Is Fasting for Weight Loss Safe?


[Music] although fasting for a week or two can actually interfere with the loss of body fat eventually after the third week of fasting fat loss starts to overtake the loss of lean body mass in obese individuals but is it safe to go that long without food proponents speak of fasting as a cleansing process but some of what you’re purging from your body or essential vitamins and minerals heavy enough people can go up to 382 days without calories but no one can go even a fraction of that long without vitamins scurvy for example it’s diagnoseable with as few as four weeks without any vitamin C berry berry and thymine are vitamin b1 deficiency let me start out even earlier in fasting patients and once manifests can result in brain damage within days which can eventually become irreversible even though fasting patients report problems such as nausea and indigestion taking supplements all the months long fasting cases I’ve mentioned in the last few videos were given daily multivitamins in mineral supplementation as necessary without supplementation hunger strikers and those undergoing long fasts for therapeutic or religious purposes like the Baptist pastor hoping to enhance his spiritual powers for exorcism have ended up paralyzed comatose or worse nutrient deficiencies aren’t the only risk reading about all that successful reports of massive weight loss from prolonged fasting in the medical literature one doctor decided to give it a try with his patients of the first dozen he tried it on though two died now in retrospect both of the two patients that died started out with heart failure and were on diuretics fasting itself produces a pronounced diuresis meaning loss of water and electrolytes through the urine so was the combination of fasting on top of the water pills that likely depleted their potassium and triggered their fatal heart rhythms the doctor went out of his way to point out that both of those who died started out in severe heart failure and both had improved greatly while undergoing starvation therapy small consolation since they were both dead within a matter of weeks not all therapeutic fasting fatalities were complicated by concurrent medication use at first he did very well and experienced the usual euphoria his electrolytes remained fine but in the middle of the third week he suddenly collapsed and died this line of treatment is certainly tempting because it does produce weight loss and the patient feels so much better but the whole killing people thing must make it a very suspect line of management contrary to the popular notion that the heart muscle is specially spared during fasting the heart appears to experience similar muscle wasting this was noted in the victims of the Warsaw Ghetto during World War two in a remarkable series of detailed studies carried out by the ghetto physicians themselves before they themselves succumbed in a case entitled gross fragmentation of cardiac fiber after therapeutic starvation for obesity a 20 year old woman successfully achieved her ideal body weight after losing 128 pounds fasting for 30 weeks after a breakfast of one egg she had a heart attack and died on autopsy the muscle fibers in her heart showed evidence of widespread disintegration the pathologist suggested that fasting regimens should no longer be recommended as a safe means of weight reduction breaking the fast appears to be the most dangerous part after World War two as many as one out of five starved Japanese prisoners of war tragically died following liberation now known as refeeding syndrome multi-organ system failure can result from resuming a regular diet too quickly see there are critical nutrients such as thymine and phosphorous that are used to metabolize food so in the critical refeeding window if too much food is taken before these nutrients can be replenished demand makes seed supply and whatever residual stores you still carry can be driven down even further with potentially fatal consequences that’s why rescue workers are taught to always give Thiemann before food to victims who had been trapped or otherwise unable to eat thymine is responsible for the yellow color of banana bags a term you might have heard used on medical dramas used to describe an IV fluid concoction often given to malnourished alcoholics to prevent a similar reaction anyone with negligible food intake for more than five days may be a risk for developing refeeding problems medically supervised fasting has gotten much safer now that there are proper refeeding protocols we know what warning signs to look for and we now know who shouldn’t be fasting in the first place such as those with advanced liver kidney failure porphyria uncontrolled hyperthyroidism and pregnant and breastfeeding women the most comprehensive safety analysis of medically supervised water only fasting was recently published out of the True North health center in California out of 768 visits to their facility for fasts up to 41 days were there any adverse events yes 5960 one of them but most were mild known reactions to fasting such as fatigue nausea insomnia headache dizziness upset stomach back pain they report only two serious events and no fatalities fasting longer than 24 hours and particularly three or more days should only be done under the supervision of a physician and preferably in a live-in clinic in other words don’t try this at home this is not just a legalistic mumbo-jumbo for example normally your kidneys dive into sodium conservation mode during fasting but should that response break down you could rapidly develop an electrolyte abnormalities that may only manifest with nonspecific symptoms like fatigue or does which could easily be dismissed until it’s too late the risks of any therapy must be premise Thanh the severity of the disease I mean the consequences of obesity are considered so serious that effective therapies could have considerable acceptable toxicity for example many consider major surgery for obesity to be a justifiable risk but the key word is effective therapeutic fasting for obesity has been largely abandoned by the medical community not only because of its uncertain safety profile but it’s questionable short-term and long-term efficacy remember for a fast that only lasts a week or two you might be able to lose as much body fat or even more on a low-calorie diet than a no calorie diet [Music] you

63 thoughts on “Is Fasting for Weight Loss Safe?

