Longer fasts, ketoacidosis and weight regain

May 15 2016 by , medical content by in About membership, Dr. Jason Fung, Intermittent fasting, Q&A

There are tons of questions about intermittent fasting, like these

Should you expect to regain some of the weight lost after breaking a long fast?
Ketones tend to go up during longer fasts – is there a risk of ketoacidosis?

Dr. Jason Fung is one of the world’s leading experts on fasting for weight loss or diabetes reversal. Here are a his answers to those questions and more:

Fasting, ketoacidosis and weight regain

I’m not diabetic and I’m not on any medications. I’m now 5.5 days into my 7-day fast and I feel great! I’ve been monitoring my blood sugar and ketone levels every 12 hours. Over the 5.5 days my blood sugar average is 81 and my ketone average is 4.1. This morning my blood sugar was 66 and ketones 5.4. I don’t think I should be concerned about ketoacidosis but I can’t help it, as my ketones get progressively higher I can’t stop thinking about it. Please put my concerns to rest…

Is there any risk of my ketones going too high if I’m NOT a type 1 diabetic? I have been at a weight loss plateau for months even while eating strict LCHF and following a 16:8 eating plan. In the 5.5 days of fasting I’m down 7 lbs! In your weight loss management program, do you find clients are able to keep the weight off (after a long fast) when going back to an LCHF eating plan?
Thank you so much!!!!
Crystal

Crystal,

Ketoacidosis mostly happens in type 1. Ketones are supposed to go up during fasting – it’s called starvation ketosis.

There will usually be some weight regain after the fast, so be prepared. Generally, you can expect to lose 1/2 pound per day of fasting on average. For 7 days, that’s 3 1/2 pounds. Everything else could be water weight which will come back, and it would still be OK. It doesn’t mean the fast didn’t work.
Dr. Jason Fung

Very low blood sugar

Hello Dr. Fung,
I just started fasting after reading your blog post series. I’ve never tested blood glucose before and thought I’d try it with this fast and just bought a meter. I know you can’t give specific medical advice, but could you tell me from your experience with your patients…Do you feel a blood glucose reading of 39 on Day 3 of a fast falls within acceptable levels or do you feel that is too low? I have no symptoms and feel fine.

Airla

Airla,

If you are taking diabetes medications then yes, it is too low. If not, the main thing is to make sure you are feeling well.

Dr. Jason Fung

Higher blood glucose when fasting

Hi Dr. Fung,
I was diagnosed with type 2 a month ago. my fasting glucose was 386. I started fasting and LCHF and now a little less then a month later my average number is 115! My Dr. wanted to put me on medication and I said no I will try this ? So glad I found your Youtube video! I am wondering why sometimes when I fast for 34-48 hours my glucose is actually higher then on days I am eating?
Thanks!
Beth

Beth,

Dr. Jason Fung: This is similar to the Dawn Phenomenon, Read my post here – Dawn Phenomenon

Dr. Jason Fung

Intermittent Fasting for Beginners

Videos About Intermittent Fasting and Diabetes

How to Maximize Fat Burning – Dr. Jason Fung

How to Fast – The Different Options – Dr. Jason Fung

The 7 Benefits of Fasting – Dr. Jason Fung

The Top 5 Myths of Fasting – Dr. Jason Fung

Breakfast! Is It Really That Important? – Dr. Jason Fung

The Most Common Questions – Dr. Jason Fung

5 Tips to Make Fasting Easier – Dr. Jason Fung

How to Get Started with Fasting – Dr. Jason Fung

The Power of a 7-Day Fast – Dr. Jason Fung

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10 comments

1
Donna
May 18 2016
I have been on the LCHF plan for 14 days and have lost 9 lbs . Yesterday I began having lower back aching. By 24 hours later it is interfering with with sleep. Could this be a result of the diet?
2
Zepp
May 22 2016
Probably more about that you got stuck on watching more videos about LCHF!

Then rise up and take a long walk.
3
Em
June 2 2016
Hello LCHF and fasting experts,
I'm currently bedridden because of a broken bone.
I read that healing requires a lot of protein, so I'm eating well (while not hungry)
But today I read this article about broken bones and fasting (British Institute of osteopathy) and now I second guess my strategy.
So... Thoughts anyone? Te eat or not to eat, that is the question.....
Thank you for the input.
4
janet
June 22 2017
Hippocrates said if you eat when you are sick, you're feeding the illness. Let your body use your stored energy, fat to heal itself.
Fast on my friend !
5
Nate
June 22 2017
Good news: http://www.livinglifehealthyandfit.com/diet/ucla-medical-center-launc...
6
Bruce
July 13 2020
I am a type 2 diabetic. I stopped using insulin when I started keto style eating. If I go back my old ways in a few days I have high blood. however this year I do keto most of it. I normally am sitting around .2 ketones. Anyway, I wanted to try a long fast. I am now day 6 on my water fast and my blood sugars are 6.0(Australian measurement) I have a breath ketone meter and as of today, I reached the max 1.0 of the reader. I am afraid of ketoacidosis, I was told it happens when the ketones are over 1.0 and since I am there now is this dangerous for me? I don't feel weak or hungry and besides missing my hobby of eating everything is fine, I had a headache from 24 hours to about 40 hours of the fast I assumed it was detox. I took some paracetamol around 40 hours the headache went and since no issues. I have been taking a teaspoon of salt every second day.

