Fatigue day after fasting

This topic contains 13 replies, has 10 voices, and was last updated by  parrotmom 8 years, 8 months ago.

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  • Hello, I first read about IF in the NY Times article about 2-3 weeks ago, immediately watched the BBC documentary and devoured the book in record time. I began 5:2 about 10 days ago and my fast days are Monday and Thursday. On fast days, I eat all 500 calories in a single meal (heavy in protein & veg) around 7pm. My goals are to lose weight and improve my cholesterol and triglyceride levels. I am 46 yo, overweight and need to lose about 40 pounds. I exercise 6 days/week with a routine that alternates cardio, weights and yoga (exercise compliance has never been my problem). On non-fasting days, I eat within my TDEE and generally have a healthy diet low in processed foods; I have a glass of wine once or twice a week with dinner.

    I just completed my third fast day. The only side effect that bothers me is a marked increase in fatigue and very low energy the day immediately following a fast. I cannot concentrate well and feel distracted. On fasting days, I do not have any energy problems and have no trouble with mental focus. No history of low iron or thyroid here. I have even toyed with the idea of moving to a 4:3 regime to avoid the fatigue, but I want this to be a permanent lifestyle change, so I want to take things slowly and do what feels manageable.

    Has anyone experienced these dips in energy on days immediately following a fast? I hope this is just my body adjusting to the fasting and will disappear soon. It’s discouraging to feel so tired. The fatigue is usually not a problem on the second day after a fast.
    Thanks in advance for your feedback!

    Broomhilda

    Hi Broomhilda (I really like your name) 🙂
    When I first started fasting I experienced the same thing and couldn’t fall asleep due to being waaay too wired – now it’s become the opposite for me: I get kind of tired on fast days, but feel really energised the day after, and wake up much earlier than I ever would before – but even the fast day tiredness is dissipating for me. So I definitely think your body is just trying to find out what’s going on. Perhaps you could do some exercise on your non-fast days to combat the fatigue? That worked for me at least…

    I hope you’ll find out what works for you! Just be patient 🙂
    Alexa x

    I find that I’m just waking up every two hours to run to the bathroom on FDs…all that water/tea/miso, etc. So I wake up from a FD very tired.

    Alexa – thanks for the encouragement. I hope I can get to the point where I am not feeling draggy after the fast day.

    K-Lo – I hear you on the nighttime waking. I have the smallest bladder in the world, it seems!

    Thanks for the feedback!

    Broomhilda

    Hi Broomhilda,

    I can’t help with the fatigue, but just want to say you’ve got a great name! 🙂

    Cheers and good luck,
    Austrian

    Hi Broomhilda(I love your user name too!)
    I haven’t had that fatigue you describe, I do hope you can figure it out.

    Could it be dehydration? Many people experience this when they begin 5:2, mostly with headaches or dizziness on fast days, but it is possible it catches up with you the day after. You need to drink heaps of water on your fast day, and have salty things too (osmosis!).
    If you are going to bed a bit dehydrated, you will wake up, 7 or so hours later, much more dehydrated. Hence foggy and tired.
    If this might be the case, have lots of water through your fast day (several litres!), with salty things (thin soups are great). And to avoid being up to the loo all night, slow them down over the last few hours before bed. This might be worth a try.

    Good luck to you!

    PS K-Lo, I find that if I don’t have cups of tea after about 4pm, I don’t have to get up through the night. I think it is the tannins that irritate the bladder.

    Thanks for the feedback everyone. I have an update of sorts. I had my annual physical last week and three days ago, I received my blood test results which show that I have an overactive thyroid. So I am hyperthyroid right now. My last fast day (immediately following Easter Sunday) was the easiest so far and I did not experience the post-fast fatigue, so perhaps it was an adjustment issue or it’s connected to being hyperthyroid.

    Broomhilda

    I find that I have a definite lack of energy the day after I fast, but by the afternoon I normally feel fine again. I also have trouble sleeping after fasting and toss and turn for an hour at least after I go to bed.

    I am at the end of my first week on the diet,so have completed just 2 fast days (Mon & Thu). I also felt VERY tired the day after fasting. I felt I could not concentrate very well. I worked 3 early shifts in a row and by the end of Wednesday I was relieved I had 2 days off to recover, but of course Thursday was another fasting day. I tried to keep drinking water, but when you are out on patch it’s not so easy to find toilets you want to use. I do hope things improve as my body gets used to it. Me and the diet will fall out, if I can’t work safely.

    Veggie Digger,

    You’ve just done 2 days (one week). Give it 4 to 6 weeks. Your body is most likely just relying on glucose to function. The other energy source is fats converted to ketones and that system hasn’t probably needed to work for many years if you are overweight. Its a bit like saying, Ive jogged 1 mile the last two days, I think Im ready to do the NY marathon now. Unrealistic. Give your body a chance to start making ketones as your energy source. At the moment your body would rather run down your glucose levels rather than flip to fat (ketones). Give it 6 weeks.

    Hi Bigbooty

    Yeah, you’re right. I was just feeling low. Just completed my second week on the diet now. It will be interesting to see how I feel next Wed, when I will have completed the next run of 3 early shifts in my 2-weekly shift pattern. On the bright side, I just moved my mum into her new flat and yesterday was an emptying boxes and sorting stuff out day as well as a fast day. I’m going back to finish off today – but this time with food in my belly. Feeling OK. Thanks for your support.

    I agree with BigBooty. I started with a week of low carb before I began 5:2 and had very similar symptoms to those being described, wired overnight, lots of loo visits in the night etc but they settled within the week. Then I started 5:2 and had some tiredness the following day. I split my 500 cals into three at that time, which seemed to help, though now I eat brunch at about 12 and supper at about 8 pm only. Sometimes I’m still a bit fatigued in the morning but I’ve been upping my exercise too so that may be the cause. Seems to have settled generally, though I find if I’ve had carby food like bread or cake on the day before the fast I feel more cravings, so keeping off starches does help.
    I’ve lost 12lbs in 10 weeks, which is great. My goal is 28 lbs, after which I’ll consider another goal. I’ve lost 5 ins off my waist, so pleased about that as that means visceral fat is going. So hang in there you guys! It works!

    I am new to 5:2 i just did my first fast and weighed myself the following morning. i lost and waited 2 days and i am doing my second fast so i weight myself this moring, what i lost all came back..is that normal it hasn’t been a week yet. i have been seeing a nutritionist for some time and have been at a plateau for 3 month and she suggested that i try this..any suggestions would be greatly appreciated

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