This randomized crossover trial examined whether carbohydrate restriction and exercise have additive effects on brain-derived neurotrophic factor (BDNF), a protein that supports learning, memory, and neuronal plasticity. Twelve adults with metabolic syndrome completed two four-week interventions: a carbohydrate-restricted Paleolithic diet alone and the same diet combined with high-intensity interval training (HIIT). Both interventions significantly increased circulating BDNF and improved measures of cognitive performance, with the combination of diet and exercise producing the greatest benefits.

Participants also experienced improvements in body composition, fasting glucose, triglycerides, and insulin sensitivity. Higher BDNF levels were associated with better metabolic health, suggesting that improvements in cognition and brain function may be linked to improvements in underlying metabolism rather than exercise or diet alone. While subjects spontaneously consumed fewer calories during the study, making it impossible to separate the effects of carbohydrate restriction from calorie restriction, the results are consistent with previous research showing that both dietary carbohydrate restriction and high-intensity exercise support brain health.

Taken together, these findings support the idea that diet and exercise produce complementary improvements in metabolic and cognitive health. Although the study was small and short in duration, it adds to evidence showing that restoring metabolic health through carbohydrate restriction and exercise may improve brain function alongside more traditional markers of metabolic disease.

https://pmc.ncbi.nlm.nih.gov/articles/PMC6822553/