Study analysis · The Journal of Nutrition · 2022
Eating an avocado a day for 12 weeks didn't improve insulin sensitivity—but it did lower one inflammation marker, and the study had a big catch.
In adults with overweight and insulin resistance, one avocado daily for 12 weeks did not significantly improve the main insulin sensitivity measure, but it trended toward better blood sugar and significantly lowered one inflammation marker at 12 weeks.
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 randomly assigned people to eat avocado or a control food, so it's a strong way to test cause and effect. But the main test didn't show a clear difference, so we can't say avocado definitely improves health—it only hints at possible small benefits that need more research.
What’s the bottom line?
Researchers tested whether eating one avocado every day for 12 weeks helped overweight or obese adults with insulin resistance. The main insulin sensitivity measure did not improve significantly, but there were small trends toward better blood sugar and inflammation markers.
How strong is this study?
The study was well-designed because it was randomized and controlled, but it had some problems: people knew what they were eating, many dropped out, and they tested many things, so some findings could be by chance. That means we should trust the big picture more than the small details.
0 / 100
- COI disclosureconflicts of interest not disclosed
- 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
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- 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 572 / 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. RCT design supports causal inference, but single-blinding, free-living setting, per-protocol analysis, high attrition, and multiple comparisons limit certainty. The primary outcome was not significant, so causal claims for glucose control are not supported. Causal claims for secondary outcomes are tentative and require replication.
Major COI
Major conflicts that significantly reduce study credibility
The study received in-kind support from the Hass Avocado Board, the industry board for the product tested, but no explicit conflict of interest or funding statement is present in the provided text. The funder's role in design, analysis, or publication is not described.
Funders
Conflict Details
Hass Avocado Board: Provided Hass avocados for the intervention
Independent Analysis Safeguards
- Statistician-blinded
No explicit COI or funding section is included in the provided text; only in-kind support from the Hass Avocado Board is mentioned. The funder's role in study design, data analysis, or publication decisions is not described. The primary outcome (MISI) did not reach statistical significance, but some secondary outcomes favored avocado. The industry sponsorship may introduce bias risk.
Key takeaways
- 01
The main insulin sensitivity measure did not improve more with avocado than control (P=0.1092).
- 02
HbA1c was 0.097 percentage points lower with avocado, an absolute difference, but not statistically significant (P=0.0632).
- 03
Fasting insulin trended lower (P=0.0855).
- 04
hsCRP was 0.47 mg/L lower at 12 weeks (absolute difference; P=0.0418), but change from baseline was not significant (P=0.1748).
- 05
No weight gain occurred.
- 06
The differences are small in absolute terms: HbA1c was 0.097 percentage points lower with avocado (an absolute difference less than 0.1%), and hsCRP was 0.47 mg/L lower (absolute difference).
- 07
The study did not report absolute risk per 1,000 people because it did not track disease events.
- 08
These changes were mostly not statistically significant, except hsCRP at 12 weeks, and the primary insulin sensitivity measure did not improve.
Surprising findings
- The primary outcome—insulin sensitivity—was null, despite avocado being rich in MUFA, PUFA, and fiber.Previous shorter studies and meta-analyses suggested replacing carbs with unsaturated fats improves insulin sensitivity. This 12-week RCT in insulin-resistant adults did not confirm that for avocado.
- hsCRP was significantly lower at 12 weeks with avocado, but the change from baseline was not significant.A P=0.0418 for the 12-week comparison sounds like a win, but the change-from-baseline P=0.1748 suggests the difference may be driven by baseline imbalances or noise.
- No weight or body composition change despite daily avocado addition.Avocados are calorie-dense; many assume daily consumption would lead to weight gain. This study found no such effect over 12 weeks.
- Participants were more likely to add avocado than to replace carbohydrate calories.The study design assumed carbohydrate replacement, but free-living behavior led to addition instead—potentially attenuating the effects.
Practical takeaways
Don't rely on avocado alone to improve insulin sensitivity or blood sugar control; the primary outcome was null.
This was a 12-week study in adults with overweight/obesity and insulin resistance; longer or different populations may respond differently.
high confidenceIf you enjoy avocado, adding one daily is unlikely to cause weight gain in the short term and may improve diet quality (more fiber, folate, vegetables).
The study was free-living and self-reported; participants often added avocado rather than replacing carbs, and weight effects beyond 12 weeks are unknown.
medium confidencePay attention to absolute differences, not just P-values: HbA1c dropped by only 0.097 percentage points—less than 0.1%.
The HbA1c difference was not statistically significant, and the confidence interval includes zero.
high confidenceFor inflammation, don't overinterpret the hsCRP finding: it was significant at 12 weeks but not for change from baseline.
