The Dark Side of Fasting (and Intermittent Fasting): Dr. Berg Explains

Is fasting dangerous? It can be. Check out the dangers of fasting and how to avoid them.


Baby Food Alternatives:

How to Break Your Fast:

Refeeding Syndrome:

0:00 Introduction: Is fasting dangerous?
0:10 Benefits of fasting
0:16 Fasting explained
1:15 Dangers of prolonged fasting
13:58 Learn more about how to do intermittent fasting!

Today, let’s talk about the benefits and dangers of fasting.

Some of the top benefits of fasting include weight loss, cognitive improvements, and enhanced heart function.

Most of the dangers of fasting I’m going to cover aren’t related to a 16 to 18-hour fast. This applies more to prolonged fasting, which is when a person fasts for 48 to 72 hours—or even longer.

The purpose of eating is not just to get fuel. It’s also to get nutrients. When you’re fasting, you’re restricting nutrients. If your diet isn’t providing you with the nutrients you need when you do eat, you could end up with deficiencies that lead to certain issues.

It’s crucial to do a prolonged fast correctly and avoid common mistakes related to the dark side of fasting.

The dark side of prolonged fasting:
1. Refeeding syndrome
When you come off of a fast, have a small amount of food, wait a couple of hours, and have a little bit more. Avoid overeating or eating carbs.

2. Dirty keto
Make sure you consume nutrient-dense, high-quality foods on the keto diet.

3. Not taking nutrients while fasting
At the bare minimum, you need to take electrolytes, sea salt, trace minerals, and B vitamins while fasting.

4. Kidney stones
Avoid high-oxalate foods if you’re prone to kidney stones. Also, consume at least two and a half liters of fluid a day, and add lemon juice to your water. When you’re back to having meals, consume large salads.

5. Anorexia
Anorexia will cause nutritional deficiencies. Instead of fasting, get on the keto diet.

6. Athletes that have not adapted to fat yet
Give your body enough time to become fully fat-adapted before attempting prolonged fasting.

7. Fasting for children
Fasting isn’t a good idea for children. Eating three meals a day and cutting out snacking may be beneficial for children. Teenagers who are overweight may consider two meals a day without snacking.

8. Not getting enough nutrition while pregnant or lactating
Not getting enough nutrients while pregnant or lactating can lead to issues for the mother and child. Choosing a whole-food, natural prenatal vitamin over a synthetic prenatal vitamin is also important.

9. Muscle loss
If you’re older and noticing muscle loss, try adding a blend of amino acids to your diet.

10. Ketoacidosis
This rare condition occurs in people under very specific circumstances and isn't something most people should be concerned about.

Dr. Eric Berg DC Bio:
Dr. Berg, age 58, is a chiropractor who specializes in Healthy Ketosis and intermittent fasting. He is the author of the best-selling book The Healthy Keto Plan, and is the Director of Dr. Berg Nutritionals®. He no longer practices, but focuses on health education through social media.

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Dr. Eric Berg received his Doctor of Chiropractic degree from Palmer College of Chiropractic in 1988. His use of “doctor” or “Dr.” in relation to himself solely refers to that degree. Dr. Berg is a licensed chiropractor in Virginia, California, and Louisiana, but he no longer practices chiropractic in any state and does not see patients so he can focus on educating people as a full-time activity, yet he maintains an active license. This video is for general informational purposes only. It should not be used to self-diagnose and it is not a substitute for a medical exam, cure, treatment, diagnosis, prescription, or recommendation. It does not create a doctor-patient relationship between Dr. Berg and you. You should not make any change in your health regimen or diet before first consulting a physician and obtaining a medical exam, diagnosis, and recommendation. Always seek the advice of a physician or other qualified health provider with any questions you may have regarding a medical condition.

#keto #ketodiet #weightloss #ketolifestyle

Thanks for watching! Avoid the dangers of fasting by following these tips. I’ll see you in the next video.


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  1. @RobCLynch on October 19, 2023 at 10:16 am

    Intermittent fasting was the best thing I ever discovered…on this channel. Thanks Doctor Berg.

    • @mattmcarthur8054 on October 19, 2023 at 10:39 am

      Agreed, changed my life n will never go back.

