Ramadan Fasting Changes Sleep Architecture and Increases Daytime Sleepiness: What the Research Shows

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

Study at a Glance

What This Study Looked At

Researchers wanted to know what happens to actual sleep structure — not just self-reported tiredness — when people fast from dawn to dusk every day for a month, as practiced during Ramadan. This is a form of intermittent fasting, though the daily fasting window is longer and shifted compared to typical 16:8 or OMAD schedules. The team used overnight polysomnography and daytime testing to see whether dawn-to-dusk fasting changed sleep stages and next-day alertness compared to a non-fasting baseline.

Who Was Studied

Participant profile: Healthy young adult male students, non-smokers, with no diagnosed sleep disorders at baseline.

How the fasting protocol worked in this study: Participants abstained from all food and drink, including water, from dawn until sunset each day throughout the month of Ramadan — a longer and differently timed fasting window than a typical intermittent fasting schedule, but a dawn-to-dusk fast nonetheless. Sleep and wake times followed each participant's normal daily schedule, including the pre-dawn meal (suhoor) and the after-sunset meal (iftar).

What the Researchers Found

Sleep Architecture Changes

• Total time asleep at night stayed broadly similar between the two periods, meaning participants weren't simply sleeping less overall.
• The proportion of REM sleep dropped during the fasting month, suggesting fasting altered sleep quality even when quantity was maintained.
• Sleep became harder to initiate and more fragmented during Ramadan compared to baseline.

Daytime Sleepiness

• On the multiple sleep latency test (a standard lab measure of how quickly someone falls asleep during the day), sleep latency was shorter during Ramadan — meaning participants fell asleep faster during the day, a marker of increased daytime sleepiness.
• Subjective sleepiness ratings during waking hours also increased compared to the non-fasting baseline.
• The waking EEG showed changes consistent with reduced alertness in the afternoon hours specifically, which lines up with the period furthest from the pre-dawn meal.

What Did Not Change

• Overall nightly sleep duration remained broadly comparable between fasting and non-fasting periods.
• No evidence of a serious sleep disorder emerging from the fasting period — the changes were shifts in sleep quality and daytime alertness, not a breakdown of sleep entirely.

What the Researchers Concluded

The authors concluded that dawn-to-dusk Ramadan fasting altered sleep architecture — particularly REM sleep and sleep continuity — and increased objectively measured daytime sleepiness, even though total nightly sleep time was largely preserved.

What This Means If You Fast

• Extended or shifted fasting windows can affect sleep quality, not just quantity. If you notice more fragmented sleep or daytime grogginess on longer fasting protocols, this study suggests it's a real, measurable phenomenon rather than something in your head.
• Meal timing close to sleep may matter. Because participants ate before dawn and after sunset, shifted meal timing likely interacts with the body's circadian rhythm, similar to what's discussed in what happens to your body during intermittent fasting.
• Daytime sleepiness during a fasting month is common and expected, not necessarily a red flag. Planning lighter cognitive or physical demands into the early afternoon during extended fasting periods may help.
• Standard daily intermittent fasting (16:8, OMAD) is a different pattern than a month-long dawn-to-dusk fast and may not produce identical sleep effects, since eating and sleep timing aren't shifted to the same degree.
• If sleep problems persist beyond an adjustment period, it's worth addressing food quality and pre-sleep meal timing, consistent with general guidance in does intermittent fasting affect sleep.

Study Limitations

• Very small sample size (n=8), all young adult male students — findings may not generalize to women, older adults, or other populations.
• Within-subject design without an independent, weather-matched control group fasting on a normal schedule.
• Ramadan fasting differs from typical intermittent fasting in duration, timing, and cultural/social context (nighttime eating, altered sleep schedules), limiting direct comparison to standard 16:8 or OMAD protocols.
• Short duration relative to long-term sleep health outcomes — the study captures changes during a single fasting month only.
• Because of network restrictions at the time of writing, this summary was written from general knowledge of the published literature rather than a live re-read of the original abstract; exact statistical values (p-values, percentage changes) were not independently re-verified against the source and should be treated as approximate.

Source

Roky, R., Chapotot, F., Benchekroun, M. T., Benaji, B., Hakkou, F., Elkhalifa, M. H. F., & Buguet, A. (2001). Daytime sleepiness during Ramadan intermittent fasting: polysomnographic and quantitative waking EEG study. Journal of Sleep Research, 10(4), 319–327. Search on PubMed →

Frequently Asked Questions

Does intermittent fasting reduce REM sleep?

This particular study on Ramadan-style dawn-to-dusk fasting found a reduction in REM sleep proportion during the fasting period compared to a non-fasting baseline, though total sleep time was largely preserved.

Does fasting cause daytime sleepiness?

In this study, objectively measured daytime sleep latency shortened during Ramadan fasting, indicating increased daytime sleepiness compared to the non-fasting baseline period.

Is Ramadan fasting the same as intermittent fasting for sleep research purposes?

Not exactly. Ramadan fasting involves a longer daily fasting window, shifted meal timing (pre-dawn and after-sunset meals), and altered sleep schedules, which makes its effects on sleep somewhat different from a standard 16:8 or OMAD protocol.

Does 16:8 intermittent fasting affect sleep the same way as this study found?

This study did not test 16:8 fasting specifically, so its findings shouldn't be directly extrapolated to shorter daily fasting windows without further research.

Should I worry if I feel sleepier during a fasting period?

Based on this research, some increase in daytime sleepiness during an extended or shifted fasting schedule appears to be common. Persistent or severe sleep problems are still worth discussing with a healthcare provider.

Related Research and Articles

• Does intermittent fasting affect sleep?
• What happens to your body during intermittent fasting?
• Intermittent fasting and sleep quality in women
• What happens to your body hour by hour when you fast
• Electrolytes and intermittent fasting

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