Multiple secondary outcomes were tested, increasing the chance of a false positive.
medium confidenceWhy this study matters
Primary outcome was a bust: no insulin sensitivity boost
The study's main goal was change in Matsuda Insulin Sensitivity Index (MISI). Avocado vs control showed no statistically significant difference (P=0.1092), though the effect size was small-to-medium (Cohen's d=0.305; 95% CI: -0.103 to 0.715). The absolute mean difference in MISI was not specified in the summary.
Avocados are often marketed as a superfood for blood sugar and insulin. This RCT in people with insulin resistance found no significant improvement in the gold-standard-ish measure.
HbA1c trend: tiny absolute drop, not statistically significant
Avocado led to a trend toward lower HbA1c: absolute mean difference -0.097 percentage points (95% CI: -0.198 to 0.004; P=0.0632; Cohen's d=-0.399). That's less than 0.1 percentage point—very small in absolute terms.
People with prediabetes often obsess over HbA1c. A 0.097-point drop is not clinically meaningful for most, and it wasn't statistically significant.
hsCRP lower at 12 weeks—but change from baseline wasn't significant
At 12 weeks, hsCRP was 3.20 mg/L with avocado vs 3.67 mg/L with control—an absolute difference of about 0.47 mg/L (P=0.0418). However, the change from baseline between groups was not significant (P=0.1748; Cohen's d=-0.238).
Inflammation is a hot topic. A significant cross-sectional difference at 12 weeks sounds impressive, but the change-from-baseline analysis is less so. This is a classic statistical fragility.
No weight gain despite adding avocado daily
Participants in the avocado arm increased total fat, MUFA, PUFA, fiber, folate, and vegetable intake, yet showed no significant changes in body weight, BMI, or body composition (P>0.05).
Many people fear that adding a calorie-dense avocado will cause weight gain. In this 12-week free-living study, it didn't.
People often added avocado instead of replacing carbs
The study aimed to replace carbohydrate energy with avocado energy, but dietary data suggested participants were more likely to add avocado rather than swap out carbs. Carbohydrate intake remained relatively stable. This may have diluted the effect on insulin sensitivity.
Real-world behavior often diverges from study instructions. This is a key limitation and a lesson for anyone trying to change their diet.
Lipoprotein trends: small LDL and chylomicron/VLDL particles
Total LDL particle concentration was 968 vs 1000 nmol/L (P=0.0694) and small chylomicron/VLDL particles were 24.7 vs 27.5 nmol/L (P=0.0638) after avocado vs control. Both were non-significant trends with small-to-medium effect sizes.
Lipoprotein particles are emerging risk markers. These trends suggest possible cardiovascular benefits, but they are not definitive.
Dropout and per-protocol analysis weaken confidence
124 enrolled, 93 evaluable—a 21.8% dropout. The analysis was per-protocol, not intention-to-treat, and multiple secondary outcomes were tested, increasing risk of false positives.
A 21.8% dropout is common but can bias results. Combined with a null primary outcome, it means all positive findings should be interpreted cautiously.
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
Researchers tested whether eating one avocado every day for 12 weeks helped overweight or obese adults with insulin resistance. The main insulin sensitivity measure did not improve significantly, but there were small trends toward better blood sugar and inflammation markers.
Research results
The main insulin sensitivity measure did not improve more with avocado than control (P=0.1092). HbA1c was 0.097 percentage points lower with avocado, an absolute difference, but not statistically significant (P=0.0632). Fasting insulin trended lower (P=0.0855). hsCRP was 0.47 mg/L lower at 12 weeks (absolute difference; P=0.0418), but change from baseline was not significant (P=0.1748). No weight gain occurred.
What this means - more context
The differences are small in absolute terms: HbA1c was 0.097 percentage points lower with avocado (an absolute difference less than 0.1%), and hsCRP was 0.47 mg/L lower (absolute difference). The study did not report absolute risk per 1,000 people because it did not track disease events. These changes were mostly not statistically significant, except hsCRP at 12 weeks, and the primary insulin sensitivity measure did not improve.
Assess replacing carbohydrate energy with avocado energy for 12 weeks on glucose homeostasis and cardiometabolic risk factors in overweight/obese adults with insulin resistance. Not retracted; no corrections reported.
In 93 evaluable adults with overweight/obesity and insulin resistance, 12 weeks of daily avocado vs energy-matched low-fat/low-fiber control did not significantly improve the primary outcome, Matsuda Insulin Sensitivity Index (P=0.1092). Trends favored avocado for HbA1c (absolute difference -0.097 percentage points; P=0.0632), fasting insulin (P=0.0855), and HOMA-IR (P=0.1098). hsCRP was significantly lower at 12 weeks (absolute difference ~0.47 mg/L; P=0.0418), but change from baseline was not significant (P=0.1748). VCAM-1 change differed (P=0.0471). No weight or body composition change. No retraction or corrections reported.
Methods Used
Single-center, randomized, 2-arm, controlled, 12-week parallel trial. 124 enrolled; 93 evaluable (39 male/54 female; mean age 42 y; BMI 32.6; HOMA-IR 2.7). Avocado (1 Hass/day) vs energy-matched low-fat/low-fiber control food. Primary outcome: change in Matsuda Insulin Sensitivity Index (MISI); secondary outcomes included glycemic, lipid, endothelial, and inflammation markers. ANCOVA with baseline covariate.
Main Finding
Primary outcome: MISI change did not differ significantly between avocado and control (P=0.1092; Cohen's d=0.305; absolute mean difference not specified). Secondary outcomes: HbA1c trend lower with avocado (absolute mean difference -0.097 percentage points; 95% CI -0.198 to 0.004; P=0.0632; d=-0.399), fasting insulin trend lower (P=0.0855; d≤0.2), hsCRP significantly lower at 12 wk (3.20 vs 3.67 mg/L; absolute difference ~0.47 mg/L; P=0.0418) but change-from-baseline not significant (P=0.1748; d=-0.238), VCAM-1 change differed (P=0.0471), and LDL/small chylomicron-VLDL particles trended lower. No weight or body composition change. No absolute risk per 1,000 reported because no disease events were measured.
Confidence Level
Moderate. Randomized, pre-registered, effect sizes and CIs reported. Limitations: primary outcome null; per-protocol analysis; 21.8% dropout; multiple secondary outcomes; free-living adherence and participants often added avocado rather than fully replacing carbohydrate.
Study Flags
Red Flags
- •Primary outcome (MISI) not statistically significant
- •Per-protocol analysis with 21.8% dropout and multiple secondary comparisons
- •Free-living self-report and incomplete carbohydrate replacement may attenuate effects
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
The primary outcome—insulin sensitivity—was null, despite avocado being rich in MUFA, PUFA, and fiber.
Previous shorter studies and meta-analyses suggested replacing carbs with unsaturated fats improves insulin sensitivity. This 12-week RCT in insulin-resistant adults did not confirm that for avocado.
Practical Takeaways
Don't rely on avocado alone to improve insulin sensitivity or blood sugar control; the primary outcome was null.
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 572 / 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
High probability
on the GRADE evidence scale
This study randomly assigned people to eat avocado or a control food, so it's a strong way to test cause and effect. But the main test didn't show a clear difference, so we can't say avocado definitely improves health—it only hints at possible small benefits that need more research.
Major conflicts — industry funding with significant control over the research. Reporting score and overall score cap have been reduced.
Strengths
- Randomized controlled trial design
- Parallel two-arm controlled trial
- 12-week intervention duration
Weaknesses
- Single-blind design (participants not blinded)
- Per-protocol analysis rather than intent-to-treat
- High dropout rate (21.8%)
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Researchers tested whether eating one avocado every day for 12 weeks helped overweight or obese adults with insulin resistance. The main insulin sensitivity measure did not improve significantly, but there were small trends toward better blood sugar and inflammation markers.
Research results
The main insulin sensitivity measure did not improve more with avocado than control (P=0.1092). HbA1c was 0.097 percentage points lower with avocado, an absolute difference, but not statistically significant (P=0.0632). Fasting insulin trended lower (P=0.0855). hsCRP was 0.47 mg/L lower at 12 weeks (absolute difference; P=0.0418), but change from baseline was not significant (P=0.1748). No weight gain occurred.
What this means - more context
The differences are small in absolute terms: HbA1c was 0.097 percentage points lower with avocado (an absolute difference less than 0.1%), and hsCRP was 0.47 mg/L lower (absolute difference). The study did not report absolute risk per 1,000 people because it did not track disease events. These changes were mostly not statistically significant, except hsCRP at 12 weeks, and the primary insulin sensitivity measure did not improve.
Assess replacing carbohydrate energy with avocado energy for 12 weeks on glucose homeostasis and cardiometabolic risk factors in overweight/obese adults with insulin resistance. Not retracted; no corrections reported.
