Study analysis · Brain, behavior, and immunity · 2025
Keto diet made people more anxious—according to mice.
Eating Mediterranean food made people less depressed, while keto made them less impulsive—but their gut bacteria made mice anxious.
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 found that people who ate the Mediterranean diet felt less sad than those on the keto diet, but it wasn't a big or perfect test. It also gave mouse poop from people to mice and saw the mice got anxious — which is interesting, but doesn't prove the same thing happens in humans.
What’s the bottom line?
Scientists tested two diets — one high-fat (keto) and one plant-based (Mediterranean) — on people with obesity to see how they affect mood and behavior, then tested the gut bacteria from these people in mice.
How strong is this study?
The study tried to be fair by randomly assigning people to diets, which is good. But lots of people dropped out, and we don't know if they knew which diet they were on — so the results might be skewed. That means we can't fully trust it yet.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
63 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=64)+5.5/20
- Follow-up+10/10
100 / 100
54 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
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 556 / 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 supports causal inference, but blinding is unknown and attrition reduced sample size, which may introduce bias and limit confidence in causal claims.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding statements were disclosed in the provided text; study appears independently conducted.
The study lacks any declared funding sources or conflict of interest statement, which is a limitation for transparency. However, no evidence of industry influence, author affiliations with commercial entities, or funder involvement was found in the provided text.
Key takeaways
- 01
The Mediterranean diet made people 32% less depressed; keto made them 14% less depressed but reduced impulsive behavior.
- 02
Mice given keto gut bacteria became anxious and had higher brain levels of taurine, alanine, and betaine.
- 03
Yes — the difference in depression improvement (32% vs.
- 04
14%) is meaningful and suggests diet choice can strongly impact mood in obese adults.
Surprising findings
- Fecal transplants from people on a keto diet induced anxiety in mice, despite those people not reporting increased anxiety.Most assume if a diet improves human behavior (like reducing impulsivity), it must be mentally beneficial—but here, the same diet caused negative behavioral effects in animals via gut microbes.
- Keto diet increased brain levels of taurine, alanine, and betaine in mice—metabolites not typically linked to anxiety in prior human studies.These metabolites are usually associated with energy metabolism or liver function—not mood disorders. Their sudden link to anxiety via diet is a novel and unexpected pathway.
Practical takeaways
If you're struggling with depression and have obesity, try switching to a Mediterranean diet for 3 months—prioritize olive oil, vegetables, fish, and nuts.
This study had a small sample (only 23 completed Mediterranean participants) and high dropout rate—results aren’t definitive but are promising.
medium confidenceIf you're on keto for weight loss and notice increased irritability or anxiety, consider testing your gut health or adding fermented foods to balance your microbiome.
The anxiety link was only shown in mice—human anxiety wasn’t measured directly, so don’t panic, but stay curious.
low confidenceWhy this study matters
Mediterranean Diet Beats Keto for Depression
After three months, participants on the Mediterranean diet saw a 32% reduction in depressive symptoms, compared to just 14% for those on the ketogenic diet. This was measured using standardized depression scores in 23 completed Mediterranean participants versus 14 on keto.
Most people think low-carb diets like keto are better for mental health—but this study flips that idea, showing plant-rich eating may be the real mood booster.
Keto Reduced Impulsivity—But Made Mice Anxious
While the keto diet reduced urgency-related impulsivity (acting on sudden urges), fecal transplants from keto participants caused anxiety-like behaviors in mice. These mice showed elevated brain levels of taurine, alanine, and betaine—metabolites linked to mood disruption.
Your gut bacteria might be secretly controlling your emotions—even if you feel fine, your microbiome could be making others (or even your future self) anxious.
Gut Bacteria Are the Hidden Middleman
The study didn’t just observe diet effects—it proved causation by transplanting human gut microbes into mice. Keto diet microbes triggered anxiety in mice, while Mediterranean microbes didn’t, suggesting gut bacteria mediate diet-brain communication.
This isn’t just about food—it’s about the trillions of microbes inside you that talk to your brain. You’re not just what you eat—you’re what your gut bugs make from it.
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 tested two diets — one high-fat (keto) and one plant-based (Mediterranean) — on people with obesity to see how they affect mood and behavior, then tested the gut bacteria from these people in mice.
Research results
The Mediterranean diet made people 32% less depressed; keto made them 14% less depressed but reduced impulsive behavior. Mice given keto gut bacteria became anxious and had higher brain levels of taurine, alanine, and betaine.
What this means - more context
Yes — the difference in depression improvement (32% vs. 14%) is meaningful and suggests diet choice can strongly impact mood in obese adults.
This study investigates whether ketogenic and Mediterranean diets differentially affect depression and impulsivity in obese adults, with a focus on gut-brain axis mechanisms.
In a 3-month randomized trial, the Mediterranean diet improved depressive symptoms more than the ketogenic diet (32% vs. 14% reduction), while the ketogenic diet reduced urgency-related impulsivity. Fecal transplants from ketogenic diet participants induced anxiety-like behaviors in mice, linked to elevated brain taurine, alanine, and betaine, suggesting gut microbiota mediates diet-brain effects.
Methods Used
Sixty-four obese adults (BMI 30–45 kg/m², ages 18–65) were randomly assigned to either a ketogenic or Mediterranean diet for three months; 37 completed. Depression and impulsivity were measured pre- and post-intervention. Stool samples were analyzed for microbiota, and fecal transplants were performed in mice, followed by brain metabolite analysis via HR-MAS and 1H NMR spectroscopy.
