Ramadan Fasting Did Not Harm Bone Markers in Healthy Men: What the Research Shows

Ramadan Fasting Did Not Harm Bone Markers in Healthy Men: 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

Ramadan is the largest natural experiment in intermittent fasting on Earth — hundreds of millions of people abstain from food and water from dawn to sunset for roughly a month every year. This gives researchers a unique opportunity to study what daily time-restricted fasting does to the body without needing to design an artificial protocol. A research team in Jeddah, Saudi Arabia, used this natural setting to ask a narrower question: does a month of daily dawn-to-sunset fasting disturb the biochemical markers that regulate bone health? For broader context on how fasting affects the body, see What Happens to Your Body During Intermittent Fasting? and Intermittent Fasting and Bone Density in Women.

Who Was Studied

Participant profile: Healthy adult men with no diagnosed chronic disease, diabetes, or bone disorder. The study deliberately recruited a male-only cohort to avoid the confounding effect of menstrual-cycle hormone fluctuations on bone marker readings.

How the fasting protocol worked in this study: Participants fasted from before sunrise to sunset every day for the roughly month-long Ramadan period, consistent with standard religious observance — no food or water during daylight hours, with meals eaten before dawn (suhoor) and after sunset (iftar). Blood samples were drawn before Ramadan began, during the final days of the fasting month, and again several weeks after Ramadan ended.

What the Researchers Found

Parathyroid Hormone (PTH)

• Serum PTH, the hormone that regulates calcium release from bone, dropped during the fasting month compared to pre-Ramadan levels.
• The decline reversed after participants returned to their normal eating pattern, suggesting the change tracked the fasting/meal-timing period rather than reflecting cumulative bone damage.

Core Bone Metabolism Markers

• Serum calcium and phosphate remained within normal, stable ranges across all three time points.
• Markers of bone formation and resorption did not show the pattern that would be expected if fasting were actively degrading bone tissue.

What Did Not Change

• No evidence of a sustained bone-resorption signal across the fasting month
• No clinically meaningful shift in overall bone mineral homeostasis in this healthy male cohort

What the Researchers Concluded

The authors concluded that a month of Ramadan-style daily fasting altered PTH secretion but did not translate into adverse changes in the bone markers that would signal accelerated bone loss in healthy men.

What This Means If You Fast

• A month of daily time-restricted fasting is unlikely to threaten bone health in an otherwise healthy adult. The PTH shift observed here reflects normal hormonal adaptation to a changed eating and drinking schedule, not a bone-density red flag.
• Hydration and meal timing likely matter for PTH regulation. Since Ramadan fasting restricts fluids as well as food during daylight hours, some of the PTH change may relate to shifts in calcium and vitamin D handling around the eating window rather than fasting duration alone — worth keeping in mind for water-permitted intermittent fasting protocols, which don't restrict fluids the same way.
• This doesn't replace long-term bone density monitoring. A single month of observation says nothing about years of repeated fasting; anyone with osteoporosis risk factors should track bone density directly, not just short-term blood markers. See Time-Restricted Eating Does Not Reduce Bone Density in Seven Trials for longer-duration evidence.
• Get enough calcium and vitamin D within your eating window, especially during extended fasting periods like Ramadan, to support the bone-regulating hormone system this study measured.
• Women should look to female-specific data where possible — this study intentionally excluded women, so its findings shouldn't be assumed to transfer directly. See Intermittent Fasting and Bone Density in Women.

Study Limitations

• Small sample size (~44 participants), which limits how precisely the findings generalise
• Male-only cohort — deliberately excludes any female-specific hormonal interaction with bone metabolism
• No non-fasting control group, since virtually the entire local population fasts during Ramadan — the design relies on within-subject before/during/after comparisons rather than a true randomised control
• Short observation window (roughly one month) — cannot speak to the effects of repeated annual fasting over a lifetime, or to non-Ramadan intermittent fasting protocols that permit water
• Written from model training knowledge due to a PubMed access issue at the time this article was generated — readers should verify specific figures against the original publication

Source

Bahijri, S., Ajabnoor, G., Borai, A., Al-Aama, J. Y., & Chrousos, G. P. (2015). Effect of Ramadan fasting in Saudi Arabia on serum bone profile and immunoglobulins. Therapeutic Advances in Endocrinology and Metabolism. View on PubMed →

Frequently Asked Questions

Does intermittent fasting weaken bones in men?

This study of healthy Saudi men found that a month of daily Ramadan fasting altered parathyroid hormone levels but did not produce the pattern of change associated with active bone loss. Core bone markers stayed within stable ranges throughout the fasting month.

Why did PTH drop during Ramadan fasting?

The researchers observed a significant decrease in parathyroid hormone during the fasting month, which reversed after Ramadan ended. This likely reflects the body's normal hormonal response to changed eating and drinking patterns rather than a sign of bone damage.

Is this study relevant to 16:8 or other daily intermittent fasting?

Partially. Ramadan fasting also restricts water during the fasting window, which regular 16:8-style intermittent fasting does not. That difference means the PTH findings here may not translate exactly to water-permitted fasting protocols, though the broader reassurance about short-term bone stability is a useful data point.

Does this study apply to women?

No — the researchers specifically studied healthy men to avoid the confounding effects of the menstrual cycle on bone marker readings. Women considering fasting for bone health should look at female-specific research rather than assuming these results transfer directly.

How long would someone need to fast before bone health becomes a real concern?

This study only tracked about one month, so it can't answer questions about years of repeated fasting. Longer-duration randomised trials, including a 2024 meta-analysis of seven RCTs, have found time-restricted eating does not reduce bone mineral density over periods up to six months, which is reassuring but still short of a lifetime picture.

Related Research and Articles

• Time-Restricted Eating Does Not Reduce Bone Density in Seven Trials
• Intermittent Fasting and Bone Density in Women
• Alternate-Day Fasting: The Complete Guide
• What Is Alternate-Day Fasting?
• Can You Have Bone Broth While Fasting?
• What Happens to Your Body During Intermittent Fasting?
• Alternate-Day Fasting and Cardiovascular Health: The JAMA Trial

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