FBS immediately after intermittent fasting

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FBS immediately after intermittent fasting

This topic contains 1 reply, has 2 voices, and was last updated by  Domen Leskovec 6 years, 6 months ago.

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  • First of all, I would like to thank Michael and Mimi for brining out this wonderful book.

    Myself and my wife began watching the fast diet documentary which was aired here in Australia in mid March 2013. Ever since, we have fallen in love with the 5:2 and we immediately began the diet. However, we couldn’t continue for more than a month due to several factors.

    Nevertheless, from past 3 weeks we both have been back on the diet, but with 6:1 in addition to skipping breakfast on weekends.

    Just to give a bit of background, my wife had gestational diabetics and she was on insulin injections from 26 weeks up until delivery (June 2011). During this period, she carefully monitored the blood sugar (BS) and was quite within the limit. Post delivery (several weeks) there was a glucose tolerance test done to make sure her BS was back to normal and indeed it was.

    In May 2013, our GP advised to get a fasting blood sugar (FBS) test along with other parameters to determine how the BS was and also to see if she was deficient with B12 and iron. Being vegetarian, she had a previous history of B12 and iron deficiency. Anyway the blood test was done and the FBS came as 5.9 mmol/L and the doctor said that she was in the “pre-diabetic” category and to check back in a few months. Apart from that she was deficient in B12 and iron and was given some supplements.

    From September my wife began cutting on rice and wheat based foods completely from her diet, just to shed some of her pregnancy weight and to have an overall healthy outlook. Being vegetarian, her diet since September has been rolled oats + milk for breakfast, various lentil + legumes + vegetables + eggs as salads for lunch and similar for dinner. Also, complementing with fruits most of the days. Adding to this, as previously mentioned she started back on 6:1 intermittent fasting since 3 weeks. She was curious to see how her FBG would be after the diet regime and with other vital parameters and decided to get the fasting blood test done. She finally got it tested last Wednesday (13th Nov) morning and the previous day (Tuesday) was her fasting day. Hence, she had not eaten anything for breakfast nor lunch and only had dinner at 7:30 on Tuesday. The next day at 9:00 was the blood taken for testing.

    We went to our GP yesterday and we were quite surprised to note the FBS had increased to 6.1 mmol/L and we dint have any explanation as to why an increased value despite on a good diet regime over the last 3 months. Or GP suggested to get the next test done after few days of fasting to see if that has any affect. Apart form that, she has lost 3 kgs, and her good cholesterol has increased, triglycerides has reduced within the safe limits. B12 and iron are fine now.

    So I am curious to see any possible explanation here in this forum about the increase in FBS immediately after the intermittent fasting and if some one has similar experience.

    Many Thanks.

    I believe this is a typical case of physiological insulin resistance.

    Please read this blog for an explanation. This guy explains physiological insulin resistance that happens when someone limits carbohydrates in his diet. I believe the same happens when fasting:


    I think that HbA1c – glycated hemoglobin would be more appropriate test for your wife. HbA1c provides an average of your blood sugar control over a 6 to 12 week period. If this is within normal range – 4 to 5.6%, I wouldn’t wory about slighltly elevated fasting blood sugar after a day of fasting.

    You can test her fasting blood sugar after a day of eating lots of carbs – oats, high sugar fruits. I expect it to be lower.

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