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Intermittent Fasting and Pregnancy: Why it’s a Mismatch

I never intended to write about intermittent fasting and pregnancy. And yet, here I am.

In the past few months, I’ve been asked about intermittent fasting and pregnancy more times than I can count and it’s time to address this topic head on.

First off, let’s make sure we get our terms straight.

What is Intermittent Fasting?

Intermittent fasting (IF) is the choice to voluntarily abstain from eating for periods of time (fasting) while choosing to eat during other periods of time. The length of the “fasting window” or “eating window” varies, with some choosing to fast for 16+ hours per day, while others may go 24 hours or longer.

The most popular version at the moment (it’s 2019 at the time of writing, just FYI) is a 16:8 fast, meaning you eat all of your food for the day within an 8 hour window and abstain from food for the remaining 16 hours in the day (water and sometimes other non-caloric fluids are “permitted” during the remaining 16 hours per day).

This is often accomplished by skipping either breakfast or dinner. Intermittent fasting may be, but is not always, combined with caloric restriction. That means you might consume the same amount of food, just within a shorter period. Or, you may intentionally or unintentionally eat less than usual.

It is also often, but not necessarily, combined with specific diets. Many low carbers, for example, combine this way of eating with some variation of intermittent fasting (intentionally or unintentionally), since a lower carb diet is often more satiating, keeping hunger at bay.

Why do People Choose Intermittent Fasting?

There’s a fair amount of data (mostly from adult men) showing that fasting can improve body composition, blood sugar metabolism/insulin sensitivity, promote weight loss, improve cognitive function, clear out dead/damaged cells (aka stimulate “autophagy”), and reduce inflammation. This article has a comprehensive overview of the topic.

The above benefits are all well and good, however we always need to consider CONTEXT when thinking about whether or not a specific health practice is beneficial to us or not given our unique set of circumstances. One of those special circumstances is pregnancy.

Note that nearly all fasting experts I’ve talked with do not condone fasting during pregnancy.

When I spoke at Low Carb Denver on the science and controversy surrounding low carbohydrate diets and pregnancy, I was asked repeatedly by attendees about my opinion of intermittent fasting and pregnancy.

I usually responded with the following:

“Before I share my thoughts, I’d love to hear what makes you ask this question.”


“That’s an interesting question. Do you have any personal or professional experience so I can understand how this topic got on your radar?”

Their answer was often some version of a personal beneficial experience with fasting (outside of the context of pregnancy) or a professional interest in the research (or lack thereof) on fasting with regards to pregnancy (they’re usually well aware of the non-pregnancy research on fasting).

Then I’d usually follow up with some questions about their personal/professional experience specifically with pregnancy.

Intermittent Fasting and Pregnancy: Why it’s a Mismatch

If you’ve ever been pregnant, worked with pregnant clients, or spent a lot of time with a loved one/partner who’s pregnant, you’ll realize that fasting is usually a mismatch for pregnancy. If you’ve not had any experiences of the above, then you (probably) won’t know this.

Let me explain, trimester by trimester, from a mindful eating and physiological perspective. Then I’ll go into some research.

First Trimester & Intermittent Fasting: It is even possible?

Say you find out you’re pregnant. The earliest this can happen is ~2 weeks after ovulation or ~4 weeks after your last menstrual period, so you’re already 4 weeks along by the time you know.

By weeks 6-8, nausea and food aversions usually begin thanks to massive—and necessary—hormonal shifts happening to help you sustain the pregnancy, provide fuel for the rapidly dividing cells (all of baby’s internal organs have developed their basic structure by 8 weeks), and support your thyroid as it adapts to provide a huge boost to your metabolism (and support baby’s early brain development).

Your blood sugar also tends to dip in the first trimester as insulin sensitivity temporarily improves and your pancreas starts to grow and produce more insulin (the big surge in insulin production happens later in pregnancy, but this is accompanied by insulin resistance—not so in the first trimester!).

Even for those with type 1 diabetes, who DO NOT otherwise produce insulin, their insulin dosages often drop temporarily in the first trimester (it’s theorized that maybe the beta cell expansion of pregnancy might allow them to produce *some* insulin and/or the temporary drop in insulin resistance reduces the need for exogenous insulin).

What does all this mean?

In the first trimester, you’re probably hungry, but too nauseous to eat much at one sitting (annoying, I know! #solidarity). To settle your stomach, you probably want to eat more carbs, which don’t keep you full for very long, meaning you’re hungry again relatively quickly.

