Episode 189: Intermittent Fasting (Religious and Sports)
Future Doctors Carlisle and Kim give recommendations about patients who are fasting for religious reasons, such as Ramadan. They also explain the benefits and risks of fasting for athletes and also debunked some myths about fasting. Dr. Arreaza add input about the side effects of fasting and ways to address them.
Written by Cameron Carlisle, MSIV (RUSM) and Kyung Kim, MSIV (AUC). Editing by Hector Arreaza, MD.
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Introduction:
In the last episode on fasting (#179), we explored how intermittent fasting (IF) can help manage type 2 diabetes by improving insulin sensitivity, promoting weight loss, and lowering inflammation. We discussed the benefits of methods like 16:8 time-restricted eating and the 5:2 meal plan, and even compared IF to medications like metformin. Today, we’re bringing that science into real life. We’ll talk about how people fast for religious reasons, like during Ramadan, how athletes use IF to stay in shape, and how we can use IF as a tool in family medicine to support community health and A1c control.
Intermittent Fasting in Religious Practice
Ramadan just ended on 3/30/25, but this is a great time to talk about the broader role of fasting in religion and health. Many faiths incorporate fasting into spiritual practice and understanding this can help us better support our patients.
Islam (Ramadan): Ramadan is a month where Muslims fast from dawn to sunset, focusing on spiritual reflection and self-control. No food or drink is consumed during daylight hours. Despite this, studies have shown that with good planning, fasting during Ramadan does not significantly impair physical performance or metabolic health.
Key health tips for patients observing Ramadan:
- Hydrate well between iftar (sunset) and suhoor (pre-dawn).
- Break the fast with dates and water to gently replenish energy and electrolytes.
- Eat balanced meals with complex carbs, protein, and healthy fats
- Avoid greasy, heavy foods right after fasting
- Light exercise (such as a walk) after iftar is beneficial
- Review medications with a healthcare provider, especially for those on insulin or sulfonylureas.
For example: Metformin should be taken when you break your fast and then again before dawn. If its an extended-release metformin, take it at night. Metformin does not cause significant hypoglycemia and can be continued during Ramadan. Basal insulin is advised to be given at Iftar, and the dose should be reduced by 25-35% if the patient is not well managed. And regarding the fast-acting insulin, it requires a little more reading, so you can look it up and learn about it.
Judaism: In Judaism, fasting is practiced on days like Yom Kippur and Tisha B’Av, typically lasting 25 hours without food or water. These fasts are spiritual and reflective, and patients with medical conditions may seek guidance on how to participate safely.
Christianity: Many Christians fast during Lent, either by abstaining from certain foods or limiting meal frequency. Some practice partial-day fasts or water-only fasts for spiritual renewal.A branch of Christianity known as The Church of Jesus Christ of Latter-day Saintsoften observe a 24-hour fast on the first Sunday of each month, known as Fast Sunday, where they abstain from food and drink and donate the cost of meals to charity. This practice is both spiritual and communal.
Cameron: Fasting for religious reasons, when done safely, can align with IF protocols and be culturally sensitive for diverse patients in family medicine.
IF in Athletes and Performance
Intermittent fasting is gaining popularity in the sports world. Athletes are using IF to improve body composition, increase fat oxidation, and enhance metabolic flexibility. A recent study, known as the DRIFT trial and published in Annals of Internal Medicine, found that fasting three non-consecutive days a week led to more weight loss than daily calorie restriction. Participants lost an average of 6.37 pounds more over 12 months.
Why? Better adherence. People found the 3-day fasting schedule easier to stick to than counting calories every day.
Benefits of IF for athletes:
- Encourages fat burning (via AMPK activation and GLUT4 upregulation, listen to ep. 179).
- Helps maintain lean muscle while reducing fat.
- No major drop in performance when meals and workouts are timed properly.
What are some practical tips?
- Schedule workouts during or just before eating windows.
- Eat protein-rich meals post-workout.
- Avoid intense training during long fasts unless adapted.
- Stay hydrated, especially in hot environments or endurance sports.
Broader Applications and Myths Around IF
Hormonal Effects of IF: In addition to improving insulin sensitivity, IF also affects hormones such as ghrelin (which stimulates hunger, remember it as growling) and leptin (which signals fullness). Over time, IF may help the body regulate appetite better and reduce cravings. IF can also decrease morning cortisol levels, the stress hormone. That’s why it's important to monitor sleep, hydration, and stress levels when recommending IF.
