken, some did both, and some did neither. They checked muscle strength, muscle mass, and gut bacteria.
Research results
After 12 weeks: leg training alone made muscles stronger; chicken alone increased whole-body lean mass; doing both gave the biggest increases in strength and lean mass. Gut bacteria overall did not change much. One gut bacteria group went down and leg lean mass went up, but the link was weak (r = −0.323). Exact muscle changes in kilograms or percent were not reported.
What this means - more context
This is not a disease-risk study, so there is no absolute risk increase to report. The abstract does not give exact kilograms or percent changes for muscle outcomes. For a person, it suggests adding chicken and resistance training may help maintain muscle, but the exact amount of benefit is not known from this summary. Gut bacteria changes were not significant after correction, so no clear harm or benefit there.
Investigated whether 12 weeks of resistance training combined with chicken meat intake increases muscle mass and strength in older women and whether gut microbiota changes underlie the effect.
In a randomized controlled trial of 93 older women (59–79 years; 81 completed), resistance training alone increased maximal muscle strength, chicken meat intake alone increased whole-body lean mass, and the combination produced greater increases in maximal muscle strength and whole-body lean mass than either alone. Gut microbiota beta-diversity and individual taxa after FDR correction did not significantly change. A weak negative correlation was found between decrease in Eubacterium hallii group and increase in lower-limb lean mass (r = −0.323, p = 0.003). No relative risks or absolute risk outcomes were reported; muscle effect sizes and absolute changes were not specified in the available text.
Methods Used
Randomized controlled trial; 93 community-dwelling Japanese women aged 59–79 allocated to sedentary control + placebo (Sed+PL), sedentary + chicken meat (Sed+HP), resistance training + placebo (RT+PL), or resistance training + chicken meat (RT+HP). Resistance training: 3 days/week for 12 weeks, 3 sets of 10 leg extensions and leg curls at 70% 1RM. Chicken meat: 110 g boiled chicken breast containing 22.5 g protein, 3 days/week for 12 weeks; placebo was an energy-matched protein-free carbohydrate food. Outcomes included DXA body composition, maximal knee extension strength, and 16S rRNA fecal microbiota. Assessors were blinded to allocation.
Main Finding
Combining 12 weeks of high-intensity resistance training (3 days/week) with chicken meat intake (110 g containing 22.5 g protein, 3 days/week) probably produces greater increases in maximal muscle strength and whole-body lean mass than either intervention alone in older women aged 59–79. The study did not report relative risks or absolute risk; muscle effect sizes and absolute changes were not specified in the available abstract. Gut microbiota composition did not significantly change before or after intervention in any group, and no individual taxa survived FDR correction. A weak negative correlation was observed between change in Eubacterium hallii group and change in lower-limb lean mass (r = −0.323, p = 0.003).
Confidence Level
Moderate. Randomized, assessor-blinded, placebo/energy-controlled, and registered. However, per-group sample sizes after dropout were small (n = 18–22; 81 of 93 completed), duration was only 12 weeks, effect sizes/confidence intervals were not reported in the abstract, and participants were healthy Japanese older women, limiting generalizability. No retraction or corrections noted.
Study Flags
Red Flags
- •Small per-group sample after dropout (RT+HP n=18; overall 81/93 completed) and short 12-week duration
- •Effect sizes, absolute changes, and confidence intervals not reported in the abstract
- •Findings limited to healthy Japanese older women; not generalizable to men, frail elderly, or other populations
Surprising Findings
Gut microbiota composition did not change significantly after 12 weeks of resistance training and/or chicken meat intake, even after FDR correction.
Previous animal and human studies suggested exercise and meat intake can alter gut bacteria. This trial found no significant overall or individual taxa changes.
Practical Takeaways
For older women, combining resistance training (3 days/week, leg exercises) with chicken meat (110 g, ~22.5 g protein, 3 days/week) may produce greater gains in strength and lean mass than either alone.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 566 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This is a randomized controlled trial, which is like a fair test where people were put into groups by chance. It can show that resistance training and eating chicken can cause improvements in muscle strength and mass, but because it's a single small study, we can't be 100% sure it works for everyone.
Strengths
- Randomized controlled trial with computer-generated random allocation.
- Presence of control groups (sedentary and placebo) allowing comparison.
- Outcome assessors were blinded to group allocation.
Weaknesses
- Small sample size per group (18–22 completers), limiting statistical power.
- Single-blind design: participants were not blinded, which could influence behavior or diet.
- Baseline differences in lower limb and whole-body lean mass between some groups despite randomization.
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists studied 93 older women. Some did leg exercises, some ate chicken, some did both, and some did neither. They checked muscle strength, muscle mass, and gut bacteria.
Research results
After 12 weeks: leg training alone made muscles stronger; chicken alone increased whole-body lean mass; doing both gave the biggest increases in strength and lean mass. Gut bacteria overall did not change much. One gut bacteria group went down and leg lean mass went up, but the link was weak (r = −0.323). Exact muscle changes in kilograms or percent were not reported.
What this means - more context
This is not a disease-risk study, so there is no absolute risk increase to report. The abstract does not give exact kilograms or percent changes for muscle outcomes. For a person, it suggests adding chicken and resistance training may help maintain muscle, but the exact amount of benefit is not known from this summary. Gut bacteria changes were not significant after correction, so no clear harm or benefit there.
