“Doctor, I want to ask you about fasting on this new medication.  My faith is important to me and I usually fast.”

To be honest, I talk alot about fasting lately since Intermittent Fasting is such a wellness trend (TL;DR – I don’t recommend or prescribe it for non-religious reasons) Since it’s Ramadan and Lent, let’s break down the science!

This above quote, by the way, was not a conversation about Ramadan.  This was a younger Catholic patient reminding me that it is Lent. And it shows how times in Ireland have changed that I hadn’t even thought of counseling a patient of that age to be cautious fasting on their medication.  (Need to keep checking that unconscious bias!)   Even when it’s not Ramadan or Lent, my patients attending for pre-diabetes or obesity often ask about the benefits of intermittent fasting.  It’s the diet that’s trending (remember when it was all keto?  Or Atkins? Or Zone?).  They ask me if I recommend it for health benefits.  I don’t. However, when it comes to religious observances, I do make sure that I give them the correct health advice so that they can make their own decision, or bring that information to their spiritual advisor of choice.

Let’s talk health first. Few things you should know:

1. If you are going to fast to be healthier, you should be happy that you do not any health conditions or medications that require that you eat regularly*. You should have a good relationship with food, and not be stressed or “hangry” while fasting.  The food you eat during hours you not fasting should be healthy: low in processed foods, and meals should include all your recommended intake of protein, fibre, etc.**  You should not heavily restrict food and supplement actual food with commercial supplements. If you break your fast with a binge or thoughts of food are becoming obsessive, this is a sign that you should not be fasting.

Sign you Shouldn't Be Fasting?

I had a patient recently who ate only once a day.   They confessed at the second appointment that they spent all day bookmarking recipes, scrolling through food sites, following food influencers.  They weren’t eating all day but spent hours planning the meal to be eaten later. It had become borderline obsessive.  

2. What health benefit are you looking for? If it is weight loss – the evidence so far is that just intermittent fasting by itself, with no other healthy changes – doesn’t work.  And it certainly is not a stand-alone treatment for the disease of obesity.   At best, just time-restricting food with no other improvements leads to short term loss followed by weight recurrence.

3. Much of the science on intermittent fasting that wellness marketing ads cite was done on animals. If you are a rat, this is great news. Less so if you are a human.  The human studies done to date – which are few – have some flaws.  And the most recent, respected studies suggest that data is still inconclusive.  While intermittent fasting does have benefits for cardiac risk factors in some human studies, so far it seems that these benefits are no better than if someone made different healthy dietary changes, such as carbohydrate controlling or calorie restricting.

4. Intermittent fasting is NOT a good choice for those who struggle with their relationship with food or are at risk or have disordered eating. If you break your fast, do you feel guilty? (you shouldn’t.)

5. For those living with families, also consider the side effects: If you aren’t eating dinner, are you missing connection time with your family?  Are you skipping coffee mornings or catch-up lunches?  If your children notice you not eating meals, what is the dialogue that you are having?   Is it body size/body image or just health?  Many people start to learn diet culture and body image from an early age from their parents.

6. Plain English summary on the Emerging evidence is that those at risk for heart disease should probably avoid intermittent fasting.  You can also read the slightly-more-technical work here.

Mythbusting:  An app’s “personalised intermittent fasting” plan is not your best source of nutrition advice**. You do not need a supplement or support drink or specialised vitamins for intermittent fasting.  You do not need a fasting coach, virtual or otherwise.  The no-cost approach will work just as well if you want to try it. 

What can Ramadan tell us about intermittent fasting?

For the month of Ramadan, around 1 billion people will strictly fast all day, from a meal just before sun-up to meal just after sun-down (iftar), around the world each year.  Doctors have studied the effects of Ramadan.  The surprising thing is that there is very little weight loss, around 1 -1.5kg on average, and most patients gain that weight back in the month following Ramadan.   The factor noted in these studies has been that the food eaten at iftar, in some families and cultures, can be relatively rich, calorie-dense, or high in carbohydrates.  There is a huge global and culture variability on how the breaking of the fast in the evening is practiced.   While more needs to be done to understand this, it does support the idea that just time-restricting eating without also making healthy food choices is unlikely to make a difference to health or weight.

Fasting for spiritual or religious reasons:

Religion or spirituality, regardless of your personal or cultural practice or preference, has well documented health benefits. And fasting has been part of religious observance for thousands of years. So, if you ask your doctor about guidance to engage in your faith or spiritual practice, we are going to help.  Most faiths exempt those with chronic health conditions, in particular most faith guidelines specifically mention diabetes, mothers who are pregnant or breast-feeding, and children in their standard exemptions.Patient who have a chronic health condition or are on medications that are advised to be taken with food should always talk to their doctor about fasting.  If you are struggling with fasting (feeling weak or faint), consider talking to a Registered Dietitian** to help with health meals that give you more energy to get through the day.

1. Drink water at iftar (breaking evening fast) and throughout the night. Remember to drink plenty before sunrise even if you aren’t feeling thirsty.

2.  Plan healthy dinners to break your fast that include whole grains, vegetables, fruits, lean source of  protein, and healthy source of fats, like nuts.

3.  Control portion size, and don’t overeat.  Eating slowly can help.  Some people are so hungry that they eat faster than their stomach can tell them they are full, which at the very least, can lead to indigestion.

4. Stay Active:  Consider changing your work-out to evening time after your meal.  Avoid strenuous exercise when you cannot drink water to rehydrate.

5.  Plan a healthy suhoor/sehri (pre-sunrise meal).  To give you the most energy for the day ahead, try to include: Whole grains such as whole grain bread and oatmeal, fruits and vegetables, a protein souce such as milk, yogurt, eggs, or  nuts, and include healthy fat sources such as nuts.

What faiths fast? (most of them!)

Roman Catholics fast 2 days a year, though in some cultures, Roman Catholics fast on Fridays or have highly restricted diets during lent.  Orthodox Christians have 4 fasts per year, 40 days each before Christmas and Easter, and two additional fasts of around 2 weeks each.  Judaism observes 6 days of fasting per year, 2 of which are 25-hour fasts.  Fasting, known as vrats, is important to those of the Hindu faith, but practice can vary greatly. Buddhism, likewise, has fasting but the practice can vary by culture.

What can religion tell us about healthy fasting? 

In religious fasting, it is not just abstaining from food.  Most faiths usually include abstaining from alcohol, sex, and tobacco.  The breaking of the fast is traditionally a meal shared with family and friends.

I had a colleague for years who could best be described as a curmudgeon:  always that little bit cranky.  When Ramadan rolled around the first year, I was worried – I wasn’t keen to meet him when he hadn’t had his coffee.  However, he was absolutely kind, helpful, and charming all through Ramadan.  Constantly smiling.  In short, unrecognisable. About 2 weeks in, I actually asked him why he was in such a good mood.  He replied that he felt that he was obligated to also give up his complaining and griping as part of fasting, and he could do that once a year.

The take-away is that if you are fasting, those other things – not just the not eating – also matter.   For example: look after your stress, stop smoking/vaping, don’t take alcohol or reduce to low-risk limits, connecting with family and friends.

So, what’s the bottom line:  Should I fast?

Absolutely recommended, if you are physically healthy and you want to do this to practice your faith.  If we are talking health, no harm in trying it if you are physically healthy and want to see if it has health benefits for you for a period – but it is definitely not right for everyone.

* If you are on a medication or have a health condition and are unsure whether it is safe for you to fast, talk to your doctor.

** The recognised qualification to give nutrition advice in Ireland is INDI and CORU registration. Always choose a registered dietitian.