  1. losing weight too fast can trigger a gall bladder attack. then you'll have to go to the ER and get it cut out of you.

  2. I have lost over 115lbs fasting. My first fast was 25 days. Therapeutic starvation is a term that shows me you weren’t fasting. Breaking the fast is extremely important. Starvation is not fasting. I’ve dove 3 other extended fast from 17-24 days. I’m a leader in a fasting community that can give you guys a real look into fasting. Here is my fasting interview with over 77,000 views. Do true research. https://youtu.be/ArC0xfjEghI You can try it at home. Lol Know what your body is going through and ask those who actually fast and have had success. Doctors won’t promote anything that will get you off of medications and reverse cancer and diabetes. Someone who hasn’t done an extended isn’t the one to help you. A healthy alternative YouTube channel and fasting page with the leader Chris James will share valuable information. There are plenty of success stories including mines. Fasting saved my life in many ways.

  3. Because throughout our million years of evolution we always had plenty of fruits and vegetables, sourced from all around the world, all through the year, and were always eating 3 meals a day with snacks in between. Periods without food? Danger!
    Give me a break.

  4. Why are your findings in complete opposition to virtually all current studies on fasting? The current medical literature conclusively demonstrates that fasting does not result in loss of muscle mass, that blood profiles remain in normal ranges, that HGH is substantially elevated and that the resultant autophagy is beneficial to disease management and prevention. No mention was made of blood sugar normalization. Studies of terminally ill obese patients from 50 years ago or WWII prisoners are not applicable to healthy individuals, and you know it or should know it. You intentionally fail to distinguish between fasting and starvation, and state that refeeding syndrome applies to the former when it clearly does not. If you are not going to cite the most current literature demonstrating the safety and efficacy of fasting, you should stick to promoting salads. This is an agenda-driven, not fact-driven series of videos.

  5. I know several guys on an unhealthy diet, who try to compensate with 1 week of fasting, especially before important events. A whole food plant based 🍅🍠🥒diet with 2 meals per day works best for me. Unfortunately, I'm sitting in the office the whole day 💺

  6. I did three cycles of the Fasting Mimicking program and found that if I didn't ease back into feeding my blood pressure went through the roof. I already have an issue with blood pressure, so this may not be a common side effect of eating too quickly after an average fast, but if did freak me out. I was not expecting it and thought I might need to go to the emergency room. Lesson learned. Cheers!

  7. Really seems like IF and max 36 hour fasts are the way to go and that multivitamin supplementation should accompany both.

  8. Thanks for this Doc. There’s nothing magical about fasting, and if there’s dangers, people really should be informed. If benefits can be attained with safer means- why would you take the risk?

  9. Ooooh boy. Dr Greger's cohorts who promote fasting and make $$$$ are not going to like this one. LOL. I figured this didn't make sense and I was right. No need to fast on a WFPB diet . Stop destroying your body on non sustainable silly fads.

  10. Wow, speaking of bullshit to the nth degree. Everything done to the extreme will result in adverse effects even if you eat ONLY kale everyday for a year. So what is your point? Again your studies are mainly from the 60's. Not the best source of data considering the liturgy of science in the past 10 years . You do know we are in the 2000's right? You are still following that dogged tiring theme of skewing information to fit into a neat little box that only you confine yourself to. The point about scurvy in a few days and thiamine deficiency is not beyond the realm of possibility,so is getting hit by an asteroid. Looking at things in black or white is not science, its idiocracy. Any relation to Ancel Keys perhaps? You certainly seem to be going down the same rabbit hole he did.

  11. Did you find the worst cases for fasting? Fasting is very beneficial for the body. Jesus said when you fast not if you fast. Everyone should do it. Except pregnant or breastfeeding women.

  12. All of your examples were people who were too stupid to do an extended fasting properly, or were deathly ill to begin with.

    If you fast for extended periods and take electrolytes and supplement with vitamins you will be fine.

    Refer to the fasting fat man channel. He did a 150 fast with no problem this year. And is now about 30 days into another fast. No issue.

    Finally , using papers on starving have no relation to obese people fasting. Obese people do not starve when fasting. They have ample fuel storage to sustain them.

  13. This seems like some questionable science. I have done many water only 2 week fasts over the years. Most Americans are severely malnourished, so it makes sense that fasting would rapidly exacerbate that condition for such people. Also, the usual advice is to rest while fasting which is just bad advice. Lying around for extended periods of time will lead to muscle loss whether you are eating or not. Obviously, you should not engage in activities that result in sweating as the loss of electrolytes could certainly be problematic. I wouldn't advise fasting for more than 2 weeks at a time. There are too many horror stories about that to be worth the risk. For me the benefits have been the slight loss of 10-15 #'s of body fat and to easily reset my diet after the fast. During the course of the year, my habits get corrupted by those around me and I end up over eating and not being nearly active enough. Right now, I am doing less than 20 miles of running a week which is pretty sad.

  14. This is classic Dr Greger… Cherry pick a few studies that don't represent the majority of the small community of individuals who fast for health reasons. Using satire to passive-aggressively suggests that people who fast are going to die. Most people who attempt intermittent fasting are healthy individuals who are very health conscious and striving to restrict calories in a reasonable way for longevity. Caloric restriction and longevity are very closely correlated. Vegan or not.

  15. All types of fasting are unnecessary and idiotic. Both are starvation. It’s like you people are anorexic, thinking you are so fat so you may as well not eat to try and loose weight. Why not focus on healthy foods instead of perceived short cuts.

  16. Whenever someone in the keto+fasting community has heart issues they shrug it off and say “electrolytes!” As if all their issues will be solved by drinking salt water. The solution is don’t do keto or fasting.

  17. And now, WHAT ABOUT AUTOPHAGY, INTERMITTENT FASTING and Nobel Prize ??
    I eat OMA plant based food with ocasionaly very small quantity of fish in 4-5 hours window and have no problems.

  18. It is not advised by the experts in this field (Fuhrman, Godhaamer, Klaper, et al) to fast for weight loss. Water only fasting is done for health and healing. Please address those benefits about fasting (of which there are not many studies, but people have been doing it for a millennia). Thanks

  19. As medical supervision during WOF is a must, what testing should we make sure is performed? Is urine analysts enough? mAre blood tests necessary? How soon or often should testing be done? Comas are bad!!

    I know there’s is a center near Montréal (Val Santé) that supervises fasts but it isn’t clear what testing is performed.

  20. Another issue with fasting more than 12-24 hours as pointed out by Nathan Pritikin https://www.youtube.com/watch?v=BcHHDmuyPv4: when your glycogen stores start running low, the liver starts dumping a bunch of fat in the bloodstream. This results in a diabetic blood glucose spike upon reintroduction of carbs, the same response as those eating high fat keto diets.

  21. One meal a day is very sustainable. These 7 day starvation people think they've accomplished something but it's really short term. It's not a dick measuring contest.

  22. This is great! However, I would really love videos on intermittent fasting (16 – 20 hours a day) for weight loss/health/cells etc vs long term fasts for days. Pleaseeeeeeeeeeeeeeeeeeeeeeee

  23. The reasons why fasting longer than 24 hours, and particularly three or more days, should only be done under the supervision of a health professional and preferably in a live-in clinic.

  24. I don’t think you should conflate deaths from fasting in ghettos and wars and case studies of fasting ddeaths from decades ago before people understood electrolyte supplementation and modern day therapeutic fasting. More recent fasting studies have shown adverse events but rarely anything life threatening. I would like to see fasting compared with gastric bypass for obese patients- I think fasting is likely safer and more effective. Also- a low calorie diet is great but many people find eating very low calorie to make them much hungrier than fasting- the latter is more effective. But always I appreciate the balance of your videos. The first one was fairly positive.

  25. are these fasting series applicable to the trending Intermittent Fasting? If not, a series about IF would be pretty good.

  26. I watch, much appreciate and promote your vids, however, I have been looking for your research on intermittent fasting and seem to be finding only info on long term fasting. I think few people today are interested in straight, long term fasting.

  27. I have been a fan of Dr. Greger for years, but this is probably the worst video I have ever seen.
    Dr. Greger is trying to discredit fasting by confusing the subject with prolonged "starvation".
    Quoting decades old literature on "starvation" and then serving it as the side effects of fasting is absurd.
    Fasting is not starvation !!!
    Very disappointed !!!

  28. I heard that liver and kidney functions change during fasting. I wonder how this impacts multivitamin consumption during the process? Does the RDI change? Also, I’ve heard that ingesting sodium to taste is recommended in longer fasts, but what about potassium and magnesium?

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