Effects of a Ketogenic Diet Intervention on Affective Valence in Masters-Level Athlete: A Case Study

The ketogenic diet (KD) has been promoted as a quick way to lose weight and has gained international popularity over the last decade.With this rise in popularity has come an increase in research.Much of the research on KDs has focused on the diet as a primary or adjuvant therapy for neurological disorders, as it was originally developed for children with intractable epilepsy (Wheless, 2008).More recently, research has been done on exercisers and athletes from various backgrounds.The results are mixed, and the literature lacks studies directly assessing changes in affective valence inathletes.Additionally, there is a suggestion that the KD harms bone health (Heikura et al., 2020), but no research has been done with runners.The current study fills a research gap by examining both affect and bone health changes due to a KD.A KD involves a rather unconventional macronutrient profile by modern standards.In a typical 2,000 kcal/day KD, 70% of the total calories come from fats, 20% from proteins, and 10% from carbohydrates.In clinical applications to control epilepsy, fat is kept near 90% and protein is capped at 1 g/kg/day, with carbohydrates consistently held between 20 and 50 grams per day (Meira et al., 2019).When carbohydrates are kept low or prolonged fasting/starvation occurs, a series of biological and chemical changes take place to adjust for the lack of glucose availability.As a result of the carbohydrate reduction, there is an upregulation of the fatty acid oxidation pathways, a downregulation of glycolytic pathways, and increased reliance on hepatic gluconeogenesis.The body must then rely on fat as the primary fuel source, leading to increased -oxidation in the liver, which produces Acetyl-CoA to generate ATP.Many effects of KDs are neurological and psychological.As noted earlier, the KD was developedfor intractable epilepsy, but more work is being done on other diseases.AKD has helped patients with Parkinson's and Alzheimer's by reducing motor symptoms and improving memory and cognition (Lange et al., 2017;Phillips et al., 2018).The underlying mechanisms are poorly understood but may be linked to improved mitochondrial efficiency and decreased glycolytic flux (Wodarek, 2019).When KDs are tested in individuals with major depressive disorder, the KD appears to improve symptoms and mood (Wodarczyk et al., 2021).KDs seem to be positively correlated with increases in the inhibitory neurotransmitter gamma aminobutyric acid (GABA), and potentially the regulation of circulating glutamate, creating a more favorable GABA:glutamate ratio (Yudkoff et al., 2007).Low