Investigated whether 12 weeks of resistance training combined with chicken meat intake increases muscle mass and strength in older women and whether gut microbiota changes underlie the effect.
In a randomized controlled trial of 93 older women (59–79 years; 81 completed), resistance training alone increased maximal muscle strength, chicken meat intake alone increased whole-body lean mass, and the combination produced greater increases in maximal muscle strength and whole-body lean mass than either alone. Gut microbiota beta-diversity and individual taxa after FDR correction did not significantly change. A weak negative correlation was found between decrease in Eubacterium hallii group and increase in lower-limb lean mass (r = −0.323, p = 0.003). No relative risks or absolute risk outcomes were reported; muscle effect sizes and absolute changes were not specified in the available text.
Methods Used
Randomized controlled trial; 93 community-dwelling Japanese women aged 59–79 allocated to sedentary control + placebo (Sed+PL), sedentary + chicken meat (Sed+HP), resistance training + placebo (RT+PL), or resistance training + chicken meat (RT+HP). Resistance training: 3 days/week for 12 weeks, 3 sets of 10 leg extensions and leg curls at 70% 1RM. Chicken meat: 110 g boiled chicken breast containing 22.5 g protein, 3 days/week for 12 weeks; placebo was an energy-matched protein-free carbohydrate food. Outcomes included DXA body composition, maximal knee extension strength, and 16S rRNA fecal microbiota. Assessors were blinded to allocation.
Main Finding
Combining 12 weeks of high-intensity resistance training (3 days/week) with chicken meat intake (110 g containing 22.5 g protein, 3 days/week) probably produces greater increases in maximal muscle strength and whole-body lean mass than either intervention alone in older women aged 59–79. The study did not report relative risks or absolute risk; muscle effect sizes and absolute changes were not specified in the available abstract. Gut microbiota composition did not significantly change before or after intervention in any group, and no individual taxa survived FDR correction. A weak negative correlation was observed between change in Eubacterium hallii group and change in lower-limb lean mass (r = −0.323, p = 0.003).
Confidence Level
Moderate. Randomized, assessor-blinded, placebo/energy-controlled, and registered. However, per-group sample sizes after dropout were small (n = 18–22; 81 of 93 completed), duration was only 12 weeks, effect sizes/confidence intervals were not reported in the abstract, and participants were healthy Japanese older women, limiting generalizability. No retraction or corrections noted.
Study Flags
Red Flags
- •Small per-group sample after dropout (RT+HP n=18; overall 81/93 completed) and short 12-week duration
- •Effect sizes, absolute changes, and confidence intervals not reported in the abstract
- •Findings limited to healthy Japanese older women; not generalizable to men, frail elderly, or other populations
Surprising Findings
Gut microbiota composition did not change significantly after 12 weeks of resistance training and/or chicken meat intake, even after FDR correction.
Previous animal and human studies suggested exercise and meat intake can alter gut bacteria. This trial found no significant overall or individual taxa changes.
Practical Takeaways
For older women, combining resistance training (3 days/week, leg exercises) with chicken meat (110 g, ~22.5 g protein, 3 days/week) may produce greater gains in strength and lean mass than either alone.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 566 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This is a randomized controlled trial, which is like a fair test where people were put into groups by chance. It can show that resistance training and eating chicken can cause improvements in muscle strength and mass, but because it's a single small study, we can't be 100% sure it works for everyone.
Strengths
- Randomized controlled trial with computer-generated random allocation.
- Presence of control groups (sedentary and placebo) allowing comparison.
- Outcome assessors were blinded to group allocation.
Weaknesses
- Small sample size per group (18–22 completers), limiting statistical power.
- Single-blind design: participants were not blinded, which could influence behavior or diet.
- Baseline differences in lower limb and whole-body lean mass between some groups despite randomization.
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study was well-designed with random groups and blinded assessors, but it was small and people knew if they were exercising or eating chicken, which could affect some results. Also, some groups started with different muscle mass, so we should be cautious about how much we trust the findings.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
77 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=93)+7.4/20
- Follow-up+10/10
100 / 100
46 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 566 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Randomization allows causal inference for the effects of resistance training and/or chicken meat on muscle strength and mass. However, small sample size per group, single-blind design (participants not blinded), baseline differences in lean body mass between some groups, short 12-week duration, and multiple comparisons limit the strength of causal conclusions. Causation cannot be established for the gut microbiome mechanism because no significant microbiota changes were observed and only a weak correlation was found.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding disclosures are present in the provided text, and the excerpt appears truncated, so COI/funding status cannot be fully determined.
Independent Analysis Safeguards
- Assessors blinded to group allocation
- Randomized controlled trial design
The provided text does not include a conflict of interest or funding statement; it appears truncated before acknowledgments. No industry funding or author COI can be confirmed or ruled out. The chicken meat intervention could imply possible industry involvement, but no provider or funder is disclosed.
Standing
The people behind it
The researchers who wrote the study this analysis is built on.
Authored by
12 researchersIf this is your work, this is how we attribute it on Fit Body Science. Masataka Uchida is listed as the lead author.