Shifting to a low-carbohydrate diet increases baseline cortisol because the body needs to mobilize energy stores more actively. This can lead to feelings of being "wired but tired" and can disrupt sleep, especially during the adaptation period.
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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.
Instead of medicating or ignoring symptoms like fatigue or mood swings, view them as your body's way of signaling an underlying issue. By treating symptoms as messages, you can focus on the root cause (like glucose spikes), which makes the 'messages' disappear.
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.
When addressing hormone imbalances, start at the base of the "hormone pyramid." Optimizing foundational hormones like cortisol (stress) and insulin (blood sugar) is essential, as they directly impact thyroid function and sex hormones like estrogen and testosterone.
Eating high-carb foods frequently, even in a calorie deficit, keeps insulin high. This prevents your body from accessing stored fat for energy, forcing it to lower its metabolic rate. After the diet, this suppressed metabolism causes rapid weight regain.
Cortisol isn't just a negative stress hormone. The "cortisol awakening response" is a natural, healthy spike that provides the energy and alertness needed to start your day. Optimizing this spike is crucial for setting your entire daily rhythm.
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.
The time required to enter ketosis varies dramatically. A healthy person might take a few days, but someone with years of high insulin resistance could need over two weeks of strict low-carb dieting to deplete their massive glycogen stores and begin producing ketones. This manages expectations and prevents premature failure.
Failing to achieve a high cortisol peak in the morning results in a "flattened" cortisol curve. This makes your system over-reactive to stress later in the day, leading to larger, more lasting cortisol spikes that disrupt sleep and cause anxiety.