Does fasting during Ramadan alter body composition, blood constituents and physical performance?

Med Princ Pract. 2002;11 Suppl 2:41-6. doi: 10.1159/000066413.


Objective: To study the effect of Ramadan fast (RF) on body composition, plasma constituents, hematology, and cardiorespiratory responses to constant submaximal exercise.

Subjects and methods: Sixteen sedentary healthy Kuwaiti adult males were included in the study. The subjects were tested under thermo-neutral conditions during a spring-like month of Ramadan and 2 months thereafter. They were tested during the week before RF (Pre1); the last 3 days of RF (End1); the week before a non-Ramadan month (Pre2), and the last 3 days of the non-Ramadan month (End2). The following measurements were made: body composition, cellular and biochemical constituents of blood, heart rate, ventilatory responses and blood pressure.

Results: No significant changes were observed in body composition, cellular and biochemical constituents of blood. The heart rate and ventilatory responses to the moderately intense bouts of submaximal aerobic exercise ( approximately 70% of VO(2max)) were significantly reduced (p < 0.04) while systolic blood pressure increased (p < 0.05) by the end of RF.

Conclusions: Ramadan fasting had no adverse effect on the subjects when performing aerobic exercise at submaximal level. The mild changes in cardiorespiratory responses could be due to dehydration, abstention from consumption of substances with negative inotropy and circadian rhythms.

MeSH terms

  • Adult
  • Analysis of Variance
  • Blood Chemical Analysis
  • Body Composition*
  • Dehydration / metabolism
  • Dehydration / physiopathology
  • Exercise Tolerance / physiology
  • Fasting / metabolism
  • Fasting / physiology*
  • Heart Rate / physiology
  • Humans
  • Islam*
  • Male
  • Oxygen Consumption / physiology
  • Pulmonary Ventilation / physiology