Question 1

What physiological changes happen at 12, 16, and 24 hours of fasting?

Accepted Answer

At 12 hours, glycogen stores begin depleting and the body transitions to fat oxidation, with ketone levels starting to rise. At 16 hours, autophagy (cellular self-cleaning) is significantly upregulated, growth hormone surges 300-500%, and insulin reaches its lowest baseline. At 24 hours, autophagy peaks, the body achieves deep ketosis (0.5-2.0 mmol/L BHB), and significant cellular repair pathways like AMPK and sirtuins are fully activated.

Question 2

Is intermittent fasting safe and does it cause muscle loss?

Accepted Answer

Intermittent fasting (16:8 or 18:6) is generally safe for healthy adults. Research shows that fasting up to 24 hours does not significantly increase muscle protein breakdown when adequate protein is consumed during eating windows (1.6-2.2g/kg/day). The growth hormone surge during fasting actually helps preserve lean mass. However, extended fasts beyond 48 hours without medical supervision may risk muscle catabolism.

Question 3

What should I eat to break a fast to avoid blood sugar spikes and refeeding issues?

Accepted Answer

After a 16+ hour fast, break your fast with easily digestible, low-glycemic foods. Start with bone broth or a small amount of healthy fats (avocado, MCT oil) to gently reactivate the digestive system. Follow with protein (eggs, fish) after 15-20 minutes. Avoid high-sugar foods, refined carbs, and large portions which can cause reactive hypoglycemia and insulin spikes. For fasts over 24 hours, a 30-minute refeeding protocol is recommended.

间歇性禁食追踪器

AI 间歇性断食追踪 | 自噬阶段与昼夜节律同步

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