Study analysis · The Journal of Nutrition · 2020
Eating a daily avocado changed gut bacteria and bile acids in 12 weeks — but not weight, and the stats may not survive scrutiny.
In adults with overweight or obesity, eating an avocado daily for 12 weeks shifted the mix of gut bacteria and stool chemicals in relative terms, but it didn't change body weight and the findings are early.
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 study is a randomized controlled trial, which is one of the best ways to test if something causes a change. They randomly assigned people to eat avocado or not, so we can be fairly confident that avocado caused the differences in gut bacteria and metabolites. However, these were not the main outcomes, and some results were not strong after statistical correction, so we should be cautious.
What’s the bottom line?
Scientists gave adults with overweight or obesity a daily meal with or without avocado for 12 weeks. They checked gut bacteria and chemicals in stool to see if avocado made a difference.
How strong is this study?
The study was well-designed: people were randomly put into groups, meals were controlled, and measurements were done with fancy lab tests. But the researchers only blinded themselves, not the participants, and some results were only seen in people who followed the diet perfectly. Also, they tested many things without adjusting for chance, so some findings might be false positives.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
81 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=163)+11.2/20
- 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 560 / 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. The study is an RCT, so it can establish causation for the intervention effect. However, the outcomes analyzed here are secondary and exploratory, with no correction for multiple comparisons, and some results are per-protocol only. Participant blinding was not used (only investigator-blinded), and compliance was self-reported. Thus, causal claims should be tempered.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement was present in the provided text, so potential conflicts cannot be assessed.
Independent Analysis Safeguards
- Investigator-blinded trial
- Randomization conducted by a research staff member not involved in data collection
- Trial registered at clinicaltrials.gov (NCT02740439)
The provided text includes no conflict of interest, funding, or author affiliation section. It appears to be an academic study conducted at the University of Illinois, but funding source and author disclosures are not included in the excerpt.
Key takeaways
- 01
Compared with the control group, the avocado group had 26% to 65% higher relative amounts of three gut bacteria (Faecalibacterium, Lachnospira, Alistipes), 18% higher relative fecal acetate, 70% higher relative stearic acid, and 98% higher relative palmitic acid (measured in only 45 people).
- 02
They also had 91% lower relative cholic acid and 57% lower relative chenodeoxycholic acid.
- 03
Body weight was about the same: 96.2 kg in the avocado group vs 96.0 kg in the control group.
- 04
These are relative differences in bacteria and chemicals, not absolute amounts.
- 05
The study did not report absolute bacterial abundance or metabolite concentrations, so we cannot say exactly how many more bacteria or how much more acetate a person would have.
- 06
For weight, the absolute difference was only 0.2 kg, which is not meaningful.
- 07
The findings are early and could be due to chance because many comparisons were made.
Surprising findings
- Body weight did not change despite daily avocado.Avocado is commonly promoted as a weight-loss-friendly food because of fiber and satiety, yet the absolute difference was only 0.2 kg and not statistically significant.
- Bile acids were lower, not higher, with avocado.Avocado is rich in fat, and dietary fat often increases bile acid secretion; here cholic acid was 91% lower relative and chenodeoxycholic acid 57% lower relative.
- Fecal fatty acids increased by 70% and 98% relative in a subset.It suggests more dietary fat reached the colon or was excreted, which is counterintuitive for a food often associated with improved lipid profiles.
- The findings did not survive multiple-comparison correction.The headline percentages are eye-catching, but the study itself notes they were exploratory and did not hold after FDR correction.
- Intent-to-treat and per-protocol results diverged.In intent-to-treat, Alistipes and Ruminococcus were greater and alpha diversity did not differ (P = 0.13), while per-protocol showed alpha diversity differences — showing how much compliance and analysis choice matter.
Practical takeaways
Eat avocado for fiber and monounsaturated fats, but don't expect it to cause weight loss on its own.
This was a 12-week isocaloric trial in adults with overweight/obesity; weight was not different between groups.
medium confidenceIf you're interested in gut health, daily avocado may shift gut bacteria and metabolites in relative terms — but the evidence is early.
Findings were secondary/exploratory, did not survive FDR correction, and absolute changes are unknown.
low confidenceBe skeptical of headlines citing '91% lower bile acid' or '98% higher palmitic acid' from this study.
These are relative differences, not absolute changes, and the fatty acid subset was only n=45.
high confidenceKeep overall calorie balance in mind; replacing a meal with an avocado meal did not change weight in this study.
Real-world diets are less controlled than provided study meals, and self-reported intake has limitations.
medium confidenceWhy this study matters
Avocado feeds fiber-fermenting gut bugs
In the per-protocol analysis, the avocado group had 26% to 65% higher relative abundance of Faecalibacterium, Lachnospira, and Alistipes compared with the control group. Alpha diversity was also greater in the avocado group. These are relative between-group differences, and the findings were secondary/exploratory and did not hold after FDR correction.
Gut health is a huge wellness topic, and avocado is a popular 'superfood' — this gives a concrete, if preliminary, microbial signal.
Acetate bump: 18% relative higher
The avocado group had 18% greater fecal acetate concentrations than the control group in per-protocol analysis. Acetate is a short-chain fatty acid produced when gut bacteria ferment fiber. This is a relative difference, absolute concentrations were not reported, and it was an exploratory outcome.
Short-chain fatty acids are linked to gut and metabolic health, so a food-based way to raise acetate is appealing.
Bile acids plummet in relative terms
Cholic acid was 91% lower and chenodeoxycholic acid was 57% lower in the avocado group compared with control — again, relative between-group differences. Secondary bile acids deoxycholic and lithocholic acid were numerically lower by 23% and 14%. Absolute values were not reported.
Bile acids affect fat digestion and gut microbes, and lower levels could be beneficial — but the 91% number can easily be misread as an absolute risk drop.
Fecal fats up — but measured in only 45 people
The avocado group had 70% higher relative stearic acid and 98% higher relative palmitic acid concentrations in a subset of 45 participants. These are exploratory fecal fatty acid outcomes, and the small subset limits confidence.
It suggests avocado fats may reach the colon in measurable ways, but the small sample makes it a weak signal.
No weight change: 96.2 vs 96.0 kg
Body weight did not differ between groups at 12 weeks: control 96.0 ± 2.68 kg vs avocado 96.2 ± 2.76 kg; P = 0.95. That is an absolute difference of only 0.2 kg, which is not meaningful.
Avocado is often marketed for weight loss or satiety, but this isocaloric trial found no weight benefit.
The fine print: exploratory and no FDR correction
The microbial and metabolite outcomes were secondary/exploratory and did not remain significant after Benjamini-Hochberg false discovery rate correction. The study also did not report absolute differences for microbiota or metabolites.
This is a masterclass in why headlines should not treat every statistically significant secondary outcome as definitive.
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 gave adults with overweight or obesity a daily meal with or without avocado for 12 weeks. They checked gut bacteria and chemicals in stool to see if avocado made a difference.
Research results
Compared with the control group, the avocado group had 26% to 65% higher relative amounts of three gut bacteria (Faecalibacterium, Lachnospira, Alistipes), 18% higher relative fecal acetate, 70% higher relative stearic acid, and 98% higher relative palmitic acid (measured in only 45 people). They also had 91% lower relative cholic acid and 57% lower relative chenodeoxycholic acid. Body weight was about the same: 96.2 kg in the avocado group vs 96.0 kg in the control group.
What this means - more context
These are relative differences in bacteria and chemicals, not absolute amounts. The study did not report absolute bacterial abundance or metabolite concentrations, so we cannot say exactly how many more bacteria or how much more acetate a person would have. For weight, the absolute difference was only 0.2 kg, which is not meaningful. The findings are early and could be due to chance because many comparisons were made.
To evaluate the impact of daily avocado consumption on gastrointestinal microbiota and microbial metabolites as secondary outcomes of the PATH randomized controlled trial in adults with overweight or obesity.
In 163 adults with overweight or obesity, 12 weeks of daily avocado (140-175 g) versus an isocaloric control meal increased fecal microbiota alpha diversity and enriched relative abundances of Faecalibacterium, Lachnospira, and Alistipes by 26% to 65% (relative between-group differences; secondary/exploratory). Fecal acetate was 18% higher relative; stearic acid was 70% higher and palmitic acid 98% higher relative (subset n=45); cholic acid was 91% lower and chenodeoxycholic acid 57% lower relative. Body weight did not differ (96.2 vs 96.0 kg; P=0.95). Absolute differences in microbial and metabolite measures were not reported; findings were exploratory and did not hold after multiple-comparison correction.
Methods Used
Randomized, investigator-blinded, parallel-arm 12-week trial; 163 adults aged 25-45 years with BMI ≥25.0 were batch randomized to isocaloric meals with avocado (175 g/day men; 140 g/day women) or without avocado. Fecal microbiota assessed by 16S rRNA gene (V4) sequencing; fecal fatty acids and bile acids quantified by GC and LC-MS. Per-protocol (≥80% meal consumption) and intent-to-treat analyses used univariate ANOVA and Mann-Whitney U tests; bivariate correlations examined links between bacteria, metabolites, and health markers.
Main Finding
The primary outcomes of the PATH trial were glycemic control and abdominal adiposity; this report covers secondary outcomes. Daily avocado consumption led to relative between-group increases in select gut bacteria (26-65%), fecal acetate (18% relative), stearic acid (70% relative), and palmitic acid (98% relative), and relative decreases in cholic acid (91%) and chenodeoxycholic acid (57%). Body weight did not differ (absolute difference 0.2 kg; P=0.95). Absolute effect sizes for microbiota and metabolite outcomes were not reported, and findings were exploratory without multiple-comparison correction.
Confidence Level
Moderate-low: randomized controlled design with investigator blinding, but outcomes were secondary/exploratory and did not remain significant after FDR correction; fatty acid analyses used a small subset (n=45); dietary intake and meal compliance were self-reported; participants were adults with overweight/obesity without chronic disease, limiting generalizability. No retraction or corrections were identified.
Study Flags
Red Flags
- •Secondary/exploratory outcomes; no correction for multiple comparisons (findings did not hold after FDR)
- •Fatty acid analyses in subset n=45; self-reported diet and meal compliance
- •Limited generalizability: overweight/obese adults without chronic disease; absolute effect sizes not reported
Surprising Findings
Body weight did not change despite daily avocado.
Avocado is commonly promoted as a weight-loss-friendly food because of fiber and satiety, yet the absolute difference was only 0.2 kg and not statistically significant.
Practical Takeaways
Eat avocado for fiber and monounsaturated fats, but don't expect it to cause weight loss on its own.
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 560 / 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 study is a randomized controlled trial, which is one of the best ways to test if something causes a change. They randomly assigned people to eat avocado or not, so we can be fairly confident that avocado caused the differences in gut bacteria and metabolites. However, these were not the main outcomes, and some results were not strong after statistical correction, so we should be cautious.
Strengths
- Randomized controlled trial design with parallel arms
- Groups matched on age, sex, visceral adiposity, and fasting glucose
- Isocaloric meals with identical macronutrient composition except avocado
Weaknesses
- Microbiota and metabolite outcomes were secondary and exploratory
- No adjustment for multiple comparisons for many findings (FDR not held)
- Only investigator-blinded, participants not blinded
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists gave adults with overweight or obesity a daily meal with or without avocado for 12 weeks. They checked gut bacteria and chemicals in stool to see if avocado made a difference.
Research results
Compared with the control group, the avocado group had 26% to 65% higher relative amounts of three gut bacteria (Faecalibacterium, Lachnospira, Alistipes), 18% higher relative fecal acetate, 70% higher relative stearic acid, and 98% higher relative palmitic acid (measured in only 45 people). They also had 91% lower relative cholic acid and 57% lower relative chenodeoxycholic acid. Body weight was about the same: 96.2 kg in the avocado group vs 96.0 kg in the control group.
What this means - more context
These are relative differences in bacteria and chemicals, not absolute amounts. The study did not report absolute bacterial abundance or metabolite concentrations, so we cannot say exactly how many more bacteria or how much more acetate a person would have. For weight, the absolute difference was only 0.2 kg, which is not meaningful. The findings are early and could be due to chance because many comparisons were made.
To evaluate the impact of daily avocado consumption on gastrointestinal microbiota and microbial metabolites as secondary outcomes of the PATH randomized controlled trial in adults with overweight or obesity.
In 163 adults with overweight or obesity, 12 weeks of daily avocado (140-175 g) versus an isocaloric control meal increased fecal microbiota alpha diversity and enriched relative abundances of Faecalibacterium, Lachnospira, and Alistipes by 26% to 65% (relative between-group differences; secondary/exploratory). Fecal acetate was 18% higher relative; stearic acid was 70% higher and palmitic acid 98% higher relative (subset n=45); cholic acid was 91% lower and chenodeoxycholic acid 57% lower relative. Body weight did not differ (96.2 vs 96.0 kg; P=0.95). Absolute differences in microbial and metabolite measures were not reported; findings were exploratory and did not hold after multiple-comparison correction.