Some people would just tell you to “power through” and eat more fat/protein, which are more satiating, but nausea/food aversions usually mean large portions of those foods don’t sit well or are entirely unappealing.

Your stomach might be so unsettled, unsatisfied—confused, maybe?— that if you wake up in the middle of the night with an empty stomach, your nausea will get even worse. The only way to settle it and get back to sleep? Probably to eat something! (FYI – listening to your body is a wise choice. I kept snacks at my bedside so I didn’t have to trek to the kitchen.)

What’s the solution to all of this?

EAT—and eat as frequently as you need to while you’re in survival mode. You might be eating tiny bites whenever you’re able. It might be 8x per day. It might be 18x per day. Don’t freak out!

Eat whatever keeps you going (more detail on nutritional strategies to manage nausea are explained in Ch 7 of Real Food for Pregnancy).

As someone who relatively recently went through the first trimester again (second pregnancy), let me tell you… intermittent fasting was entirely unimaginable in that phase. HARD NO. That would have gone against every single message my body was sending me. I often had to eat right before bed, sometimes have a snack in the middle of the night, and most days eat something before even getting out of bed.

I’ve worked with HUNDREDS of pregnant clients one-on-one and hear from literally THOUSANDS of mamas via email/messages. My experience of the first trimester isn’t an anomaly. This is normal.

There is absolutely no way I would have been able to eat enough food to sustain myself by compressing my “eating window” into 8 hours. 100% impossible. So why would I try to force it?

Second Trimester & Intermittent Fasting: Maybe, but maybe not.

Some women have a bit of a respite in the second trimester, where nausea and aversions fade (for me, they gradually dissipate by week 15-16, but it’s highly highly highly individual).

This means that for some, a return to a more balanced diet that’s less heavy on the carbs happens naturally. You may notice that you can get through a larger meal, eat enough fat/protein/fiber to stay satisfied for longer, and generally feel a little less urge to eat quite as frequently.

That said, I still don’t think it makes sense to arbitrarily limit your eating window to 8 hours. Your primary nutritional goal in pregnancy should be to meet your micronutrient needs first and foremost. The less time you “allow” yourself to eat, the fewer opportunities you get to eat those micronutrients.

If, by chance, you’re a person who naturally and truly feels GOOD eating two larger meals and you’re able to meet your calorie, protein, and micronutrient requirements with something that resembles intermittent fasting without having to force it (meaning, you’re not hungry during this “fasting window”), then by all means, keep on keepin’ on.

For what it’s worth, I have yet to meet that person. However, it is theoretically possible, so I don’t want to dismiss this entirely. The key is that it isn’t forced, but rather a pattern that your body naturally falls into when you’re following mindful eating cues.

Third Trimester & Intermittent Fasting: Are you kidding me?

By the third trimester, your belly is typically so large that it compresses your stomach, making large meals a no-go.

This stage of pregnancy is when caloric, protein, and micronutrient needs are at their highest.

Can you feasibly eat all 2200-2600 calories that you need within an 8 hour window without experiencing heartburn or extreme abdominal distension? Let me tell you, your abdomen feels distended enough with baby taking up so much room!

What about protein? Data from a 2015 study—the first ever to directly estimate protein requirements in pregnant women—found that protein needs are actually 73% higher than the current estimated average requirement—in late pregnancy. That means a person who weighs about 150# pre-pregnancy requires over 100g of protein per day in the third trimester. That’s a lot of protein to fit into the, say, 2 meals and 1 snack you can reasonably fit in an 8 hour window while still meeting your other nutrient needs and not feel like your belly is going to burst.

What about your blood sugar? Insulin resistance is at its peak in this stage. High blood sugar readings taken one hour after a meal are predictive of excessive fetal growth. It’s one of the reasons that dietary strategies for gestational diabetes involve splitting up meals and snacks throughout the day. Sure, if you’re eating lower carb, you can minimize these spikes, but even as a person with excellent blood sugar metabolism, large meals spike my blood sugar much more than smaller ones.

Some would argue that given the data on intermittent fasting in men shows improvement in blood sugar metabolism that the same should hold true in pregnancy, but as someone who’s worked extensively with gestational diabetes, I can tell you it’s just not necessary.

The vast majority of my clients have excellent blood sugar readings with diet alone while eating 5-6x per day (the lower carb, nutrient dense diet outlined in Real Food for Gestational Diabetes) and not intentionally “fasting” beyond sleeping at night—and even that is usually 10-12 hours or less between dinner/bedtime snack and breakfast.

Are There Studies on Intermittent Fasting & Pregnancy?

Not many. Most of the studies are in relation to religious fasting, like the practice of Ramadan in the Muslim faith.

In case you’re not familiar, “Ramadan is a period during which food and fluid ingestion is not allowed for Muslims between pre-sunrise and post-sunset hours for one month every year.” The fast is broken each evening with one large meal after sunset.

So far, the data on the effects of Ramadan on pregnancy outcomes and infant/child health is mixed. Some data looking solely at pregnancy do not find significant impacts on fetal development (such as fetal movement, oxidative stress, uterine arterial blood flow, and birthweight), while others looking at long term health of the offspring have found some concerning findings (such as lack of stature in adolescence and lower scores on cognitive tests if mothers participated in fasting during Ramadan). Worryingly, some research has shown an increased risk of mortality among children under age 5 years if their mothers participated in Ramadan fasting during the first trimester.

One study showed “significant alteration in the frequency and pattern of human fetal breathing movements” during Ramadan fasting at 30 weeks of pregnancy. It’s unknown what significance this has, but raises concern.

Another, which looked at the effects of Ramadan fasting in 168 women compared to 156 women who did not participate in fasting found that participation in fasting resulted in a significantly higher rate of gestational diabetes, labor induction, C section delivery, and frequency of admission to the neonatal intensive care unit. This is in contrast to a more recent study, which found lower rates of gestational diabetes among women who participated in Ramadan fasting in pregnancy. Abdominal visceral fat mass also appears to decrease among women who participate in Ramadan fasting.

A large review of studies on Ramadan fasting and pregnancy published in 2018 looked at 22 studies encompassing 31,374 pregnancies (including 18,920 pregnancies exposed to Ramadan fasting). Birth weight and risk of preterm delivery were not significantly affected by maternal fasting, however, placental weight was significantly lower in fasting mothers. The significance of this finding is unknown, however some studies suggest low placental weight is associated with malnutrition, poor transfer of nutrients to the fetus, and higher rates of adverse fetal outcomes.

The researchers conclude:

“Ramadan fasting does not adversely affect birth weight although there is insufficient evidence regarding potential effects on other perinatal outcomes. Further studies are needed to accurately determine whether Ramadan fasting is associated with adverse maternal or neonatal outcome.” (BMC Pregnancy and Childbirth, 2018)

What does this research mean?

We really don’t know that much about the effects of intermittent fasting during pregnancy. The data is mixed. Ultimately, this is yet another one of those cases where you need to use personal and clinical judgement.

If your choice to fast is a religious one, that’s up to you.

If your choice to intermittent fast in pregnancy is based on health reasons, I don’t think we have enough evidence to say that it’s guaranteed to be healthier (or even a risk-free choice). Based on my clinical experience and the high prevalence of micronutrient deficiencies among pregnant women (it’s estimated that 47% are deficient in at least one micronutrient in the United States), my opinion is that intermittent fasting is a mismatch for pregnancy.

Although this represents an extreme example, the Dutch famine of 1944-1945, during which food rations were below 1,000 kcal/day for a period of 5 months, showed us that children exposed to this in utero experienced a higher rate of chronic disease later in life. While this arguably does not represent intermittent fasting, but rather starvation, it does give you pause at what the long term consequences could be of under nutrition in pregnancy.

Is it really wise to intentionally minimize our food/nutrient intake at a time when so much is at stake?

Beyond the overnight fast that you naturally take every night while you sleep (typically 12 hours or less between meals), “forcing” your body to go without food during pregnancy is probably not the best call.

Why Intermittent Fasting is a Mismatch for Pregnancy

All in all, most of the typical arguments for intermittent fasting don’t make sense in the context of pregnancy. This is naturally a time when your body very intentionally accrues body fat, gains weight, and preferentially directs nutrients to the embryo/fetus to support rapid growth.

On one of the podcast interviews I appeared on, the host likened an optimal diet in pregnancy to a body building diet. In some ways, this makes a lot of sense. You’re literally growing a human from scratch—that’s certainly counts as body building.