    • @Avengedsevenfoldrocks on October 19, 2023 at 10:43 am

      Are you in Florida?

    • @RobCLynch on October 19, 2023 at 10:56 am

      @@claytonallisonallison8758 I’m not in Florida, I’m in the UK…if you’re referring to me lol.

    • @stevensilver6298 on October 19, 2023 at 11:04 am

      Changed my life for the better.

    • @Sum1snrg on October 19, 2023 at 12:08 pm

      I second that comment!

  2. @christinavanmeter5034 on October 19, 2023 at 10:17 am

    I love your videos! You are truly helping people. The content on your channel is giving people the information they need to take back control of their health. Thank you for using your knowledge for the good of others. God bless you!

    • @Drberg on October 19, 2023 at 5:57 pm

      Glad to help you all. Stay safe and healthy!

  3. @sexenbayeva96 on October 19, 2023 at 11:26 am

    After I watched your videos and started healthy Keto + IF I lost more than 60 lbs this year! Around 10 lbs a month! Thank you ❤

    • @Drberg on October 19, 2023 at 2:58 pm

      Good job. Keep up the good work. Would you like to share your Keto/ IF success story on my website? I’d be happy to see your story there. Feel free to upload your story here:

    • @julie9155 on October 22, 2023 at 5:18 pm

      ​@DrEricBergDC out of the following supplements which are proven to work best together or separate with least side effects: Berberine, Betaine HCI, Magnesium. Choline Inositol and Alfalfa. For energy, weight loss, digestion and least damaging to our organs?

  4. @mekman4 on October 19, 2023 at 11:40 am

    This is incredibly informative. And now that the genie is out of the bottle, tell me about the pancreas and how we destroyed that with our previous high carb diet and how to fix it!

    Thank you! Always!

  5. @reneewhittinghill3440 on October 19, 2023 at 12:35 pm

    I just tried cutting carbs to less than 50g per day. I couldn’t sleep at all by the 3rd night. I used to have no problem fasting when younger. Dr Mindy Pelz talks about only fasting during high estrogen at the beginning of your monthly cycle but not after ovulation during high progesterone at the end. So many health suggestions seemed to get reversed after a couple of years for women. Turns out we are not men and often need to do the opposite. I was at my healthiest when doing a diet called Creating Wellness by Patrick Gentempo DC. It had 3 meals and 2 snacks and counted portions of protein, carbs, and fat. I think we just have to admit that we are all different and you have to do what works for you. I’m glad you are sharing more on genetic testing! I think that will help explain why certain things work better.

    • @McCafferyProdz on October 19, 2023 at 1:08 pm

      I just turned 50 and had tried intermittent fasting for months and couldn’t lose weight. Frustrated, I went to a nutritionist and she said IF doesn’t work for alot of people, especially middle age and older women.

    • @TheAMW on October 19, 2023 at 2:53 pm

      I like her and follow her also but I have fasted for 7, 14 and 30 days and the position of my cycle never is a factor. I say do what works for u.

    • @jackiedelvalle on October 19, 2023 at 7:30 pm

      ​@@McCafferyProdz I’m mid 50s and have been doing it for over a year. It’s worked amazingly, when huge exercise and tonnes of carbs (mainly fruit, following govt guidance) didn’t budge a pound and left me painful and swollen. It has honestly been miraculous for me. I feel mid 30s.

    • @gingercameronfordcrouch7057 on October 19, 2023 at 9:49 pm

      @@TheAMW I’m on day 5/6 plan on at least 28 have you gone any longer than 30. Have heard of others doing much longer and did well. Ghandi and others!

    • @drseanpatrick696 on October 20, 2023 at 2:03 am

      Women need to stop modeling their health after men. You need more sleep than a man. Your hormonal cycle is roughly 28 days compared to the 24hr cycle of a man. You don’t tolerate fasting as well as a man. You aren’t as stress resilient compared to a man.
      Women are not small men.

  6. @TheSilentListeners on October 19, 2023 at 1:26 pm

    Simple daily 16 to 18 hours fasting even does the wonder. I have been on 18 hours fasting for one and half years and these are my results:
    1. fat loss 126kg to 72kg
    2. high testosterone level from 239 to 598
    3. All clothes are loose and i have to give to obese people 😀
    4. waist 52 inches to 32 inches
    5. energy levels are always up
    6. Appreciation from people and high motivation level.
    who cares for 4 6 days fasting when you are getting all health benefits from 16 or 18 hours.