Methods Used
Randomized, investigator-blinded, parallel-arm 12-week trial; 163 adults aged 25-45 years with BMI ≥25.0 were batch randomized to isocaloric meals with avocado (175 g/day men; 140 g/day women) or without avocado. Fecal microbiota assessed by 16S rRNA gene (V4) sequencing; fecal fatty acids and bile acids quantified by GC and LC-MS. Per-protocol (≥80% meal consumption) and intent-to-treat analyses used univariate ANOVA and Mann-Whitney U tests; bivariate correlations examined links between bacteria, metabolites, and health markers.
Main Finding
The primary outcomes of the PATH trial were glycemic control and abdominal adiposity; this report covers secondary outcomes. Daily avocado consumption led to relative between-group increases in select gut bacteria (26-65%), fecal acetate (18% relative), stearic acid (70% relative), and palmitic acid (98% relative), and relative decreases in cholic acid (91%) and chenodeoxycholic acid (57%). Body weight did not differ (absolute difference 0.2 kg; P=0.95). Absolute effect sizes for microbiota and metabolite outcomes were not reported, and findings were exploratory without multiple-comparison correction.
Confidence Level
Moderate-low: randomized controlled design with investigator blinding, but outcomes were secondary/exploratory and did not remain significant after FDR correction; fatty acid analyses used a small subset (n=45); dietary intake and meal compliance were self-reported; participants were adults with overweight/obesity without chronic disease, limiting generalizability. No retraction or corrections were identified.
Study Flags
Red Flags
- •Secondary/exploratory outcomes; no correction for multiple comparisons (findings did not hold after FDR)
- •Fatty acid analyses in subset n=45; self-reported diet and meal compliance
- •Limited generalizability: overweight/obese adults without chronic disease; absolute effect sizes not reported
Surprising Findings
Body weight did not change despite daily avocado.
Avocado is commonly promoted as a weight-loss-friendly food because of fiber and satiety, yet the absolute difference was only 0.2 kg and not statistically significant.
Practical Takeaways
Eat avocado for fiber and monounsaturated fats, but don't expect it to cause weight loss on its own.
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 560 / 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 study is a randomized controlled trial, which is one of the best ways to test if something causes a change. They randomly assigned people to eat avocado or not, so we can be fairly confident that avocado caused the differences in gut bacteria and metabolites. However, these were not the main outcomes, and some results were not strong after statistical correction, so we should be cautious.
Strengths
- Randomized controlled trial design with parallel arms
- Groups matched on age, sex, visceral adiposity, and fasting glucose
- Isocaloric meals with identical macronutrient composition except avocado
Weaknesses
- Microbiota and metabolite outcomes were secondary and exploratory
- No adjustment for multiple comparisons for many findings (FDR not held)
- Only investigator-blinded, participants not blinded
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study was well-designed: people were randomly put into groups, meals were controlled, and measurements were done with fancy lab tests. But the researchers only blinded themselves, not the participants, and some results were only seen in people who followed the diet perfectly. Also, they tested many things without adjusting for chance, so some findings might be false positives.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
81 / 100
- Randomization+20/20
- Blinding+9/15
- Control group+15/15
- Sample size (n=163)+11.2/20
- 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 560 / 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. The study is an RCT, so it can establish causation for the intervention effect. However, the outcomes analyzed here are secondary and exploratory, with no correction for multiple comparisons, and some results are per-protocol only. Participant blinding was not used (only investigator-blinded), and compliance was self-reported. Thus, causal claims should be tempered.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement was present in the provided text, so potential conflicts cannot be assessed.
Independent Analysis Safeguards
- Investigator-blinded trial
- Randomization conducted by a research staff member not involved in data collection
- Trial registered at clinicaltrials.gov (NCT02740439)
The provided text includes no conflict of interest, funding, or author affiliation section. It appears to be an academic study conducted at the University of Illinois, but funding source and author disclosures are not included in the excerpt.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
1 video from Thomas DeLauer cite this study, drawing 1 claim from it.
- Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence
Authored by
10 researchersIf this is your work, this is how we attribute it on Fit Body Science. Sharon V. Thompson is listed as the lead author.
- University of Illinois Urbana-Champaign
Cited in 1 claim · 1 video