As I said I don't feel unwell and can easily keep going, but the high ketone today has scared me. Please advise also I can't go to doctors because I am out of my country caught in the coronavirus lockdowns.

Reply: #7
7
Reply to comment #6 by Bruce
Crystal Pullen Team Diet Doctor
July 13 2020

I am a type 2 diabetic. I stopped using insulin when I started keto style eating. If I go back my old ways in a few days I have high blood. however this year I do keto most of it. I normally am sitting around .2 ketones. Anyway, I wanted to try a long fast. I am now day 6 on my water fast and my blood sugars are 6.0(Australian measurement) I have a breath ketone meter and as of today, I reached the max 1.0 of the reader. I am afraid of ketoacidosis, I was told it happens when the ketones are over 1.0 and since I am there now is this dangerous for me? I don't feel weak or hungry and besides missing my hobby of eating everything is fine, I had a headache from 24 hours to about 40 hours of the fast I assumed it was detox. I took some paracetamol around 40 hours the headache went and since no issues. I have been taking a teaspoon of salt every second day.
As I said I don't feel unwell and can easily keep going, but the high ketone today has scared me. Please advise also I can't go to doctors because I am out of my country caught in the coronavirus lockdowns.

Diet Doctor is not able to provide medical advice. You can see in a similar question above from "Crystal" that Dr. Fung states, "Ketoacidosis mostly happens in type 1. Ketones are supposed to go up during fasting – it’s called starvation ketosis."
8
Matt
January 18
Bruce! Do not take paracetamol while fasting any longer than a day. Healthy people on a two day water fast have presented with liver failure after taking the recommended dose of paracetamol. Fasting drastically lowers the amino acid (NAC) required for the liver to process paracetamol so that normal dosages can destroy an otherwise healthy liver. See this article: https://pubmed.ncbi.nlm.nih.gov/19391450/
9
Bobby
March 9
Dr. Fung, I did a 50 day fast 2 years ago after reading bits and pieces of your writings because I could get a hold of your book. I figured Christ did it for 30 days so with His help I could do it and did so and lost 40 kilograms of weight of which I regained 15 kg. in the past 2 years. 2 months ago, I got a bacteria infection and my blood sugar spiked to 485 so the doctor checked me into the hospital where I spent 10 days getting 5 antibiotic shots per day. I finally returned home and started a low carb meal plan. 5 days ago, I decided to do another water fast because I still have lots of kg. to loose. In the past 5 days, I've lost 8.8 kg. of weight. I know most of it is water. My blood sugar today was between 116-141 mg/dl. I've stopped taking all Metformin and Miniadab as of 2 days ago. My family is worried that I could develop kitoacidosis and want me to stop the water fast. From your book, "The Complete Guide to Fasting" which I finally was able to get, on page 121 you state, "If you don't have type 1 diabetes, don't worry: you won't develop ketoacidosis!" So, my question to you is this. Should I worry about developing ketoacidosis? I'm a missionary and live in Thailand and most doctors here are terrified of the Water Fast. The last time I did the fast, my doctor was worried stiff about the high levels of my ketones. Should I be worried. You mention that is to be expected in a water fast and say don't worry. I can't afford to join your group but want to buy the Obesidy code to further educate myself. Please answer my email. Thank you so much.

Reply: #10
10
Reply to comment #9 by Bobby
Kristin Parker Team Diet Doctor
March 9

Dr. Fung, I did a 50 day fast 2 years ago after reading bits and pieces of your writings because I could get a hold of your book. I figured Christ did it for 30 days so with His help I could do it and did so and lost 40 kilograms of weight of which I regained 15 kg. in the past 2 years. 2 months ago, I got a bacteria infection and my blood sugar spiked to 485 so the doctor checked me into the hospital where I spent 10 days getting 5 antibiotic shots per day. I finally returned home and started a low carb meal plan. 5 days ago, I decided to do another water fast because I still have lots of kg. to loose. In the past 5 days, I've lost 8.8 kg. of weight. I know most of it is water. My blood sugar today was between 116-141 mg/dl. I've stopped taking all Metformin and Miniadab as of 2 days ago. My family is worried that I could develop kitoacidosis and want me to stop the water fast. From your book, "The Complete Guide to Fasting" which I finally was able to get, on page 121 you state, "If you don't have type 1 diabetes, don't worry: you won't develop ketoacidosis!" So, my question to you is this. Should I worry about developing ketoacidosis? I'm a missionary and live in Thailand and most doctors here are terrified of the Water Fast. The last time I did the fast, my doctor was worried stiff about the high levels of my ketones. Should I be worried. You mention that is to be expected in a water fast and say don't worry. I can't afford to join your group but want to buy the Obesidy code to further educate myself. Please answer my email. Thank you so much.

Dr Fung recommends medical supervision for longer fasts specifically to monitor blood sugar, blood pressure, medications and more.