Does a high-fat diet affect ADHD symptoms?

HFD and Dopaminergic Pathways

Let’s review a study by Kang et al., 2023 (citation at the bottom!). First things first – this was a mouse study. Now, mice studies are relatively generalizable to humans with ADHD, so that’s ok! However, like always, we want to interpret them with more caution than human studies.

With that out of the way, let’s review.

So the mice were split up into two groups: the control diet and the high-fat diet. They ate this diet consistently for two months.

For reference, the average American eats about 46% carbs, 16% protein, and 36% fats. When we consider the ketogenic diet (a diet initially created for seizure disorders, fun fact) this turns into ideally 70-75% fats, 20% proteins, and only 5-10% carbohydrates.

Following habituation to the diet, the researchers recorded EEGs during sleep and also did five validated tests to measure their cognitive abilities and hyperactivity tendencies.

Here’s what they found in the mice who were fed the HFD:

1. The REM sleep increased (possibly positive outcome if you don’t have ADHD…otherwise this is a negative outcome – Scarpelli et al., 2019)
2. They had decreased wakefulness during the day (negative outcome)
3. Increased anxiety behaviors during the open-field test (negative outcome)
4. Deficits in spatial memory during the acquisition trial and novel place recognition trial (negative outcome)
5. Increases in hyperactivity behaviors during the tail suspension test (negative outcome)
6. Decreases in the sucrose preference test (positive outcome)
7. Reduced brain dopaminergic system markers, specifically: significantly lower mRNA levels of DAT, COMT, and D1R gene (negative outcome)

So what should we take out of this? First, let’s recognize that this wasn’t done on mice in which we had already induced ADHD-like symptomology. Instead, the HFD was the thing that induced the ADHD symptoms and interrupted the dopaminergic pathways. However, if a high-fat diet can alter dopamine responses and pathways, it is highly likely that it can further impair the already dysregulated dopamine systems in people with ADHD. That being said, some research has indicated that a keto diet can improve ADHD symptoms.

So what’s actually true, Annika?

The answer? It’s the LENGTH that matters. What we see consistently is that more than five weeks of a high-fat diet can disrupt the system. Let’s think about this study – they had the mice on the diet for 8 weeks, and what did we see? Disruptions in mental health and neurotransmitter function.

TLDR; If you can manage it, eating a high fat diet for 3-4 weeks may be beneficial for your ADHD, though the research is still inconclusive. HOWEVER, long-term use of this diet may actually worsen symptoms. If you choose to go through with a high-fat diet, please consult a registered dietitian (US), nutritionist (UK), or your area’s trained nutrition professional.

Kang, J., Park, M., Oh, C., & Kim, T. (2023). High-fat diet-induced dopaminergic dysregulation induces REM sleep fragmentation and ADHD-like behaviors. Psychiatry Research, 327. https://doi.org/10.1016/j.psychres.2023.115412