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.

When training for a mental sport like chess, the foundational step is stabilizing energy by managing glucose metabolism, perhaps via intermittent fasting. Many athletes jump to "smart drugs" and stimulants, but this is ineffective if the underlying energy system is volatile and prone to crashes.

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.

Contrary to popular belief, fasting for up to four days actually increases your basal metabolic rate. Instead of shutting down to conserve energy, your body activates a hormonal 'fight-or-flight' response that increases energy expenditure to help you find food.

While short-term keto adaptation (first month) may show no power gains, long-term adaptation (6-18 months) trains muscles to efficiently use fat as fuel. This results in significant power increases, with studies on soldiers showing up to a 50% improvement over their non-keto counterparts.

After becoming fat-adapted on a ketogenic diet, strategically inserting 1-2 days of high-protein, low-fat meals (e.g., lean protein and vegetables) can rapidly increase fat mobilization from your body's stores, leading to accelerated fat loss.

Unlike simple calorie restriction, intermittent fasting lowers insulin levels. This hormonal signal allows your body to access and burn its fat stores to make up for a caloric deficit, preventing the metabolic slowdown that typically sabotages diets.

Low measured ketone levels on a strict ketogenic diet may not be a failure. It can signify high metabolic fitness, where your body is so efficient at utilizing ketones for energy that fewer are left circulating in the blood to be measured, creating a false negative.

A major pitfall of intermittent fasting is the loss of lean muscle tissue. To counteract this, it must be combined with dedicated resistance training. This combination allows for the metabolic benefits of fasting while signaling the body to retain and even build muscle, which can be tracked through strength gains.