To summarize, here are the reasons you probably don’t want to intermittent fast in pregnancy:

  • Micronutrient and calorie needs are high – Intentionally limiting your food intake to a small window can make it difficult to meet these needs.
  • Protein needs are high – This is the most filling and satiating macronutrient. It’s going to be very hard to meet those needs in a short eating window, especially in early or late pregnancy.
  • Early satiety – In late pregnancy, lack of space in your stomach can make it hard to eat large portions at a time without experiencing heartburn or digestive discomfort.
  • Nausea/food aversions – Do I even need to explain? Both of these make small/frequent meals (grazing) more appealing than big meals. If you’ve never been pregnant, imagine how you feel when you get food poisoning or severe motion sickness. It’s that—queasiness often coming in waves, often lasting for hours, days, or months at a time. Large, infrequent meals typically worsen these symptoms.
  • Metabolism – Your body wants you to gain weight and grow a baby. This is not the time to be thinking about “autophagy” or avoiding gaining weight/fat mass. These hormonally induced changes in body composition happen for a reason. Don’t fight it. Data from adult men do not necessarily apply to pregnancy. (If you believe your prepregnancy weight puts you in a category where you’d be better off limiting weight gain, please review the section on weight gain in Ch 7 of Real Food for Pregnancy. There is a ton of nuance to this topic and weight goals require a personalized approach.)
  • Lack of research – The data on intermittent fasting in pregnancy is mixed. We can’t draw strong conclusions at this time, but there’s enough concerning data available to make you pause.

All told, when someone asks me about intermittent fasting and pregnancy, what I really want to ask is: WHY?

I have yet to hear an argument in favor of intermittent fasting and pregnancy that has robust data to back up the logic. That said, I’ll eagerly read any research studies you come across on the topic!

I fully recognize we don’t have all the answers at this time and I’m always willing to adjust my recommendations as new data becomes available.

Until then, if you’re pregnant, keep eating nutrient-dense real food at whatever interval is working for you. When so much is unknown about intermittent fasting and pregnancy, default to prioritizing micronutrients and honoring your body’s mindful eating cues.

Until next week,

P.S. – On a related note, if you have questions about weight gain in pregnancy, particularly if you’re a practitioner who counsels clients on this sensitive topic, I recommend you check out the recent Deep Dive Discussion webinar on Challenging Counseling Questions that I recently co-hosted via the Women’s Health Nutrition Academy.

The main questions we tackled were:

  • How do I best counsel a vegan/vegetarian client on prenatal nutrition?
  • What do I do with clients struggling with body image and weight before and during pregnancy?
  • How do I set realistic expectations for the timeline and results with my infertility clients?

This webinar is available for no cost. Yep, 100% FREE. Check it out here. Registered dietitians earn 1 CEU for attending.


  1. Kunto, Yohanes Sondang, and Jornt J. Mandemakers. “The effects of prenatal exposure to Ramadan on stature during childhood and adolescence: Evidence from the Indonesian Family Life Survey.” Economics & Human Biology 33 (2019): 29-39.
  2. Dikensoy, Ebru, et al. “Effect of fasting during Ramadan on fetal development and maternal health.” Journal of Obstetrics and Gynaecology Research 34.4 (2008): 494-498.
  3. Karimi, Seyed M., and Anirban Basu. “The effect of prenatal exposure to Ramadan on children’s height.” Economics & Human Biology 30 (2018): 69-83.
  4. Majid, Muhammad Farhan. “The persistent effects of in utero nutrition shocks over the life cycle: Evidence from Ramadan fasting.” Journal of Development Economics 117 (2015): 48-57.
  5. Ozturk, Ebru, et al. “Effect of Ramadan fasting on maternal oxidative stress during the second trimester: a preliminary study.” Journal of Obstetrics and Gynaecology Research 37.7 (2011): 729-733.
  6. Mirghani, Hisham M., Muntha Salem, and Sarath D. Weerasinghe. “Effect of maternal fasting on uterine arterial blood flow.” Journal of Obstetrics and Gynaecology Research 33.2 (2007): 151-154.
  7. Stein, Aryeh D. “Ramadan, Pregnancy, Nutrition, and Epidemiology.” American Journal of Epidemiology (2018). Vol. 187, No. 10.
  8. Mirghani, H. M., et al. “The effect of intermittent maternal fasting on human fetal breathing movements.” Journal of Obstetrics and gynaecology 24.6 (2004): 635-637.
  9. Mirghani, Hisham M., and Omer A. Hamud. “The effect of maternal diet restriction on pregnancy outcome.” American journal of perinatology 23.01 (2006): 021-024.
  10. Safari, Kolsoom, Tiran Jamil Piro, and Hamdia Mirkhan Ahmad. “Perspectives and pregnancy outcomes of maternal Ramadan fasting in the second trimester of pregnancy.” BMC pregnancy and childbirth 19.1 (2019): 128.
  11. Gur, E. B., et al. “Effect of Ramadan fasting on metabolic markers, dietary intake and abdominal fat distribution in pregnancy.” Hippokratia 19.4 (2015): 298.
  12. Glazier, Jocelyn D., et al. “The effect of Ramadan fasting during pregnancy on perinatal outcomes: a systematic review and meta-analysis.” BMC pregnancy and childbirth 18.1 (2018): 421.

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Lily Nichols is a Registered Dietitian/Nutritionist, Certified Diabetes Educator, researcher, and author with a passion for evidence-based prenatal nutrition and exercise. Her work is known for being research-focused, thorough, and unapologetically critical of outdated dietary guidelines. She is the author of two bestselling books, Real Food for Pregnancy and Real Food for Gestational Diabetes.


Leave a comment
  1. Hi Lily –
    So I AM doing intermittent fasting – I’ve cleared it with my dr – it’s working great for me. I started doing it at 29 weeks, I’m currently almost 33 weeks. I eat my last meal (a small low carb snack) around 8pm and I don’t eat until usually 12pm the next day. I was diagnosed with gestational diabetes – which is why I am doing this. In the morning when I wake up my blood sugar is usually around 102 – when I’m about to eat (about to end my fast) my blood sugar has dropped to a normal fasting rate (under 95). I eat low carb & high-ish fat the rest of the day and typically all my post meal readings are way under 130. I clean fast – meaning I don’t put anything in my 1 cup of coffee & stick to plain water, unflavored sparkling water, etc. this is because ANY flavor in your beverage raises insulin. I feel SO much better. I had gained about 50 pounds (I’m only 5’1”) and now I haven’t gained since May 16th yet baby is healthy and growing! Dr Fung gives a lot of great info about fasting and insulin reduction in YouTube talks and his books The Obesity Code and The Diabetes Code – while he doesn’t recommend fasting for an entire day while pregnant- I have read that he says it’s ok to skip breakfast – which is basically what I’m doing. His theory (based on a ton of clinical data) is that your body has time to recover when you are not constantly feeding it. Insulin levels go down if you can go 12-18 hours not eating. I am not hungry when fasting – I actually feel a lot more alert, clear headed and energetic when fasting. I do not subscribe to the “calories in calories out” theory – which I feel is outdated and has proven to be false (not all calories are created the same; 100 calories of jelly beans is not the same as 100 calories of broccoli). I eat until satisfied and am making sure to eat healthily. If you think about it – it’s only been In the past 100 years or so that we’ve even been able to MONITOR how many calories we are eating! Plus – we have not had so much food available to eat 6 times a day! Since the beginning of time basically pregnant had to work for their food (farming, hunting) and then ate till satisfaction. Since being diagnosed I cut out all processed sugar, stevia and eat a controlled amount of fruit and usually pair it with a fat/protein. Another book that is GREAT is Delay Don’t Deny – now of course – I’ve heard a million times not to fast while pregnant- but after seeing my personal results and getting it cleared with my doctor (whom I respect very much) I’m very glad I made this decision. Another great documentary to watch is “Fasting”.

    • Thanks for sharing your experience!

  2. What about intermittent fasting while breastfeeding? I’m guessing this would also be counterintuitive, but I’d like to lose the leftover belly from pregnancy…

    • See my response to Leah!

  3. What are your thoughts on intermittent fasting while breastfeeding?

    • Also a mismatch, at least in the period of exclusive breastfeeding and while baby is heavily reliant upon mama for nutrition (which for moms who choose to breastfeed long-term and depending on how quickly the baby takes to solids, could be a year, 18 months, or more). Nutrient needs, including numerous micronutrients, are HIGHER during breastfeeding and postpartum recovery than they are during pregnancy. I explain this in greater detail in these two webinars:
      Postpartum Recovery & Nutrient Repletion
      Nutrition for Breastfeeding: Effects of Maternal Intake on the Nutrient Content of Breast Milk

      • hi! Don’t you think though that if breastfeeding while IF and mum’s body would be running low on energy / nutrition. then the mum would feel more hunger and some cravings? I deeply believe that the body knows better what it needs if we just listen to its signals, instead of wanting to control and monitor how it should be fed. I have been IF (16/8) and on a low-carb way of eating for the last 3 years and that was such a relief from all those days where I forced myself to eat breakfast in the morning because I was told it was better for me, only to feel sluggish and tired all day, while at the eh same time obsessing over food and needing to eat something – often poor choices as the healthy ones weren’t satisfactory – every couple hours. With IF I feel alert and light and so well in my skin, yet I acknowledge that some days I get hungry before the usual window start and then I just eat! IF is not a rigid way of eating, or it shouldn’t be. Often articles on “should you IF” have the assumption that people do it in order to loose weight, or some similar goal. Very rarely is it discussed that for many people it is a back-to-basics, natural way of eating that changes our quality of life for the better – like our ancestors. Thanks for your detailed article by the way!

  4. Thank you for posting this article! It’s really helpful to know for someone who intermittent fasted for health and balancing blood sugar prior to pregnancy. Though I stopped IF once I found out I was pregnant, it’s good to know that my decision was the right one! IF has many health benefits, so at first I wasn’t sure if I should try to keep it up or not. Thankfully, I was reading your book Real Food for Pregnancy and decided it was much better to eat intuitively, and since I was hungry all the time, IF was out!

  5. Hi Lily,

    Happy you wrote about IF during pregnancy 🙂
    Looking forward to read the references you posted.

    I’ve been doing IF since i was a kid and tried to not skip meals when i found out I was pregnant. I did this mostly because my doctor told me that IF will be harmful for the baby and myself.
    For me , that is when nausea started to appear, no matter what foods I ate or removed. As soon as i returned to my usual routine of IF, morning sickness and nausea disappeared and never returned.
    I did not limit calories or forcibly increase them, did not have gestational diabetes or any other complications. I did gain weight which after birth slowly came off.

    I have a healthy 2 year old child who eats everything from liver to cupcakes 🙂

    It’s amazing that we have tests, studies and clinical trials but everyone is unique. Even if 100000 people react the same way there are always 2 or 3 who will differ and should not be ignored or treated the same as others.
    Every mother counts and i feel generalization is more damaging than helpful.
    What the medical world is failing to do, for me at least, is actually to listen to what i need and where my pain is.
    There is no more time for affordable individual care, generalization gets the job done faster and cheaper.

    Thank you,

    • Thanks for sharing, Maria!

  6. Let me just say, I’m a faster. When I was doing my weight-loss (went from 189 to 129) and while I did eat mostly a ketogenic diet, I would fall into natural fasting patterns. Once my weight got into the 140s, I started doing longer fasts, sometimes for 48-72 hours and I would drink bone broth/water. I love fasting. However, now that I’m 13 weeks pregnant. I can confirm there’s no way in heck I could’ve (or would’ve) done any fasting. All my favorite “keto” foods are very difficult to eat and foods I did NOT want to eat during pregnancy are sometimes the only thing I can stomach. Meat and fruit taste bad to me, so it’s quite a spectrum. I understand people don’t want to gain a lot of weight, but the best thing you can do is listen to your body and focus on getting yourself & baby best nutrition, if you can stomach it. (PS – Love your book, I check it over almost every day.)

    • Yeah, I regularly hear from people with your experience: previously felt good with some intermittent fasting, not so while pregnant. As you can see in the comments, there are exceptions. Following those mindful eating cues and meeting essential nutrient requirements is the #1 priority, wherever that leads you.

  7. Once again, Lily, you NAILED IT!
    I can’t tell you how much I appreciate your willingness to hit on controversial issues with a sound, scientific approach (versus rhetoric).
    I am an intuitive eater that has always naturally done IF. But as you so eloquently described in the article, it was impossible to fast while I was pregnant, without feeling constantly nauseous. So I ate small snacks throughout the day, with my largest meal in the evening (Something about going to bed with a full belly feels so nice and sleepy for me!).
    So my personal experience with IF definitely resembles what you described above.

