Similar to muscle memory, your body develops a "metabolic memory." Repeated periods of ketosis make your system more efficient at fat oxidation, allowing for quicker adaptation, fewer side effects, and greater benefits during subsequent ketogenic phases.

Ferriss points to the emerging field of metabolic psychiatry, where dietary intervention is used for severe mental illness. He cites cases where schizophrenia patients, after years of failed medications, get off all prescriptions by adopting a ketogenic diet. This approach stabilizes the brain by providing ketones as a clean energy source.

Ferriss notes significant physiological changes while in ketosis, including needing 2-3 fewer hours of sleep and at least doubling his breath-hold time. He also experiences a dramatic reduction in ruminative thoughts, improving mental clarity and sleep onset.

Beyond being an alternative fuel source, the ketone body beta-hydroxybutyrate (BHB) functions as a signaling molecule. It acts as an HDAC inhibitor, which can activate genes that enhance the body's antioxidant and cellular defense mechanisms, a pathway of interest in cancer therapy.

The anxiolytic effect of ketosis has a clear neurochemical basis. Elevated ketones increase the levels of the enzyme GAD (glutamic acid decarboxylase), which converts the brain's primary excitatory neurotransmitter, glutamate, into its primary inhibitory (calming) neurotransmitter, GABA, creating a more stable neurological state.

Baszucki finds he can directly influence his mood through diet. Being in ketosis induces a state of "calm optimism," making challenges feel solvable. Conversely, a glucose crash simulates minor depression, making problems seem untenable. This suggests a direct link between metabolic state and psychological outlook.

A moderate level of blood ketones, around 1.2 to 2 millimolars, can have an anxiolytic (anxiety-reducing) effect. However, spiking ketone levels significantly higher, often through large doses of exogenous supplements, can paradoxically increase anxiety and lead to a subsequent crash.

A key benefit of ketosis is its mood-enhancing effect. It doesn't suppress positive feelings but significantly reduces negative mood swings, making it a powerful tool for mental well-being and a primary reason for its adoption beyond weight loss.

Ketones are a more efficient energy source than glucose, producing less metabolic “trash” (oxidative stress). Crucially, they can penetrate the blood-brain barrier and fuel brain cells even when they've become resistant to insulin, directly combating cognitive decline and brain fog.