    • @TheAMW on October 19, 2023 at 2:55 pm

      Bc after u have been doing that for a while the body gets adapted and u move to 48-72 hours or more to get benefits

    • @COMPUTER.SCIENCE. on October 19, 2023 at 4:33 pm

      Do you notice any difference between 16hr and 18hr fasting?

    • @sacq13 on October 19, 2023 at 5:15 pm

      Been on keto and IT since 2021, I only do 16- 18 hrs .. and I just recently started OMAD once a week..

      My sleep was affected badly, but I take magnesium at bedtime & almond milk and honey to counter insomnia

    • @robertavanselow9172 on October 19, 2023 at 7:02 pm

      My body just naturally went into 16-18 hours of intermittent fasting. Been doing it for years.

    • @franbatista9062 on October 19, 2023 at 10:36 pm

      The higher testosterone is also a consequence your weight loss and reduction estrogen levels that exist when having high body fat percentage. All in all, congrats! With exercise it’s even better

  7. @LAWMethod on October 19, 2023 at 1:37 pm

    I’ve been fasting for ~5 years out of the last 7 years, been known to get pretty extreme with it, but I noticed it’s a fine line you have to walk between fasting and an eating disorder

    • @susanchun2573 on October 26, 2023 at 5:46 am


  8. @Bubbaluv8 on October 19, 2023 at 2:18 pm

    Thank you Dr. Berg for rounding out my fasting intel, the goods and the bads 👌

  9. @patriciau6277 on October 19, 2023 at 2:29 pm

    17 to 24 hour fast is very easy never had any problems. I’m just getting into fasting longer. What I have noticed so far is if I’m not starting out with a keto lifestyle longer fasting has problems. I love fasting. After day two is when I feel the benefits and it’s easier to go longer each time. I stopped eating ALL sugars and glucose products back in January. The difference is great. I don’t miss them. I cheated a few times and felt sick afterwards. I don’t enjoy those products anymore.

    • @latentsea on October 20, 2023 at 4:35 am

      Sugar is like a drug . So much better being free of it.

  10. @NoseyFloridaGirl on October 19, 2023 at 3:56 pm

    I fast every day but only between 13-15 hours. I’ve never felt better . I don’t do prolonged fasting. Thx Dr Berg 😊

    • @Worldpeace353 on October 19, 2023 at 6:20 pm

      Me too It works well

    • @annettefowler4704 on October 21, 2023 at 6:33 am

      Me to. I,feel comfortable .

    • @annettestephens5337 on October 21, 2023 at 7:20 am

      2 meals a day, resting my guts for about 16 hours and eating low carb whole foods is how I will eat til the end

    • @mrmaxaxl on October 24, 2023 at 5:23 pm

      Me too! 3 hours between every meal 😃

    • @rollianders5550 on October 25, 2023 at 9:33 am

      Start eating lunch betwern 12:00-14:00, take a nap, and have tea time/ dinner between 16:00-19:00.

      Reduced carbs, add. protein from eggs, curd, legumes, meat, nuts (walnuts) mainly. Bread I make myself with added Proteine.

      Lost 25++ kg. 15 kg in 8 month, ½ year pause, 10++ kg in 6 month.

      5 times a week indoor rowing and 2-3 spinning.

  11. @jeremyowen5636 on October 19, 2023 at 4:01 pm

    Love everything you do Dr Berg! Keep it up please.

    • @Drberg on October 19, 2023 at 7:35 pm

      Thanks for your comment!

  12. @Perri_Redder on October 19, 2023 at 4:46 pm

    I’ve found that long term intermittent fasting has led to a very significant decrease in overall appetite. I recently found that I easily skip meals and I am not bothered by hunger to a greater degree. This means I now have to be quite mindful that I DO make sure I am getting the nutrients I need. Being diligent and mindful is the best tool in my case, and likely many others.