    And the next question for you – what about breastfeeding and IF? After I had my baby, I continued following my body’s cues, and naturally fell back into an intermittent fasting routine. A typical day comprises of coffee with full-fat cream in the morning (I know, some will say that because of this, I’m not actually doing “IF” but I would disagree, based on how I feel). I don’t eat my first meal until 3 or 4 pm, and I’m naturally done eating at 9 or 10 pm.
    My milk supply is heaviest in the mornings to afternoon (I’m like a milk geyser, lol!), and naturally tapers off in the evenings (which is pretty typical). And my little guy is the CHUNKIEST baby I’ve ever had! I do wonder if my nutrition lifestyle means that my milk has a higher fat content…
    Anyways, I know many women are worried about doing IF while breastfeeding, and above all else, I would say eat intuitively! But my intuitive IF approach is a lovely way to eat for me.

    • Glad it resonated. With regards to intermittent fasting and breastfeeding, see my response to Leah. <3 If you're feeling good, meeting your nutrient requirements for postpartum repletion, getting enough calories, and have ample supply, carry on. That said, most people I hear from who try to adopt IF while breastfeeding struggle with one or more of the above, so stay mindful of those and consult your healthcare provider for personalized guidance.

  8. Thanks for another great post, Lily. Do you have any views on IF pre-conception?

    • I have the same question so I thought I’d comment a reply to yours. I am trying to conceive while also trying to manage my remaining weight from my last pregnancy. Will IF impact fertility? I have heard it has been used among women with PCOS but I do not know the specifics.

      Thank you for all your insight thus far!

      • Intermittent fasting *can* be helpful prior to conception, but it really depends on the person and underlying health status.

        For someone who’s insulin resistant or has a significant amount of weight to lose, intermittent fasting (combined with a calorie and micronutrient-sufficient diet during the eating window) might work well. For someone struggling with adrenal fatigue, or underweight, or has a history of restrictive/disordered eating, it might not be the best idea. There are so many variables, that I suggest working with an informed health provider on the specifics.

  9. I can’t imagine IF during pregnancy. I’ve been practicing IF with a 16-18 hour fast since my baby was 10 months old(he’s now 2). This is my 4th nursling and I’ve never felt better (or looked better) postpartum.

    • Thanks for sharing your experience, Bethany!

  10. Similar to Maria (who commented above), I am a totally natural intermittent faster. I was never a breakfast person but always ate because my mother said I had to. Once I became an MD and started learning about IF I started to do 16:8 every day (along with a two meal per day low carb diet) and felt substantially better than when I would previously eat breakfast. My brain was much sharper in the mornings and I no longer faded quickly before lunchtime. I was also able to eat a healthier lunch since I was no longer starving.

    After finding out I was pregnant I looked for information on IF in pregnancy and was disappointed that even you didn’t support the concept. My doctor told me I should avoid any sort of dietary restriction so I started forcing myself to eat breakfast. The result was nausea that lasted all day and would only abate if I ate small amounts of carbs and other junkie foods that only made me feel worse after. I would do this for a couple of days then take a day off and instantly I felt normal and well again. After trying this experiment 3 or 4 times with identical results each time I went back to my usual 16:8 fasting regimen with 2 meals per day, although my dinners are a bit more liberal low carb than they used to be and I do indulge a bit more on weekends. I feel fantastic when I stick to it and bad when I deviate. FYI my pre-pregnancy BMI was 21 so it’s not like I’m surviving off of significant fat stores when I fast, and my weight gain was adequate during my pregnancy.

    Is it possible to fast in pregnancy and still feel good? Absolutely! I am definitely one of those people who naturally feels good while following this way of eating and I feel way worse when I deviate. Part of me also wonders whether it’s the frequent eating of carby foods that causes some people to feel nauseous in pregnancy (but hey, what do I know, I’m just an MD with an interest in metabolism and nutrition).

    I posted this comment with the hope that you will take into account stories like mine and Maria’s when you counsel your clients about fasting in pregnancy (although I recognize that there are no authorities who recommend fasting in pregnancy, mostly because of the lack of any good research on the topic). I used my clinical and personal judgement to decide what was best for me, and I would not hesitate to tell my patients to do the same.