In 93 evaluable adults with overweight/obesity and insulin resistance, 12 weeks of daily avocado vs energy-matched low-fat/low-fiber control did not significantly improve the primary outcome, Matsuda Insulin Sensitivity Index (P=0.1092). Trends favored avocado for HbA1c (absolute difference -0.097 percentage points; P=0.0632), fasting insulin (P=0.0855), and HOMA-IR (P=0.1098). hsCRP was significantly lower at 12 weeks (absolute difference ~0.47 mg/L; P=0.0418), but change from baseline was not significant (P=0.1748). VCAM-1 change differed (P=0.0471). No weight or body composition change. No retraction or corrections reported.
Methods Used
Single-center, randomized, 2-arm, controlled, 12-week parallel trial. 124 enrolled; 93 evaluable (39 male/54 female; mean age 42 y; BMI 32.6; HOMA-IR 2.7). Avocado (1 Hass/day) vs energy-matched low-fat/low-fiber control food. Primary outcome: change in Matsuda Insulin Sensitivity Index (MISI); secondary outcomes included glycemic, lipid, endothelial, and inflammation markers. ANCOVA with baseline covariate.
Main Finding
Primary outcome: MISI change did not differ significantly between avocado and control (P=0.1092; Cohen's d=0.305; absolute mean difference not specified). Secondary outcomes: HbA1c trend lower with avocado (absolute mean difference -0.097 percentage points; 95% CI -0.198 to 0.004; P=0.0632; d=-0.399), fasting insulin trend lower (P=0.0855; d≤0.2), hsCRP significantly lower at 12 wk (3.20 vs 3.67 mg/L; absolute difference ~0.47 mg/L; P=0.0418) but change-from-baseline not significant (P=0.1748; d=-0.238), VCAM-1 change differed (P=0.0471), and LDL/small chylomicron-VLDL particles trended lower. No weight or body composition change. No absolute risk per 1,000 reported because no disease events were measured.
Confidence Level
Moderate. Randomized, pre-registered, effect sizes and CIs reported. Limitations: primary outcome null; per-protocol analysis; 21.8% dropout; multiple secondary outcomes; free-living adherence and participants often added avocado rather than fully replacing carbohydrate.
Study Flags
Red Flags
- •Primary outcome (MISI) not statistically significant
- •Per-protocol analysis with 21.8% dropout and multiple secondary comparisons
- •Free-living self-report and incomplete carbohydrate replacement may attenuate effects
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
The primary outcome—insulin sensitivity—was null, despite avocado being rich in MUFA, PUFA, and fiber.
Previous shorter studies and meta-analyses suggested replacing carbs with unsaturated fats improves insulin sensitivity. This 12-week RCT in insulin-resistant adults did not confirm that for avocado.
Practical Takeaways
Don't rely on avocado alone to improve insulin sensitivity or blood sugar control; the primary outcome was null.
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 572 / 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
High probability
on the GRADE evidence scale
This study randomly assigned people to eat avocado or a control food, so it's a strong way to test cause and effect. But the main test didn't show a clear difference, so we can't say avocado definitely improves health—it only hints at possible small benefits that need more research.
Major conflicts — industry funding with significant control over the research. Reporting score and overall score cap have been reduced.
Strengths
- Randomized controlled trial design
- Parallel two-arm controlled trial
- 12-week intervention duration
Weaknesses
- Single-blind design (participants not blinded)
- Per-protocol analysis rather than intent-to-treat
- High dropout rate (21.8%)
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study was well-designed because it was randomized and controlled, but it had some problems: people knew what they were eating, many dropped out, and they tested many things, so some findings could be by chance. That means we should trust the big picture more than the small details.
0 / 100
- COI disclosureconflicts of interest not disclosed
- 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
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- 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 572 / 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. RCT design supports causal inference, but single-blinding, free-living setting, per-protocol analysis, high attrition, and multiple comparisons limit certainty. The primary outcome was not significant, so causal claims for glucose control are not supported. Causal claims for secondary outcomes are tentative and require replication.
Major COI
Major conflicts that significantly reduce study credibility
The study received in-kind support from the Hass Avocado Board, the industry board for the product tested, but no explicit conflict of interest or funding statement is present in the provided text. The funder's role in design, analysis, or publication is not described.
Funders
Conflict Details
Hass Avocado Board: Provided Hass avocados for the intervention
Independent Analysis Safeguards
- Statistician-blinded
No explicit COI or funding section is included in the provided text; only in-kind support from the Hass Avocado Board is mentioned. The funder's role in study design, data analysis, or publication decisions is not described. The primary outcome (MISI) did not reach statistical significance, but some secondary outcomes favored avocado. The industry sponsorship may introduce bias risk.
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.
- Conflicting evidence
Evidence points in both directions — no clear conclusion yet.
Evidence
Authored by
5 researchersIf this is your work, this is how we attribute it on Fit Body Science. Xuhuiqun Zhang is listed as the lead author.