The Science and Surprising Benefits of Prolonged Fasting

Modern research shows that medically supervised water-only fasting can reset key aspects of health. In one landmark study by Dr. Alan Goldhamer and colleagues, 174 patients with high blood pressure underwent ~10 days of water-only fasting (followed by careful refeeding).  By the end, most had normalized blood pressure without medications: the group’s average blood pressure fell 37/13 mmHg – roughly three times the effect of standard drugs .  In fact, 89% of these hypertensive patients reached normal blood pressure levels by the end of the fast/refeed, and all were able to stop their blood-pressure medications .  At follow-up, those who adopted a low-fat, whole-food diet after the fast largely maintained these gains.

This dramatic BP improvement came alongside healthy weight loss: the average patient lost about 8–9% of body weight during the ~3‑week program .  Notably, this was mostly body fat – TrueNorth reports suggest roughly 40% of that weight loss was visceral fat (the harmful belly fat linked to heart disease and diabetes).  (Lean muscle loss was minimal and typically rebounded on a normal diet.) In short, water-only fasting turned out to be vastly more effective than drugs in this setting – and without serious side effects.

Resting is crucial.  Doctors supervise fasts under strict clinical conditions.  Patients are told to rest almost completely during the fast – no strenuous exercise – because even moderate activity can greatly increase calorie burn and degrade muscle.  In Goldhamer’s study, therapists note that “even moderate activity during a water-only fast can double energy use,” so patients were limited to gentle activities (reading, meditating, light walking) .  This cautious approach minimizes dizziness and protects muscle.  (Indeed, clinicians report that hunger often subsides after a few days of fasting, and lean tissue losses fully recover with controlled refeeding.)

Refeeding is as important as fasting.  After the water fast, patients usually transition slowly back to food.  A common protocol is about one day of fresh vegetable/fruit juices for each week of fasting, followed by whole plant foods (fruits, vegetables, grains, legumes).  This gradual refeeding avoids dangerous electrolyte shifts.  In Goldhamer’s clinic, doctors monitor electrolytes and vital signs; if anything drops too low, they adjust calories or nutrients.  A mishandled refeed can cause “refeeding syndrome,” so medical guidance is key.  The payoff is that a proper refeed can reset your gut: by repopulating healthy microbiota, it helps regulate mood and hunger (remember ~90% of our serotonin/dopamine is made in the gut!).

How Fasting Works: Ketones, Autophagy and “Detox”

Why does this work?  Fasting triggers multiple beneficial switches in the body. After about 24 hours without food, liver glycogen is used up and the body switches to burning fat for energy.  This generates ketone bodies (like beta-hydroxybutyrate) that the brain and muscles can use.  This metabolic shift is a survival adaptation – it allowed our ancestors to endure famines and still think clearly.

One result is a natriuretic (water-shedding) effect.  When you stop eating salt, oil, and processed carbs completely, your body flushes out excess sodium and fluid.  Goldhamer points out that fasting “eliminates incoming sodium chloride,” causing a rapid loss of retained water and a drop in blood pressure .  In effect, a few days of salt-free fasting is like an ultra-powerful diuretic with no pills – and the BMI in the study confirms this diuresis (average BMI fell from 28.9 to 26.5) .

On a cellular level, fasting induces autophagy – a housekeeping process where cells break down old proteins and damaged components.  Autophagy literally “cleans up” the body’s tissues, clearing out waste and even pre-cancerous cells.  Animal studies show that regular fasting or calorie restriction can extend lifespan by 30–100% in rodents.  (By contrast, constant overeating often shortens life.)  This rejuvenation effect is one reason fasting can help conditions like arthritis, diabetes, and possibly some cancers – by giving cells a chance to regenerate free of metabolic trash.

Fasting also mimics some benefits of exercise.  For example, it can boost brain-derived neurotrophic factor (BDNF), a protein that supports brain health and memory (BDNF rises during exercise and may also increase during fasting).  While research is ongoing, higher ketones may promote BDNF release, helping to protect against neurodegeneration.  In short, fasting engages the brain and body’s built-in repair programs.

Beyond Blood Pressure: Other Therapeutic Effects

Water fasting has shown promise in many other areas.  In a recent randomized trial, a 10-day fasting regimen (under 500 kcal/day) dramatically improved menstrual pain in young women with primary dysmenorrhea.  Participants on the fast reported far less cramping, nausea, vomiting and dizziness during their periods, along with better quality of life scores – and these benefits lasted for several months after the fast .  This suggests that fasting can reset inflammatory or hormonal patterns causing menstrual pain.

There are also encouraging case reports in cancer and fertility.  Goldhamer co-authored a published case of a 42-year-old woman with follicular lymphoma (a type of slow-growing blood cancer).  She underwent a 21-day water-only fast followed by a plant-based diet (no sugar, oil, or salt) .  Remarkably, her cancer went into remission: enlarged lymph nodes shrank and became non-palpable.  At 6- and 9-month checkups she remained asymptomatic.  (Subsequent reports suggest she stayed cancer-free for years afterward.)  While one case doesn’t prove a cure, it aligns with lab studies showing fasting can sensitize cancer cells to treatment and eliminate damaged cells.

