The science of Ramadan fasting

Dr. Sherif Hassan

Does Ramadan fasting come with medical benefits? How does it compare to intermittent fasting and what happens in the body during 12-16+ hours without food? How can athletes fast safely? Are there risks and precautions for people with type 2 diabetes, those with heart conditions, pregnant or breastfeeding women, the elderly, and others who may be medically vulnerable?

Dr. Sherif Hassan, a professor of internal medicine at the UC Riverside School of Medicine, answers these and other questions about fasting. He earned his medical degree and doctorate from Cairo University, Egypt, and completed residency training in general medicine, surgery, and clinical and chemical pathology. He has decades of experience in medical education, including anatomy, neuroanatomy, medical imaging, and embryology.

Q. How does Ramadan fasting compare to intermittent fasting from a medical perspective?

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.

Q. What happens in the body during a fast of 12-16+ hours?

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.

Q. Does fasting improve metabolic health (blood sugar, insulin sensitivity, cholesterol)?

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.

Q. Are the health benefits different for men and women?

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.

Q. Is Ramadan fasting safe for people with type 2 diabetes?

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.

Q. Does fasting lower blood pressure or improve cardiovascular health?

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.

Q. Can fasting help with weight loss in a sustainable way?

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.

Q. Are there risks for people 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.

Q. Does fasting improve mental clarity or focus?

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.

Q. Is it safe to exercise while fasting?

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.

Q. Should pregnant or breastfeeding women fast? What about elderly individuals?

Pregnant women are generally advised not to fast. Breastfeeding may be affected by hydration and calorie intake. Frail elderly individuals are at higher risk of dehydration, falls, and kidney stress.

Q. Who medically should not fast, even if they want to?

Those with uncontrolled diabetes, advanced kidney or heart disease, severe liver disease, eating disorders, or acute illness should not fast without medical clearance. High risk of hypoglycemia or dehydration is a major contraindication. Medical harm outweighs potential benefits in these groups.

Q. What does current medical research say about the long-term health effects of Ramadan fasting?

Evidence shows short-term metabolic improvements but limited proof of lasting change without continued lifestyle modification. No strong evidence suggests harm in healthy adults. Long-term benefits depend on sustained healthy behaviors.

Q. Are there groups of people who benefit more than others from fasting?

Overweight individuals and those with mild insulin resistance often see the most metabolic improvement. People who improve diet quality during Ramadan benefit more than those who overconsume high-calorie foods. Lean, metabolically healthy individuals may see minimal measurable change.