digest
Short Summary
Main recommendation: Start intermittent fasting by first recognizing that you already fast during sleep, then gradually extend that overnight fast by about 30 minutes to an hour at a time, working toward a continuous fasting window of at least 12 hours and eventually 16 to 18 hours. Dr. Berry says this approach may improve blood sugar, insulin levels, and weight, and notes it costs nothing to do.
Key Points
- The fasting window is the stretch of time when you avoid carbohydrates and protein, while the feeding window is when you eat; the fast should be one continuous block rather than broken up.
- Dr. Berry says fasting is not starvation but extending the fasting period you already do each night, and he compares it to the eating patterns of ancestors.
- He reports that some patients with diabetes were able to come off medications, including insulin, and that this led to further weight loss; these are his patients' reported results, not a study.
- He argues that intermittent fasting is free and unmarketable, which he speculates is why large companies and health organizations do not promote it.
- He claims the idea that you must eat every two hours to keep energy up is a myth promoted by companies that profit from frequent eating, though he offers no evidence for this.
Details Worth Noting
- Concrete instructions:
- Week 1 to 2: If you normally sleep 8 hours, extend your overnight fast to about 9 hours by skipping breakfast or pushing your first meal later, then keep that schedule for one to two weeks until it feels comfortable.
- Morning rule: After waking, avoid carbohydrates and protein. Coffee or tea is allowed, but without sweetener; you may add a good-quality fat instead, since that will not raise insulin and break the fast.
- Progression: Once comfortable, add another 30 minutes to an hour to the fast, and repeat the adjustment for a week or two before adding more.
- Target: Aim for a continuous fast of at least 12 hours, which you reach by adding four to five hours to your sleep fast.
- Advanced target: Dr. Berry personally fasts 16 to 18 hours a day.
- Eating window: Ideally eat a healthy diet during the feeding window, but he says continuing your current diet is possible if healthy food is not affordable.
- Do not start with a 16-hour or two-day fast, which he considers too aggressive at the beginning.
- He says the fast can be done anywhere, at no cost, and that he sees no need to buy any product to do it.
- Dr. Berry says the common advice to keep diabetics' blood sugar between 120 and 200 is poor, and he personally recommends keeping it below 120 when possible, since he says high levels can cause permanent cell damage.
- He notes that anyone with diabetes on medication should be aware that fasting can lower blood sugar, which is why he describes medication reduction as a result patients reached with their doctors; he does not provide specific medication-adjustment instructions.
- He says hunger is typically absent during the fast once the body adapts, though this is his personal experience.
Bottom Line
Intermittent fasting, as Dr. Berry describes it, is a gradual, free way to lengthen the overnight fast you already do, and his guidance centers on building up slowly from your current sleep schedule rather than starting with extreme fasts.