Main Finding
The Mediterranean diet led to a 32% reduction in depression scores versus 14% with the ketogenic diet, while the ketogenic diet uniquely reduced urgency-related impulsivity; fecal transplants from ketogenic diet donors induced anxiety-like behaviors in mice with elevated brain taurine, alanine, and betaine.
Confidence Level
Moderate — randomized controlled trial with human and animal components, but small sample size (n=37 completers) and attrition limit generalizability.
Study Flags
Red Flags
- •Small sample size (n=37 completers)
- •High attrition rate (42%)
- •Animal findings not replicated in humans
Surprising Findings
Fecal transplants from people on a keto diet induced anxiety in mice, despite those people not reporting increased anxiety.
Most assume if a diet improves human behavior (like reducing impulsivity), it must be mentally beneficial—but here, the same diet caused negative behavioral effects in animals via gut microbes.
Practical Takeaways
If you're struggling with depression and have obesity, try switching to a Mediterranean diet for 3 months—prioritize olive oil, vegetables, fish, and nuts.
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 556 / 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 found that people who ate the Mediterranean diet felt less sad than those on the keto diet, but it wasn't a big or perfect test. It also gave mouse poop from people to mice and saw the mice got anxious — which is interesting, but doesn't prove the same thing happens in humans.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Randomized controlled design
- Use of validated outcome measures for depression and impulsivity
- Inclusion of mechanistic animal model (fecal transplant)
Weaknesses
- Unclear blinding status
- High attrition (27 participants dropped out)
- Uneven group sizes at completion (Med n=23, Keto n=14)
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists tested two diets — one high-fat (keto) and one plant-based (Mediterranean) — on people with obesity to see how they affect mood and behavior, then tested the gut bacteria from these people in mice.
Research results
The Mediterranean diet made people 32% less depressed; keto made them 14% less depressed but reduced impulsive behavior. Mice given keto gut bacteria became anxious and had higher brain levels of taurine, alanine, and betaine.
What this means - more context
Yes — the difference in depression improvement (32% vs. 14%) is meaningful and suggests diet choice can strongly impact mood in obese adults.
This study investigates whether ketogenic and Mediterranean diets differentially affect depression and impulsivity in obese adults, with a focus on gut-brain axis mechanisms.
In a 3-month randomized trial, the Mediterranean diet improved depressive symptoms more than the ketogenic diet (32% vs. 14% reduction), while the ketogenic diet reduced urgency-related impulsivity. Fecal transplants from ketogenic diet participants induced anxiety-like behaviors in mice, linked to elevated brain taurine, alanine, and betaine, suggesting gut microbiota mediates diet-brain effects.
Methods Used
Sixty-four obese adults (BMI 30–45 kg/m², ages 18–65) were randomly assigned to either a ketogenic or Mediterranean diet for three months; 37 completed. Depression and impulsivity were measured pre- and post-intervention. Stool samples were analyzed for microbiota, and fecal transplants were performed in mice, followed by brain metabolite analysis via HR-MAS and 1H NMR spectroscopy.
Main Finding
The Mediterranean diet led to a 32% reduction in depression scores versus 14% with the ketogenic diet, while the ketogenic diet uniquely reduced urgency-related impulsivity; fecal transplants from ketogenic diet donors induced anxiety-like behaviors in mice with elevated brain taurine, alanine, and betaine.
Confidence Level
Moderate — randomized controlled trial with human and animal components, but small sample size (n=37 completers) and attrition limit generalizability.
Study Flags
Red Flags
- •Small sample size (n=37 completers)
- •High attrition rate (42%)
- •Animal findings not replicated in humans
Surprising Findings
Fecal transplants from people on a keto diet induced anxiety in mice, despite those people not reporting increased anxiety.
Most assume if a diet improves human behavior (like reducing impulsivity), it must be mentally beneficial—but here, the same diet caused negative behavioral effects in animals via gut microbes.
Practical Takeaways
If you're struggling with depression and have obesity, try switching to a Mediterranean diet for 3 months—prioritize olive oil, vegetables, fish, and nuts.
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 556 / 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 found that people who ate the Mediterranean diet felt less sad than those on the keto diet, but it wasn't a big or perfect test. It also gave mouse poop from people to mice and saw the mice got anxious — which is interesting, but doesn't prove the same thing happens in humans.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Randomized controlled design
- Use of validated outcome measures for depression and impulsivity
- Inclusion of mechanistic animal model (fecal transplant)
Weaknesses
- Unclear blinding status
- High attrition (27 participants dropped out)
- Uneven group sizes at completion (Med n=23, Keto n=14)
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study tried to be fair by randomly assigning people to diets, which is good. But lots of people dropped out, and we don't know if they knew which diet they were on — so the results might be skewed. That means we can't fully trust it yet.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
63 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=64)+5.5/20
- Follow-up+10/10
100 / 100
54 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
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 556 / 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 supports causal inference, but blinding is unknown and attrition reduced sample size, which may introduce bias and limit confidence in causal claims.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding statements were disclosed in the provided text; study appears independently conducted.
The study lacks any declared funding sources or conflict of interest statement, which is a limitation for transparency. However, no evidence of industry influence, author affiliations with commercial entities, or funder involvement was found in the provided text.