During the month of Ramadan, many Muslims worldwide observe fasting from dawn to sunset. This period involves abstaining from food, drink, and other physical needs as a form of worship and self-discipline.
Dr. Sherif Hassan, a professor of internal medicine at the UC Riverside School of Medicine, addressed several questions about the medical aspects of Ramadan fasting. Dr. Hassan has extensive experience in medical education and training.
He explained that “Fasting during Ramadan is physiologically similar to time-restricted eating, as both shift the body from glucose to fat use after 12–16 hours. The key difference is that Ramadan prohibits fluids during daylight hours, increasing dehydration risk. Sleep pattern changes during Ramadan can also influence metabolic outcomes.”
Describing what happens in the body during prolonged fasting, Dr. Hassan said: “After glycogen stores decline, insulin falls and the body increases fat breakdown and mild ketone production. Growth hormones rise and insulin sensitivity may improve temporarily. Energy shifts from glucose dependence to greater fat utilization.”
Short-term improvements in blood sugar levels, insulin sensitivity, triglycerides, and HDL cholesterol are often observed with fasting according to Dr. Hassan: “Short-term improvements in glucose, insulin sensitivity, triglycerides, and HDL are commonly observed. Effects depend heavily on diet quality and calorie intake during eating windows. Benefits often reverse if prior eating habits resume.”
When asked whether health benefits differ for men and women he noted: “Women may be more hormonally sensitive to prolonged calorie restriction, particularly if underweight or stressed. Some may experience menstrual irregularities with aggressive fasting. Healthy men and women generally tolerate Ramadan well, but individual variability is significant.”
For people with type 2 diabetes considering fasting during Ramadan he advised caution: “People with type 2 diabetes can fast safely only if well controlled and medically supervised. Medication timing must be adjusted and glucose monitored closely. High-risk patients (those with poor diabetes control, insulin dependence, or kidney disease) are usually advised not to fast.”
Regarding cardiovascular effects Dr. Hassan stated: “Modest reductions in blood pressure and improvements in lipid markers are often seen. Weight loss and improved insulin sensitivity likely drive these effects. Dehydration, however, can cause dizziness or blood pressure fluctuations.”
On weight loss he remarked: “Weight loss during Ramadan is typically modest and often temporary. Long-term success depends on sustained calorie control and healthy food choices. Fasting itself is a tool, not a guarantee of fat loss.”
He discussed risks for those with heart conditions: “Stable cardiac patients may fast safely with physician guidance. Those with advanced heart failure, unstable angina, or significant arrhythmias face higher risks from dehydration and electrolyte imbalance. Individual risk assessment is essential.”
Addressing mental clarity he commented: “Some people report improved alertness due to mild ketosis and catecholamine increases. Others experience fatigue or reduced concentration, especially with dehydration or poor sleep. Cognitive response varies widely by individual.”
Concerning exercise while fasting he suggested moderation: “Light to moderate exercise is generally safe, especially near or after breaking the fast. Intense training during prolonged dehydration increases risk of heat illness and fatigue. Athletes should optimize nighttime hydration and adjust training loads.”
Dr. Hassan advised against fasting for pregnant women: “Pregnant women are generally advised not to fast.” He added that breastfeeding could be affected by hydration status while frail elderly individuals have higher risks related to dehydration.
On who should avoid fasting for medical reasons he was clear: “Those with uncontrolled diabetes, advanced kidney or heart disease, severe liver disease, eating disorders, or acute illness should not fast without medical clearance.” He noted that high risk of hypoglycemia or dehydration outweighs potential benefits.
Reviewing current research on long-term health effects he said: “Evidence shows short-term metabolic improvements but limited proof of lasting change without continued lifestyle modification.” He found no strong evidence suggesting harm among healthy adults.
Finally Dr.Hassan indicated that overweight individuals or those improving their diets might see more benefit than others: “Overweight individuals and those with mild insulin resistance often see the most metabolic improvement…Lean metabolically healthy individuals may see minimal measurable change.”
