Do you recommend going in and out of ketosis?

Ask Dr. Jason Fung

What do I need to know about exercising while doing extended fasting? How much salt should I add to water when I’m fasting? And do you recommend going in and out of ketosis?

It’s time for this week’s Q&A about intermittent fasting and low carb with Dr. Jason Fung:

Exercising while fasting

Is there anything I should bear in mind regarding extended fasting and endurance training? I’m looking at starting some extended fasts of around 36 hours, but I will also be exercising quite heavily as I’m training for a marathon. Any advice would be really appreciated.

Chris

There is a period of adaptation, about 2-3 weeks to get your body used to exercising while fasted.

Dr. Jason Fung

Water fasts and staying hydrated

Hi Dr Fung,

Do you have a recipe for how much salt to add per one liter of water, for a person to drink while on a water fast to maintain hydration and electrolytes? Every person drinks a different amount of water each day so the question is if a person only drank this salted water and no other liquids.

Thanks,
Rachel

There is no single right answer. Some people don’t use salt at all. Others get dizzy if they do not take supplemental salt. The kidneys have an extraordinary ability to retain salt in the the event of sodium depletion. For shorter fasts (24-36 hours), it is likely not necessary to supplement.

Dr. Jason Fung

Going in and out of ketosis regularly?

Is it necessary or recommended that you switch out and into ketosis again on a regular basis? Online I read that some experts advise that, in order to maintain insulin sensitivity. For women I even read about a high-carb “week” during the menstrual cycle, altered with a ketogenic diet in the other 3 weeks. Or 5 days keto, 1 day fast and 1 day feast, with higher carbs.

I watched many videos on the dietdoctor website now (love it!) But have not come across any such advise yet.

Mirjam

I think it is beneficial to switch things up every few weeks, too, although most evidence is anecdotal. There is one small study MATADOR, that suggests this is true. In this study, alternating periods of calorie restriction with normal diets seemed to be better than continuous dieting. The same probably holds true for ketosis.

Dr. Jason Fung

 

 

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26 Comments

Top Comments

  1. Allen
    Thanks for the advice Jan, but trust me when I say that a lot of people on here had done what you said and got NOWHERE.

    And ketogenic dieting is NOT a fad. Low-fat diet is a fad, vegetarian diet is a fad, eating 11 servings of grains and massive amounts of sugar and treating a calorie like any other calorie is a fad. They have all failed.

    Some of us, myself included have lost lots of fat and been healthier than we have been in years. Personally i dropped 80 pounds, I am off all my HBP meds and my T2D is gone.

    So please, spare the advice that everyone that suffers from obesity has heard a million times before. It’s amazingly disrespectful to think that they haven’t tried that old saw before.

    Read more →
  2. Ed Wilcox
    .."the same 'probably' holds true for Ketosis?" What kind of professional medical advice is that? I suggest you do your research before providing an answer, or don't provide an answer.
    Replies: #7, #23
    Read more →

All Comments

  1. Ed Wilcox
    .."the same 'probably' holds true for Ketosis?" What kind of professional medical advice is that? I suggest you do your research before providing an answer, or don't provide an answer.
    Replies: #7, #23
  2. Lance Brown
    "I think it is beneficial to switch things up every few weeks, too, although most evidence is anecdotal. "

    Valter Longo's research is not anecdotal.

    Define beneficial...

  3. Deborah Kendryna Johnson
    I am a Keto person I it helped me get off a platue change my metabolism. I have now kept off for over a year and I do switch up I believe in listening to my body. I am very grateful for Keto and I switch to Paleo and very occasionally I have my indulge days. Grateful for Keto and Paleo I am healthier than ever before.
  4. Jan
    My gosh people... Just eat a well balanced diet and never get full... forget all the fads!!!
    Replies: #8, #26
  5. Cam
    You should never ever exercise during a fast besides something light. I'm not sure if this is an actual licensed medical practitioner or not. But intense exervise during a fast is extremely dangerous.
  6. Allen
    Thanks for the advice Jan, but trust me when I say that a lot of people on here had done what you said and got NOWHERE.

    And ketogenic dieting is NOT a fad. Low-fat diet is a fad, vegetarian diet is a fad, eating 11 servings of grains and massive amounts of sugar and treating a calorie like any other calorie is a fad. They have all failed.

    Some of us, myself included have lost lots of fat and been healthier than we have been in years. Personally i dropped 80 pounds, I am off all my HBP meds and my T2D is gone.

