Intermittent fasting and a no-sugar diet for Long COVID symptoms: a randomized crossover trial, Bunker et al

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DHagen

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Bunker, T., Horne, B.D., Baldwin, M.D. et al. Intermittent fasting and a no-sugar diet for Long COVID symptoms: a randomized crossover trial. Sci Rep 15, 27563 (2025). https://doi.org/10.1038/s41598-025-07461-0​

Abstract​

Long COVID (LC) is a common chronic health condition that impairs daily functioning and social connections. This is the first randomized clinical trial to directly compare the effect of two Intermittent Fasting regimens on LC symptoms. The main objectives of this 10-week randomized cross-over trial are to compare the efficacy and safety of 4 weeks of 1–2 day fasting plus a restricted diet vs 4 weeks of mild time-restricted eating (TRE) and a restricted diet in reducing patient-reported LC symptoms. After a 2-week run-in, subjects were randomized to treatment A (TRE) or treatment B (Fasting) for 4 weeks. Subjects then crossed over to the other treatment for 4 weeks. The median fasting duration was 38 h (night-day-night), and the mean duration was 42 h. Symptoms were assessed via weekly online surveys. Primary outcomes were changes in LC symptom severity scores (LC-Scores) and in the number of LC symptoms (numLCsym) between treatments. Secondary outcomes were changes in LC-Scores and numLCsym over the 10-week trial. Fasting was superior to TRE alone in reducing LC-Scores (p = 0.008). The numLCsym decreased − 5.0 during the Fasting 4 weeks vs − 1.4 in the TRE 4 weeks (p = 0.002). Altogether, the 10-week regimen of a no-sugar diet, TRE and Fasting decreased the mean LC-Score by 51.8% (p < 0.0001) from 37.8 to 18.2. Similarly, numLCsym decreased from 20.5 to 12.2, a decrease of 40.6% (p < 0.0001). No major adverse safety events were recorded. Both intermittent fasting interventions decreased symptoms over the 10-week trial but the more intense fasting regimen was significantly better.

https://www.nature.com/articles/s41598-025-07461-0#Sec2
 
Between November 2022 and April 2024, a total of 424 individuals were prescreened via pragmatic electronic means. Of these, 105 proceeded to screening and enrollment (Fig. 1) via video interview and consenting. A total of 96 participants enrolled in the study, however, 19 (20%) of these did not actually begin the study baseline. The “attempted treatment” sample consisted of 77 participants, of whom 58 participants (75%) successfully completed the 10-week study as designed and, thus, comprised the analytic sample.
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Substantial dropout of 25 %, of what’s already a very narrow pool of participants compared to the amount they screened.
 
No correlation at all between the number of hours fasted and the change in LC-Score:
IMG_0276.jpeg
Per simple linear regression, no correlation was found between total fasting duration and decrease in the fasting 4-week LC-Scores as shown by the horizontal green line. The dotted green lines indicate the 95% confidence interval. Participants were able to aim for a 36 hour or 60 hour fast duration each week although they could end their fast at any time. The majority opted for night-day-night fasts of about 38 hours. Note the wide range of changes in LC-Scores for those that did four 38 hour fasts for a total of 152 hours fasting. 56 participants did all four fasts while 2 participants did three fasts. Overall, the median fasting duration was 38.0 hours (night-day-night) and the mean duration was 42.0 hours.
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For what it’s worth, I had little choice but to follow a no sugar diet for quite a while, and I don’t think it had any effect on my ME really. perhaps it meant I was less afraid of my teeth going bad due to inability to brush whilst extremely severe, but apart from that, I think it just took away a small source of joy.
 
I lost the ability to eat for quite a while, then I was on a liquid diet and protein shakes for many months, in all I would say I fasted for about 9 months after I caught Covid and was made very severe, I lost about 30KG. Then I ended up on an extremely restricted FODMAP diet as I responded very poorly to most foods and had to fast on a regular basis due to the constipation or it was life threatening compaction. Thankfully I can now eat a lot more widely but I have still done fasts quite often because I feel mild improvements on them while I do them and they help control weight, but there is no lasting improvement from it on my disease.

The fact 25% dropped out really says a lot about the potential for decline from this intervention and you can feel really rotten doing it.
 
I think it is also worth noting that, even in the rosy interpretation of the results offered by the paper, among the symptoms that were LEAST likely to see any improvement were those core to ME - fatigue and PEM.

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For what it's worth, I am currently no-sugar myself trying to deal with what appears to be recently developed reactive hypoglycemia. Not enjoying it.

[Edited to include image]
 
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