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Short Summary
Main recommendation: Before starting fasting, expect and manage five common side effects: headaches or dizziness, bowel changes, sleep trouble, heartburn, and blood glucose shifts, with diabetics on glucose-lowering medication needing to consult a doctor first. Dr. Fung says most of these are temporary and can be eased with practical steps, and he shares Melissa's steady alternate-day fasting routine used for weight loss.
Key Points
- Headaches and dizziness are common early on and are thought to relate to lower salt intake; they usually fade after about two weeks.
- Bowel movements often slow during fasting simply because less is eaten, which is normal, while some people instead get watery stools as the body sheds water after insulin drops.
- Trouble sleeping can occur because fasting raises norepinephrine and energy levels, so the speaker advises not forcing sleep before you feel tired.
- Heartburn can occur as stomach acid rises into the esophagus and is expected to improve after weight loss.
- Blood glucose can drop, which is risky for people on diabetes medication, or rise slightly as stored glucose is released from the liver.
Details Worth Noting
- Concrete instructions:
- For headaches or dizziness: add more salt, either a pinch under the tongue or salt dissolved in water and drunk; if acceptable, bone broth with plenty of salt or sugar-free pickle juice.
- For constipation-like slowdown: if uncomfortable, use over-the-counter laxatives such as magnesium supplements (e.g., milk of magnesia) or psyllium husk, a fiber, mixed into a glass of water, allowed to soak briefly, then drunk.
- For watery stools or diarrhea: try psyllium husk, which soaks up water, and consider drinking less water while fasting; it often resolves within a few days.
- For sleep trouble: don't force sleep, go to bed only when tired, relax beforehand (meditation or reading a book instead of screens), consider blue light blockers, or take a bath with Epsom salts, which contain magnesium.
- For heartburn: add lemon juice to water or drink apple cider vinegar diluted in water, which the speaker says can stimulate stomach contraction; over-the-counter antacids are an option, and a doctor can advise on medication in severe cases; if it persists, shorten fasts or do shorter fasts more frequently.
- For blood glucose: talk to a doctor before any diet change, including fasting, especially if taking diabetes medication.
- Before fasting, try a low-carbohydrate diet, stick to the same diet without deviating, and fast consistently.
- Melissa's routine: alternate-day fasting of 36 to 42 hours, two or three times a week, e.g., dinner Monday, no eating Tuesday, first meal Wednesday.
- Hunger tip: hunger comes in waves and passes; keep busy with sparkling water, fasting podcasts, or articles.
- Overnight sleep during a 36-hour fast covers two sleeping periods, which the speaker says makes fasting feel almost free.
- Hunger is described as the number one worry for people starting fasting.
Bottom Line
Most early fasting side effects are temporary and manageable with salt, fiber, sleep habits, and acid adjustments, but anyone on diabetes medication should check with a doctor before starting.
