As we age, the timing of calorie consumption becomes more critical than the quantity. One calorie consumed after 6 PM can have the metabolic impact of ten calories consumed before noon due to its effect on insulin production during sleep. This highlights the importance of front-loading caloric intake.

Forget complex sleep metrics; the single highest-value biomarker to track for sleep quality is your resting heart rate just before bed. Actions that lower it (e.g., early final meal, no screens) are beneficial, while those that raise it are detrimental. It provides a simple, actionable daily target.

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.

To successfully change your lifestyle, tackle habits in a specific order. First, master sleep to increase your baseline willpower. Use that newfound energy to establish a consistent exercise routine. Only after those two pillars are in place should you address the emotionally complex challenge of diet.

Bryan Johnson suggests focusing on a single metric: pre-sleep resting heart rate. Lowering it through specific habits (like eating 4 hours before bed) improves sleep quality, which in turn boosts your prefrontal cortex, enhancing willpower and alleviating mental health issues.

Even when total calories are held constant, compressing your eating window (e.g., fasting for 18 hours) provides metabolic benefits that simple calorie restriction does not. Studies show this approach leads to superior improvements in glucose regulation and blood pressure control.

Contrary to popular low-carb diet advice, consuming starchy carbohydrates in the evening can significantly improve sleep quality. Carbs help lower cortisol, the body's stress hormone, which needs to be low at night for restorative sleep. This explains why many low-carb dieters struggle with sleep disruption.

Time-restricted eating (fasting for 12-14 hours) is crucial for gut health. This rest period allows a specific group of microbes to emerge and perform essential maintenance, cleaning and repairing the gut lining to prevent inflammation.

Consuming sugary foods before bed leads to high blood glucose, which activates the sympathetic nervous system (fight or flight). This physiological stress state increases heart rate and body temperature, directly opposing the calm, parasympathetic state required for restorative sleep and leading to poor sleep quality.