The pre-specified whole-cohort analysis did not demonstrate statistically significant or clinically meaningful changes in psychological well-being or kynurenine metabolites following a 12-week combined TRE and endurance exercise intervention, though exploratory post hoc analyses suggest changes in psychological well-being and peripheral kynurenine metabolism may co-occur.
Key Findings
Results
The pre-specified analysis of the entire cohort did not reveal statistically significant or clinically meaningful changes in psychological well-being, kynurenine metabolites, or inflammatory biomarkers.
Seventy-one healthy adults participated in the 12-week intervention.
Assessments included the State-Trait Anxiety Inventory, Mood Adjective Checklist, body composition, inflammatory markers, and serum kynurenine profiling.
The intervention combined a 12-week endurance training program with a 10-hour time-restricted eating window.
Assessments were conducted at baseline and post-intervention.
Results
Both older (OE-TRE) and younger (YE-TRE) age-stratified groups showed significantly lower body mass and BMI following the intervention.
Participants were stratified into older (OE-TRE) and younger (YE-TRE) groups in exploratory post hoc analyses.
Both groups showed significantly lower body mass and BMI at the second measurement.
These analyses were conducted post hoc and should be considered exploratory.
Age-based stratification was not a pre-specified analysis.
Results
Serum anthranilic acid (AA) levels changed in opposite directions between the older and younger groups following the intervention.
In the OE-TRE group, serum anthranilic acid (AA) levels increased (Δ = +7.85 nmol/L).
In the YE-TRE group, serum anthranilic acid (AA) levels decreased (Δ = -2.62 nmol/L).
These findings are from exploratory post hoc analyses stratified by age.
These findings are described as associative and hypothesis-generating and do not establish an intervention effect or causality.
Results
Among participants with complete psychological data, 66.7% showed lower anxiety scores at the second measurement, and this anxiety-defined subgroup also showed lower serum 3-hydroxykynurenine (3-HK) concentrations.
Participants were stratified according to the direction of change in anxiety scores in a separate exploratory post hoc analysis.
66.7% of participants in this subgroup showed lower anxiety scores at the second measurement.
The anxiety-defined subgroup showing lower anxiety also showed lower serum 3-HK concentrations.
This observation was confined to the exploratory subgroup analysis and should not be interpreted as a general reduction in 3-HK in the study cohort.
The decrease in 3-HK was not observed in the study cohort as a whole.
Results
The OE-TRE group showed an increase in the xanthurenic acid (XANA) + picolinic acid (PA) to 3-HK ratio and a reduction in TNF-α.
The XANA + PA to 3-HK ratio increased in the older exercise-TRE group.
TNF-α was reduced in the OE-TRE group.
Differences between age groups in the 3-hydroxyanthranilic acid (3-HAA)/3-HK and XANA + PA/3-HK ratios that were observed at baseline were no longer present at the second measurement.
These findings are from exploratory post hoc analyses and should be considered hypothesis-generating.
Results
In the exploratory subgroup of participants whose 3-HAA concentrations increased over time, soluble gp130 (sgp130) concentrations were lower at the second measurement.
This finding was identified through exploratory subgroup analysis.
sgp130 is a soluble form of the IL-6 signal transducer glycoprotein 130.
The analysis is described as associative and hypothesis-generating.
This finding does not establish an intervention effect or causality.
What This Means
This research suggests that combining a 12-week endurance exercise program with a 10-hour daily eating window (time-restricted eating, or TRE) did not produce statistically significant or clinically meaningful improvements in mood, anxiety, or biochemical markers related to tryptophan metabolism when the full group of 71 healthy adults was analyzed together. Tryptophan metabolism produces various compounds in the body, including kynurenine metabolites, some of which have been linked to mood and mental health. The researchers specifically wanted to know whether psychological changes would coincide with changes in these metabolites, but the primary analysis found no clear pattern across the whole group.
When the researchers conducted additional exploratory analyses — dividing participants by age or by whether their anxiety scores went up or down — some interesting patterns emerged. Both older and younger participants lost body weight and reduced BMI. Older participants showed different patterns of anthranilic acid changes compared to younger participants. Among those whose anxiety scores decreased (about two-thirds of participants with complete data), lower levels of a potentially neurotoxic metabolite called 3-hydroxykynurenine (3-HK) were also observed. The older group also showed reductions in the inflammatory marker TNF-α. However, the researchers emphasize that these secondary findings were not planned in advance, involve smaller subgroups, and should be considered hypothesis-generating rather than definitive conclusions.
This research suggests that age and individual psychological response patterns may influence how the body's tryptophan metabolism responds to combined exercise and dietary timing interventions. The findings are described as associative, meaning the study cannot determine whether the exercise-TRE program caused these changes or whether other factors were responsible. Future studies with pre-planned subgroup analyses and larger sample sizes would be needed to confirm or refute these exploratory observations.
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Juhas U, Budnik-Przybylska D, Borkowska A, Kortas J, Reczkowicz J, Ziemann E, et al.. (2026). Changes in Mood and Tryptophan Metabolism Following a 12-Week Endurance Exercise Combined with Time-Restricted Eating in Healthy Adults.. Nutrients. https://doi.org/10.3390/nu18193116