Circadian Rhythm Alignment:
Emerging research shows that aligning eating times with natural light/dark cycles—eating during the day and fasting at night—can improve metabolic outcomes. This practice, known as early time-restricted eating (eTRE), has been shown to lower blood glucose, reduce insulin levels, and improve energy use. Patients who eat earlier in the day tend to have better results than those who eat late at night.
Myths and Clarifications on IF:
-“Fasting slows metabolism” In fact, short-term fasting may boost metabolism slightly due to increased norepinephrine.
-“You can’t exercise while fasting.” Many people can safely train during fasted states, especially for moderate cardio or strength training.
-“Skipping breakfast is bad.” For some, skipping breakfast is a useful IF strategy—as long as total nutrition is maintained. You can break your fast at 2:00 pm, it does have to be at 7:00 AM.
What to Eat When Breaking a Fast
Breaking a fast properly is just as important as fasting itself. Whether it’s after a Ramadan fast or a 16-hour fast, the goal is to replenish energy gently and restore nutrients.
Ideal foods to break a fast:
- Dates and water: provide quick energy, potassium, and fiber
- Soups: lentil or broth-based soups are gentle on digestion
- Complex carbs: whole grains like brown rice or oats
- Lean proteins: chicken, fish, eggs, legumes
- Fruits and vegetables: hydrate and provide fiber
- Healthy fats: nuts, avocado, olive oil
- Probiotics: yogurt or kefir for gut support
Balanced meals with carbs, protein, and healthy fats help the body transition smoothly back to a fed state.
Using IF in Family Medicine and Community Health
Intermittent fasting can be a practical, cost-effective strategy in family medicine. In areas with high rates of obesity and diabetes, like Kern County, IF offers a lifestyle-based tool to improve metabolic health, especially in underserved populations. IF is free!
How IF can help in family medicine:
- Lower A1c levels: improves insulin sensitivity and glucose control
- Promote weight loss: decreases insulin resistance and inflammation
- Reduce medication dependence: fewer meds needed over time for some patients
- Encourage patient engagement: flexible and easier to follow than strict calorie counting
- Fit diverse lifestyles: aligns with religious and cultural practices
- Address food insecurity: structured eating windows can help patients stretch limited food resources
How to apply IF in clinic:
- Start the conversation by asking if the patient has heard of IF
- Recommend simple starting points: 12:12 or 14:10
- Emphasize hydration and nutrient-dense meals
- Monitor labs and symptoms, especially in diabetic patients
- Adjust medications to avoid hypoglycemia
- Provide follow-up and patient education handouts if possible
What if a patient isn't ready to try fasting?
- For those not ready to commit to intermittent fasting, one effective alternative is walking after meals. A simple 10–20 minute walk post-meal can help stimulate GLUT4 receptors in skeletal muscle, promoting glucose uptake independent of insulin. This reduces the demand on pancreatic beta cells and may help improve blood sugar control over time. This strategy is particularly useful for patients with insulin resistance or early-stage type 2 diabetes.
Conclusion:
Intermittent fasting is not one-size-fits-all, but it can be a powerful tool for both individual and community health. From Ramadan to race day, IF has a place in family medicine when used thoughtfully. Encourage patients to work with their healthcare providers to find an approach that fits their lifestyle, medical needs, and personal values. IF is a cost-effective tool
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References:
- American Academy of Family Physicians. (2022). "Intermittent Fasting: A Promising Treatment for Diabetes." AAFP Community Blog. https://www.aafp.org/pubs/afp/afp-community-blog/entry/intermittent-fasting-a-promising-treatment-for-diabetes.html
- Healthline. (2023). "What Breaks a Fast? Foods, Drinks, and Supplements." https://www.healthline.com/nutrition/what-breaks-a-fast.
- Sarri KO, Tzanakis NE, Linardakis MK, Mamalakis GD, Kafatos AG. Effects of Greek Orthodox Christian Church fasting on serum lipids and obesity. BMC Public Health. 2003 May 16;3:16. doi: 10.1186/1471-2458-3-16. PMID: 12753698; PMCID: PMC156653. https://pmc.ncbi.nlm.nih.gov/articles/PMC156653/.
- Shang, Y., et al. (2024). "Effects of Intermittent Fasting on Obesity-Related Health Outcomes: An Umbrella Review." eClinicalMedicine.https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(24)00098-1.
- Abaïdia AE, Daab W, Bouzid MA. Effects of Ramadan Fasting on Physical Performance: A Systematic Review with Meta-analysis. Sports Med. 2020 May;50(5):1009-1026. doi: 10.1007/s40279-020-01257-0. PMID: 31960369. https://pubmed.ncbi.nlm.nih.gov/31960369/.
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