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.

Adding Medium-Chain Triglyceride (MCT) oil to exogenous ketone supplements (like BHB salts or esters) leads to a higher and more prolonged elevation of blood ketone levels than taking either substance alone. The MCT oil slows the absorption of the supplemental ketones, extending their effect.

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.

A common ingredient in ketone esters, 1,3-butanediol, is metabolized like alcohol and can be toxic with chronic use. It can deplete the liver's NAD and ATP stores, potentially causing inflammation, fatty liver, and other adverse effects.

Long-term, consistent use of ketone esters based on 1,3-butanediol, a very common formulation, may lead to liver toxicity. This risk exists even at doses that are not considered excessively high, such as those used by endurance athletes or in protocols for Alzheimer's.

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.

The ketogenic diet has a profound neuropharmacological effect, acting as a brain stabilizer. It reduces levels of the excitatory neurotransmitter glutamate while increasing the main inhibitory neurotransmitter, GABA. This quieting effect explains its efficacy in treating epilepsy and anxiety.

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.

While many aim for the highest possible ketone readings, research indicates the therapeutic 'sweet spot' is 1-2 millimolar for most applications. Levels above this can cause 'reductive stress' and energy toxicity, which are counterproductive for general metabolic health.