How Running Counters Junk-Food Damage to Mood & Brain Health

By Matt • Updated October 2025

New research from University College Cork shows that voluntary running can reverse many of the mood-damaging and hormonal effects produced by a Western-style “cafeteria” diet — even when the unhealthy diet continues. This work sheds light on how exercise, gut metabolites, and hormones interact to support mental wellbeing.

Quick summary of the study

Researchers fed adult male rats either standard chow or a rotating “cafeteria” diet made up of high-fat, high-sugar foods for about seven and a half weeks. Some rats in each diet group had access to running wheels, allowing the team to compare diet vs. diet+exercise effects. The study found that running:

Produced antidepressant-like behavioral effects, even in rats on the junk-food cafeteria diet.
Restored several gut metabolites (anserine, indole-3-carboxylate, deoxyinosine) that were reduced by the unhealthy diet.
Normalized elevated insulin and leptin levels seen in sedentary rats fed the cafeteria diet — suggesting exercise rebalances key metabolic hormones.
However, the cafeteria diet blocked the usual exercise-induced increase in hippocampal neurogenesis — indicating diet quality still matters for full cellular benefits of exercise.

Why this matters for mental health and lifestyle

This study helps explain two things many of us observe in daily life: (1) exercise improves mood, and (2) poor diet can blunt some brain benefits. The metabolomic and hormonal findings suggest exercise restores certain gut metabolites and hormone balances that support emotional resilience — even when diet is suboptimal. But for the deepest brain-level benefits (like new neuron formation in the hippocampus), diet quality still plays a crucial role.

Key takeaways

Exercise is powerful: Running provided antidepressant-like effects despite the junk-food diet.
Gut-brain links matter: Specific gut metabolites changed with both diet and exercise — reinforcing the microbiota-gut-brain axis as central to mood regulation.
Diet still counts: A poor diet limited exercise’s ability to increase hippocampal neurogenesis — so you get bigger wins when you combine better nutrition with movement.

Practical advice — what you can do today

Whether you follow a plant-forward lifestyle or you’re simply trying to improve mood and resilience, these practical steps translate the study into everyday action:

Move consistently: Aim for regular aerobic activity you enjoy — walking, jogging/running, cycling, or swimming. Even voluntary daily movement matters.
Prioritize whole foods: Reduce ultra-processed “cafeteria” style foods and increase whole, plant foods — fruits, vegetables, whole grains, beans, nuts, and seeds — to support gut metabolites and brain health.
Pair diet + exercise: For maximal brain plasticity and mood benefit, combine consistent exercise with improved diet quality. Exercise helps even when diet slips, but the full benefit is synergistic.
Small steps add up: If you’re changing both diet and exercise, start with manageable habits — a 20–30 minute brisk walk plus one extra serving of vegetables each day is a meaningful start.

How this aligns with a plant-based approach

At PlantifulLife, we promote whole-food, plant-based choices because they improve metabolism, provide prebiotic fiber for gut microbes, and support hormonal balance — all factors implicated in the study’s mechanisms. Choosing minimally processed plant foods makes it easier for exercise to deliver its full brain benefits. Consider recipes rich in fiber and polyphenols (berries, greens, legumes) that feed beneficial gut metabolites and complement your movement routine.

Limitations & context

Important context: the study used male rats, so translation to humans — and to women — requires caution and further research. The intervention length (≈7.5 weeks) also may not capture long-term adaptations. Nonetheless, the mechanistic insights into metabolites and hormones provide a strong rationale for lifestyle strategies combining movement and healthy eating.

Final thought

Good news: even if your diet isn’t perfect, regular exercise — like running or brisk walking — can protect mood and metabolic balance. Better yet: combine movement with a plant-centred diet and you stack the odds in favor of long-term brain health and resilience. For resources, meal plans, and workout guides that fit real life, check out PlantifulLife.