Anecdotally, Goldhamer notes that women with conditions like PCOS or irregular cycles often see improvements after therapeutic fasting.  Some report that their cycles normalize instead of shutting down, and couples struggling with infertility have sometimes conceived following a dietary “reset.”  The theory is that by lowering excess insulin and inflammation through fasting, hormone balance can improve.

Even relatively healthy people notice benefits.  After a multi-day fast, many report sharper mental clarity, reduced sugar cravings, and a permanent recalibration of their taste buds (healthy whole foods taste better).  In the clinical experience of TrueNorth Health, even brief fasts of 3–7 days can help “reboot” metabolism.  Therefore, Goldhamer and others often recommend that most individuals fast once or twice a year for a week or so, on top of a daily ~12‑hour overnight fast. This gives the body a periodic reset without extreme sacrifice.

The Modern Diet vs. Fasting

Today’s standard diet – high in salt, sugar and processed oils – works against the body’s natural signals.  These ingredients are hyper-palatable: they overstimulate the brain’s reward centers and promote overeating.  In Goldhamer’s words, modern junk foods act like “magical poisons” that hijack our dopamine pathways .  By contrast, after a fast, foods like plain fruit or whole grains taste intensely satisfying because your palate has been reset.

This contrast helps explain why the so-called “diseases of affluence” (obesity, diabetes, hypertension, heart disease, etc.) are now epidemic.  In the past, these were “diseases of kings” who overate rich foods.  Now roughly three-quarters of people in industrialized countries are overweight or obese, and visceral fat–related illnesses are rampant.  Fasting directly targets that excess: by shutting off the food pump and forcing the body to use stored fat (especially visceral fat), fasting removes a root cause of chronic inflammation.

Safety and Common Myths

Many readers worry: won’t fasting make me weak or waste muscle?  Actually, evidence suggests the opposite.  In the TrueNorth hypertension study, patients reportedly did not find the fast unbearable.  After the first couple of days, hunger subsided and they had stable energy during rest .  Lean muscle loss was modest (BMI barely budged after refeeding) , and muscle quickly recovered with a normal diet.  Nutritionists emphasize “therapeutic fasting” should always be done with medical oversight – to provide vitamins/minerals if needed and to monitor vital signs.

Another myth is that all the lost weight will come back immediately.  In reality, many people maintain a lower body weight after learning new habits post-fast.  Fasting seems to reduce leptin resistance and improve insulin sensitivity, meaning the body doesn’t go into a starvation rebound as easily.  True, if one returns to pizza-and-soda habits, weight will return.  But the fasting experience often changes behavior: patients report a lifelong preference for whole foods over junk.

Finally, some worry fasting could induce nutrient deficiencies or weaken the immune system.  In contrast, data show that short-term water fasts boost immune function.  One lab study found fasting cycles can regenerate the hematopoietic (blood cell) system and rejuvenate immune cells.  And clinically, Goldhamer notes that many fasting patients report feeling “reset” afterward – with reduced joint pain, allergies or asthma symptoms, as if their immune system was recalibrated.

Getting Started and Next Steps

If you’re curious, the simplest thing is to try a short fast at home: extend your overnight fast to 14–16 hours (e.g. eat dinner by 7pm and skip breakfast).  Drink water (and herbal teas if you like) and spend that extra morning time on gentle activity or meditation.  You’ll tap into some fat-burning and give your digestion a break.  Even this daily 16-hour fast has been shown to improve metabolism.

For more ambitious fasting (several days and beyond), medical guidance is wise.  Fasting clinics like TrueNorth Health Center supervise water-only fasts up to 40 days, (I know, I was pretty shocked when I first heard about this) with daily exams and lab tests.  They typically prepare patients with a raw vegan diet beforehand and refeed them slowly afterward, as described earlier.  While a 40-day fast sounds extreme, less than 1% of people ever fast that long; most clinic patients do 10–28 days, depending on their condition.

Personally, I have done a 5-day water only fast. And I am very, very impressed by the results. I am an adult male, ~78KG, 19% body fat before start of the fast. I lost 3KG in those 5-days. I did binge eat in my first attempt (a poor one at that!) back in the 6th and 7th day and gained some weight back, but I have noticed the benefits carried forward to the following 2 weeks. The 1st week I was back up to 78 KG and 18% body fat, but the 2nd week, while continuing the same normal diet, I am maintaining at 76KG and 16% body fat. I am in a continuous experiment to see when will be my next fast, but I can assure you - it works. The mental alacrity that follows cannot be understated - you will gain so much more than the emotional hunger that comes with prolonged, water-only fasting.

In summary: fasting is a powerful metabolic therapy.  It taps into ancient survival mechanisms to reduce fat, lower insulin and blood pressure, and clean up body systems – all without drugs.  The science is still evolving, but decades of work by Goldhamer and others show that “doing nothing” (just water and rest) can sometimes be the most effective medicine.  Of course, fasting isn’t a magic bullet – it works best when combined with a nutritious diet, exercise, and other healthy habits.  But for anyone skeptical, it’s hard to ignore the data: after a well-supervised fast, patients often marvel that something so simple could be so transformative .

Sources: DOAC - World No.1 Fasting Expert: The Link Between Cancer & Fasting That They're Hiding From You!