  11. I don’t practice intermittent fasting, but my typical eating patterns are similar. Just before getting pregnant, I was doing phenomenally on a 0 carb diet, which allowed me to regain my natural hunger and satiety cues, as well as clear up long-term digestive issues. Food aversion and eating carbohydrates during my first trimester led me to not only lose those natural cues, but led to digestive distress, as well as a rapid 20 lb weight gain. I also felt pressure and guilt to conform to conventional pregnancy diet dogma. At last, I have just entered the third trimester and I’m eating primarily nose to tail zero carb, with the exception of the odd experiment with a fruit or vegetable. However, every time I added a fruit or vegetable my digestion acts up, taking a few days to normalize again. I eat when I’m hungry, which could be 3 to 6 hours after waking. I think this is very different from actually trying to postpone meals, but I still have a bit of a guilt complex even if this is natural for my body. Reading your article helped to put my mind at ease. But one question. If I’m getting all my nutrient needs in one meal or two a day and that is what makes me feel my best, should I feel confident in trusting my body this way?

  12. Hello! I am currently 9 weeks pregnant and breastfeeding a 1 year old. I am so so nauseous all the time. Though my family and I try to adhere to a clean whole foods diet, the only food I don’t find absolutely repulsive and I can possibly imagine eating most of the time is childhood junk food; canned pastas, pizza pockets, frozen entrees, McDonald’s etc. When I give in and eat it, I feel worse. I know I am sensitive to wheat and dairy which these often contain but I literally cannot stand the sight or smell or taste of anything healthy! I find myself going long periods of time without eating anything at all. The food aversions are so strong!
    I am all too aware of the drawbacks of eating these “food like products” I don’t know why I revert back to that after years of healthy, conscientious eating!?
    In a case like mine, is it better to give in to McDonald’s than eat nothing??

  13. I figured that research regarding Ramadan would come up during this discussion, and I am happy to see this commentary. I think it is important to note that pregnant women are exempt from fasting during the month of Ramadan per religious texts. They’re also exempt during breastfeeding. So, while some women do participate – they do not have to and in many cases are religiously discouraged. This comment is not relative to the research per say, but interesting in regards to women practicing some form of fasting.

    • Yes, that’s correct Hana. The pregnant Muslim clients I have had reiterate your points; some choose to fast, others abstain.

  14. Great post and super informative. What about intermittent fasting while TTC? I am going to guess based on your book – no, but would love to hear a direct response.

    • Please see my response to Eliza’s question.

  15. I don’t think it specifically mentions it during pregnancy but the uptick in curiosity may be from the recently popular Netflix special UnWell. As I was watching it, it reminded me “hey I got an email about this this morning!” Maybe this is why she’s suddenly getting inquiries about it.

  16. Hello, I have your book and I really enjoyed it. I used to do intermitted fasting and low carb before getting pregnant. I am now breastfeeding my 4 month old and wondered if I can start intermitted fasting again? I am scared of messing with my milk supply but also wanted to get rid of the last stubborn kilos. Do I wait after I stopped breastfeeding to start intermitted fasting again?

  17. Hi, thank you for this. I think women definitely need to listen to their bodies while pregnant and not force fasting. I am currently fasting. I feel good, it feels like a natural eating pattern for me, and I’ve been finally losing the extra weight I gained in my last pregnancy. However, I am trying to conceive. I would really like to continue trying to lose weight and maintain health while trying to conceive (I’m about 20 lbs overweight), but is IF a risky way to do while trying to get pregnant? The moment I get that second pink line I plan to stop fasting and listen to my new hunger cues, but I don’t want to give up IF before that.

    • Generally speaking, intermittent fasting is OK preconception as long as you’re not undereating or falling short on micronutrient needs; it can be beneficial for cases of infertility related to insulin resistance/PCOS if done carefully. Best of luck to you!

  18. Hello! Thank you for the article! I am searching for answers to help my morning sickness. Snacking does NOT work for me. I am 6 weeks pregnant (from my last period). However, I can’t seem to stomach food or even want it until the late afternoon or evening. Even then I don’t eat very much. I am not too worried about it considering I read elsewhere that you don’t need extra calories until later in pregnancy and I am on the smaller side 5’2 110-115lbs, and I do basically nothing all day (I am on college break) so it might be enough food for me. I wish snacking would solve my nausea, however, I will vomit with even the smallest nibble of food if I have bad morning sickness. I tried snacking before bed when I didn’t feel sick, however, I just threw up in the morning. I have tried working out to help with my morning sickness, but I am just so tired. I am wiped out after simple household tasks. I just want to sleep all the time. I know I am dehydrated because I just sip water all day because if I drink a lot at once I will throw up. Do you have any advice for me?

  19. This is a great article, as well as an informative comments section. Thank you!! : )

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