    So please, spare the advice that everyone that suffers from obesity has heard a million times before. It’s amazingly disrespectful to think that they haven’t tried that old saw before.

  7. Ethan Asamoah
    He clearly said before answering most of the evidence is ancedotal with exception of 1 small study he pointed to
  8. Jason
    Lol you don't know about keto if you think it's a fad. So why are you here troll? No other diet saves children from epilepsy, kills senescent cells, reverses diabetes etc. You dumb people are so prevalent. No wonder we got Trump.
  9. Laura
    Lmaooooo Jason facts!!
  10. Deb
    I want so bad to fast but my adrenal fatigue kicks my butt bad if I even put off breakfast s few hours ?
  11. Justin Lurker
    Jan, I've also heard an apple a day keeps the doctor away. Word.
  12. sara
    I lost 30 pounds on a KETOGENIC diet. I feel and look better now than I did 15 years ago.
  13. Anna
    I’m trying keto for a month but heart burn is really killing me. Taking PPI now and didn’t ever take it before but still now have horrible heart burn around the clock. How to stop it?
    Replies: #22, #25
  14. Patricia
    Anna, apple cider vinegar after each meal will get rid of heartburn. You can mix 1 tablespoon with two parts water if you can't take it straight up. I would quit all acid reducers before starting the cider vinegar though. Hope that helps.
    Reply: #24
  15. Escapology
    The moment when you realize that reading the comments answers more questions than the actual Q&As...
  16. Naomi
    For those who thinks Keto is a fad, maybe you have not tried it at all, I have tried so many fad diets and they all fail as they are not sustainable, keto is sustainable . I have lost 56 lbs and I am no on my normal weight of 113 lbs at 5'2". Thank you to all the doctors and experts behind dietdoctor. More power to you all
  17. Oscar Chalupsky
    I do normal training in the fasted state. I train about 2-4 hours a day. I have done many 24 and 48 hour fasts and 2 x 4 day fast. Will try do a 7 day fast next.
  18. Marilyn
    I had open heart double bypass would i prevail on a ketogentic diet??
  19. Rick
    Jason... I have a great respect for many of your postings, and I have a specific distaste for trolls, but I am disappointed with your reference to Trump. I don't see the connection with keto. Unfortunately, you got sucked in and the troll won. For what it's worth, my wife is a functional medicine physician, and I have recently been forwarding some of your postings to her. They are very informative. I have personally benefited from keto. Also, I think Trump was a far far better choice than the alternative, despite his flaws, and I don't consider myself "dumb".
    Rick
  20. Wade
    Completly useless Q&A that was Dr.s really know nothing about keto diets. I’ve lost 60lbs and never felt better in my life on keto in 1 year. My Dr had to ask me all about it. Anyone saying it’s a fad is completly false it’s a lifestyle for me and many other people. I will never go back to how I use to eat. However I would like to try one week of eating healthy carbs every few months. Wondering if anyone else tried this?
  21. David
    For myself Keto-OS has help me loose 18 lbs as of about two months. My appetite has changed, gotten to where I can say no to sugars and fats on my meals. I use Keto-OS every day and work out 2 to 3 times a week. My question is do I have to stop taking Keto-OS every now and then for it to be more effective? And how long are this breaks for ?
  22. Belle
    read "great taste no pain" diet info.. then apply info to keto.. it will stop.. really!!! once you understand the info its a whole new life
  23. Me
    Ummm ... it's NOT professional medical advice because they can't give professional medical advise over the internet. Chill pills are what you need.

    .."the same 'probably' holds true for Ketosis?" What kind of professional medical advice is that? I suggest you do your research before providing an answer, or don't provide an answer.

  24. steve bromley
    patricia -

    try miso. it works for me...

    light miso, dark miso, dissolved in hot water...

    it has not interfered with any aspect of fasting (now late in my third week) or my keto diet...

    good luck!

  25. Carolyn
    Hi Anna, I had to stop all things coconut, it gave me terrible heartburn! Sad because I love the taste. Also ACV should help sort it or even some lemon juice in a glass of water.
  26. Filipe Jorge
    Hi Jan, doing what you sad create in one year a Fat leaver disease, eating every two your is not a god advise, in this moment I'm doing Keto a IF for the last 7 months and I revert the leaver problem, I lost 9kg, 10% of visceral fat, and my analyses are amazing, so I recommend before talking or writing anything about Keto and IF read first, Google, is the best place to search.

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