Fasting (langhana, religious fasts)

Practical note

Graded low: the evidence is a meta-analysis of 66 observational before-after studies (7611 participants), pooled weight change about 1.1 kg with no comparison group; an umbrella review rated the methodological quality of the existing Ramadan meta-analyses low to critically low. The consistency of the direction keeps it from very low.

Sources

• Supports“RIF is associated with a reduction in body weight, BMI, WC, HC, FM, FP and TBW. Most of these reductions are partially attributed to reduced FM and TBW. The reductions in these parameters appear to reverse after Ramadan.” (Abstract, Conclusion) Al-Jafar R, Wahyuni NS, Belhaj K, Ersi MH, Boroghani Z, Alreshidi A, Alkhalaf Z, Elliott P, Tsilidis KK, Dehghan A. 2023. Frontiers in Nutrition. The impact of Ramadan intermittent fasting on anthropometric measurements and body composition: Evidence from LORANS study and a meta-analysis. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Context“Nevertheless, the methodological quality of the included reviews ranged from low to critically low, necessitating cautious interpretation of conclusions drawn from these data.” (Abstract, Conclusion) Jahrami H, Ammar A, Glenn JM, Saif Z, Chtourou H, Trabelsi K. 2025. Nutrition Reviews. An umbrella review and meta-analysis of meta-analyses of the impact of Ramadan fasting on the metabolic syndrome components. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

Practical note

Graded low: a meta-analysis of 33 observational before-after studies (3213 participants) found systolic pressure about 3 mm Hg and diastolic about 2 mm Hg lower, with moderate heterogeneity; no lower pressures were seen in the subgroup with chronic kidney disease. An umbrella review of 11 meta-analyses found the same direction but rated their quality low to critically low.

Sources

• Supports“Ramadan fasting appears to benefit body weight, lipid profile, blood pressure, and fasting blood glucose levels.” (Abstract, Conclusion) Jahrami H, Ammar A, Glenn JM, Saif Z, Chtourou H, Trabelsi K. 2025. Nutrition Reviews. An umbrella review and meta-analysis of meta-analyses of the impact of Ramadan fasting on the metabolic syndrome components. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Supports“SBP and DBP after/before Ramadan were lower by 3.19 mm Hg (-4.43 to -1.96, I2=48%) and 2.26 mm Hg (-3.19 to -1.34, I2=66%), respectively.” (Abstract, Methods and Results) Al-Jafar R, Zografou Themeli M, Zaman S, Akbar S, Lhoste V, Khamliche A, Elliott P, Tsilidis KK, Dehghan A. 2021. Journal of the American Heart Association. Effect of Religious Fasting in Ramadan on Blood Pressure: Results From LORANS (London Ramadan Study) and a Meta-Analysis. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

Practical note

Based on a 2025 network meta-analysis of 99 randomised trials (6582 adults) that applied GRADE; only alternate day fasting outperformed continuous restriction, by about 1.3 kg in shorter trials, and trials of 24 weeks or more showed no difference between strategies. Religious fasts differ from these research diets in timing and duration, so the link is indirect.

Safety note

A meta-analysis of 15 randomised trials in adults with overweight found no higher rate of fatigue, headache or dropout with intermittent fasting, with a non-significant signal for more dizziness in one subgroup.

Sources

• Supports“The current evidence provides some indication that intermittent fasting diets have similar benefits to continuous energy restriction for weight loss and cardiometabolic risk factors.” (Abstract, Conclusions) Semnani-Azad Z, Khan TA, Chiavaroli L, Chen V, Bhatt HA, Chen A, Chiang N, Oguntala J, Kabisch S, Lau DC, Wharton S, Sharma AM, Harris L, Leiter LA, Hill JO, Hu FB, Lean ME, Kahleova H, Rahelic D, Salas-Salvado J, Kendall CW, Sievenpiper JL. 2025. BMJ. Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials. publisher copyright; metadata and short quotes only
• Context“This meta-analysis suggested that IF was not associated with a greater risk of AEs in adult patients affected by overweight or obesity.” (Abstract, Conclusions) Zhong F, Zhu T, Jin X, Chen X, Wu R, Shao L, Wang S. 2024. Nutrition Journal. Adverse events profile associated with intermittent fasting in adults with overweight or obesity: a systematic review and meta-analysis of randomized controlled trials. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

Practical note

Graded low: this rests on a consensus practice guideline (IDF and DaR International Alliance, 2021) rather than pooled trial outcomes.

Sources

• Supports“Though individuals with some illness and serious medical conditions, including some people with diabetes, can be exempted from fasting, many will fast anyway.” (Abstract) Hassanein M, Afandi B, Yakoob Ahmedani M, et al. (IDF and DaR International Alliance). 2022. Diabetes Research and Clinical Practice. Diabetes and Ramadan: Practical guidelines 2021. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Context“Exceptions from Islamic recommendations are those who are ill, elderly, children, pregnant or breastfeeding women or those traveling.” (Islam) Maslov PZ, Sabharwal B, Ahmadi A, Baliga R, Narula J. 2022. Indian Heart Journal. Religious fasting and the vascular health. CC BY-NC-ND 4.0; credit Maslov et al., Indian Heart Journal 2022

Practical note

In the cited Ayurvedic study, upavasa was applied as reduced-quantity eating with portions gradually increased, rather than total abstinence from food.

Vegan note

Ayurvedic fasting is usually plant-based (light meals, fruit, water or broths), which fits a vegan diet.

Sources

• Supports“Ayurveda claims Langhanam param aushadham, or that fasting is the best medicine.” (History of fasting) Maslov PZ, Sabharwal B, Ahmadi A, Baliga R, Narula J. 2022. Indian Heart Journal. Religious fasting and the vascular health. CC BY-NC-ND 4.0; credit Maslov et al., Indian Heart Journal 2022
• Supports“Langhana is the prime tool in the process of Dhatusamya.” (Abstract) Rajani A, Vyas MK, Vyas HA. 2010. Ayu. Comparative study of Upavasa and Upavasa with Pachana in the management of Agnisada. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine