Physiological and chronobiological changes during Ramadan intermittent fasting

Ann Nutr Metab. 2004;48(4):296-303. doi: 10.1159/000081076. Epub 2004 Sep 24.


Background and aims: During the month of Ramadan, Moslems refrain from drinking and eating between sunrise and sunset. This review aimed to analyze the effects of Ramadan fasting on physiological and behavioral variables in healthy subjects.

Methods: Articles included in this paper were taken from Medline, three international congresses on health and Ramadan, and in several cases from local journals.

Results: Ramadan fasting did not dramatically affect the metabolism of lipids, carbohydrates and proteins, or the daily mean of hormonal serum levels. An increase in serum urea and uric acid was frequently reported and this could be attributed to dehydration during this month. Some changes, such as the increase of HDL and apoprotein A1, and the decrease in LDL, could be beneficial for the cardiovascular system. However, the chronobiological studies have shown that Ramadan fasting affects the circadian distribution of body temperature, cortisol, melatonin and glycemia. The amplitude of most of these rhythms decreased and the acrophase shifted. Nocturnal sleep, daytime alertness and psychomotor performance were decreased.

Conclusion: The major changes during Ramadan fasting are chronobiological and behavioral. They could be responsible for the high incidence of road traffic accidents and the reduction of working hours during the month of Ramadan.

Publication types

  • Review

MeSH terms

  • Accidents, Traffic
  • Affect
  • Arousal / physiology
  • Behavior / physiology
  • Circadian Rhythm
  • Fasting / blood
  • Fasting / physiology*
  • Hormones / blood
  • Humans
  • Islam*
  • Lipids / blood
  • Psychomotor Performance
  • Time Factors


  • Hormones
  • Lipids