    • @lovetobe6118 on October 25, 2023 at 1:50 am

      I agree. My meals are also high calorie with most calories being healthy fats. My body needs healthy fat to function.

  13. @bloodybonescomic on October 19, 2023 at 5:42 pm

    I fast 24 hours once a week. Every two weeks I do a 48 -72 hour fast. Depends on how I feel. To break a long fast I usually grill a trout and eat some cooked dark greens seasoned with sea salt and butter.
    Now, I do take electrolyte suppliments during fasting. If I don’t I can get rapid pulses at night, some sciatic nerve pain in my left foot and a big loss of motivation.
    Once everthing is tuned the rewards are stellar. I am 65.

  14. @BabyGirl-yc2he on October 19, 2023 at 6:24 pm

    Intermittent fasting has really helped me loose weight that did not want to shift for 10 years. To think i am seeing weight loss in my 40s is bittersweet❤

    • @Drberg on October 19, 2023 at 7:42 pm


  15. @johnniejumper9810 on October 19, 2023 at 7:47 pm

    I love your videos. Great information brother. I actually started doing the keto after watching your videos. It’s a fantastic way to get into much better health. I have moved on to an all beef diet. It’s a simpler diet for sure but I feel great and I been doing it for 6 months now. I did do the healthy keto for several months first and intermittent fasting too. I still only have one meal a day. With a couple chocolate squares for dessert. It took me several months to adapt and I require a lot of sea salt. The sea salt can sometimes feel like a huge energy boost. 🎉❤😊

  16. @k8lynmae on October 19, 2023 at 10:45 pm

    My cousin here in australia had the worst and rarest breast cancer. She was in hospital and the person forgot to remove the previous patients Nil By Mouth card above the bed. No doctor or nurse questioned it. My cousin went a whole week without meals thinking her doctors had ordered it. My cousin finally asked a friend to ask why she is not allowed to eat. She did survive the breast cancer and is still in remission. I believe that long fast did her good. She would have had water and possibly some Drips

    • @corneliadennis2892 on October 20, 2023 at 5:42 am

      That is a freaky story. It’s like the universe was really looking after her!

    • @SpamMouse on October 20, 2023 at 10:34 am

      Wow. Glad she is progressing.

    • @spursdynasty7378 on October 21, 2023 at 4:47 am

      Great to hear ! Hope she gets better soon.

    • @bettyboop3206 on October 29, 2023 at 11:45 pm

      If someone ever diagnosed me with cancer, the first thing I would do would be to fast for 2-3 weeks. Then maintain ketosis. Lack of sugar starves cancer.

  17. @christopherbobin4268 on October 20, 2023 at 10:41 am

    The biggest problem I encountered when I started IF and keto was not taking electrolytes during exercise (I fast into my workout). It can cause some serious arrhythimia and it’s downright scary to experience. Now I take electrolytes and amino acids during my workout, as suggested by the good doctor here.

    • @chillgamer3164 on January 5, 2024 at 7:33 am

      hi, what exactly did you take while fasting?

  18. @bettyswallocks6411 on October 24, 2023 at 10:32 pm

    I’ve been doing 5/2 for a few years. It has highlighted a couple of deficiencies that I had not realised were there, now rectified. 67-yo, otherwise eating a varied mostly vegetarian (fish a couple of times per month + fish oil daily). I exercise regularly and sleep very well.

  19. @JanRossi on October 25, 2023 at 1:16 pm

    My body has lots stored away. I don’t do any 3 day fasts – that’s crazy to me. 18 – 22 hour fasts is all I do and I get very good results. People who are obsessive tend to go way longer and do end up hurting their system – my friends like this stopped those prolonged fasts. Really listen to your body everyone!

  20. @laurathurlow3634 on October 26, 2023 at 7:56 pm

    Hey Dr. Berg, I’m so grateful for your wisdom, guidance, and experience. How would I navigate this ‘incarnation experience thing’ without you?? I only do 20/4 max, I used to have hypoglycaemic seizures and I’m still too traumatized to fast for a whole day. You’re awesome, Dr. B, keep on rocking it!

    • @Blessednesting on November 8, 2023 at 5:28 am

      Drink bone broth if you want to do a 24 hour or fast from 5pm to 5pm next day, that way you’re still eating daily.

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