Intermittent Fasting While Pregnant – Is it Safe?

You will go through several different sizes of clothes during pregnancy as your baby bump grows. In fact, it is normal and quite healthy for women to put on weight during pregnancy. But when weight gain during pregnancy exceeds the healthy amount, it could jeopardise the health of the mother as well as the fetus. In such cases, pregnant women looking to lose weight during pregnancy think of trying intermittent fasting in pregnancy. On the other hand, some may look into intermittent fasting due to religious reasons. If this is the case, remember that most religions exempt pregnant and breastfeeding mothers from partaking in any fast. But, is it safe to intermittent fast while pregnant? Whatever’s fuelling your interest in intermittent fasting while pregnant, there are some things you should look into.

What Is Intermittent Fasting?

Intermittent fasting involves fasting and then eating at controlled timings, which are done over a period of time. There are three types of intermittent fasting. This involves fasting every alternate day, fasting for a few hours in a day and eating only at certain times, and periodic fasting, where you remain fast for a few days at a time.

Most people tend to opt for the first kind, especially if they are indulging in intermittent fasting to lose weight. Here, they eat their calories only within a specific window they have set for themselves. Some will choose to fast for 16 hours a day and eat only during an eight-hour window. This is referred to as the 16:8 method. Others may opt for the 5:2 method. This is where they eat normally for five days and then fast or eat low-calorie food for the other two days.

Some believe intermittent fasting may reduce inflammation and lower blood pressure, cholesterol, and blood sugar (1). In fact, some research also suggests that fasting may help reduce the risk of cardiovascular diseases, diabetes, and some cancers (2).

Weight loss is a significant area of study related to intermittent fasting (IF), as fasting is thought to aid in losing weight by prompting the body to rely on fat reserves. Additionally, it may assist in lowering total calorie consumption (1).

A 2007 study has shown that those who practised intermittent fasting managed to lose around 8% of their body fat in just two months (3).

Can You Do Intermittent Fasting During Pregnancy?

Let’s come to the burning question: ‘Is intermittent fasting safe for pregnant women?’ ‘Are there any benefits of intermittent fasting when pregnant?’

It is not recommended that women who are pregnant go ahead with intermittent fasting (4). Here are a few things about intermittent fasting that you should bear in mind if you are considering it while pregnant:

a) During the First Trimester

The first trimester is when most women tend to experience nausea and may even start to develop food aversion. This tends to happen at around six weeks to eight weeks. All this takes place due to the changing hormones as your body starts to prepare itself to grow and later give birth to your baby.

During the first trimester, your blood sugar tends to go down a bit, and your resistance to insulin will improve for a little while. Your pancreas, too, starts to grow, and so there is more insulin being produced by your body. It has been found that even women who have type 1 diabetes and do not produce insulin will have a drop in their insulin dosage during the first three months of pregnancy. It has been theorised that this could be a result of the expansion of the beta-cell during pregnancy. This may result in a little insulin being produced temporarily.

At this time, you will be hungry, but because of your food aversion and your nausea, you will not really feel like eating much. If you try to eat a large meal at one time, it may result in you throwing it all up later. Your only option to satiate your hunger without becoming sick is to have small snacks or meals whenever you are hungry.

A cracker, healthy oat cookies or a granola bar may be some simple things your body can retain at this time. These do not usually keep you satiated for long, so you will feel the need to eat again rather quickly. This is why you should make sure to have healthy snacks on hand.

It is important for you to eat well during your first trimester, especially since your food aversions may not allow you to eat protein or fat during certain times. Forcing your body to fast at these times may make you feel even sicker.

The only way that you can satiate your hunger without having to give in to the nausea is to eat when you are hungry. At times like this, intermittent fasting is just not possible.

b) During the Second Trimester

For some women, their nausea and food aversions may lessen at this point, and they can try to get into a regular eating pattern. Bear in mind that this is not true of everyone. Pregnant women need to focus on meeting their micronutrient needs. If you try to fast intermittently, it is going to reduce the opportunities you have to consume them.

There may be a few rare women who feel good when they eat only two meals a day during this time. If this is you, then you do not need to force yourself to eat more. As long as this is the pattern that your body naturally follows, there is nothing wrong with it.

When you are pregnant, however, you should never force your body to stop eating; rather, you should listen to it. Eat more if that is what you need. Just remember, all your meals should be balanced.

c) During the Third Trimester

During your third trimester, you will probably find it the hardest to try to eat within a given window. At this stage of your pregnancy, your baby is growing, and your belly will be pretty big. Your stomach can get quite compressed because of this. So, it becomes impossible to eat two large meals and forgo all other types of eating.

During your third trimester, your body will need around 2200 to 2600 calories per day. It is not possible for you to eat all that within the small window that you need when indulging in an intermittent fast. Your stomach will be too compressed to be able to digest the food.

Your body will need at least 73% more protein during late pregnancy. After all, you are growing another little human in your womb. Your insulin resistance is also quite high at this stage of pregnancy. The best option for women in their third trimester is to eat smaller meals throughout the day. It is extremely unwise to try an intermittent fast at this time. Speak to your doctor about the best diet for you during this trimester.

Risks of Doing Intermittent Fasting in Pregnancy

We have already learnt above that it is an unwise decision to indulge in intermittent fasting when you are pregnant. Here we discuss the impact of intermittent fasting on mom and baby:

• Intermittent fasting can lower the blood sugar of pregnant women too much. The blood pressure of women drops naturally during pregnancy, so when low blood pressure and blood sugar are combined, it can lead to fainting or light-headedness.
• Fasting women tend to have low glucose, and this means that there is less to share with their baby. This will result in lower foetal movement as your baby will not be getting the needed amount of nutrition (5).
• In a 2024 student thesis published by the University of Manchester, it was found that the timing of food intake restrictions and the amount of food eaten during pregnancy can negatively affect the cognitive abilities, behaviour, and neurochemistry of offspring in their later lives, even when maternal health and birth characteristics of the offspring seem to be unaffected (6).
• It could also reduce the neonatal birthweight without increasing the risk of low birthweight (7).

Intermittent fasting may be particularly risky in the following situations:

• High-risk pregnancy
• History of miscarriage
• Twin or multiple pregnancy
• Gestational diabetes
• Low blood pressure or anaemia
• Underweight pregnancy
• Severe nausea and vomiting

Can Intermittent Fasting Cause Miscarriage?

During pregnancy, the body needs a steady supply of nutrients, fluids, vitamins, and calories to support both the mother and the growing baby. This is why many women wonder whether fasting during pregnancy could increase the risk of miscarriage.

At present, there is limited scientific evidence directly proving that intermittent fasting causes miscarriage. However, healthcare experts generally advise pregnant women to avoid strict fasting routines unless medically supervised. The concern is less about fasting itself and more about the effects prolonged fasting can have on the body during pregnancy.

Overall, while intermittent fasting may not directly cause miscarriage in every case, pregnancy is generally not considered the ideal time for restrictive eating patterns. A balanced and regular diet is always the safest approach for both mother and baby.

What Kind of Intermittent Fast Diet Is Appropriate in Case a Pregnant Woman Chooses to Fast

Intermittent fasting for pregnancy is generally not recommended. If you are pregnant and still wish to fast for religious or personal reasons, it is safest to first consult a gynaecologist or nutritionist. They can help assess whether fasting is safe based on the stage of pregnancy and overall health condition.

You may try fasting for only 12 hours, particularly overnight. So, a 12-hour fast would look something like this: you eat from 7 am or 8 am until 7 pm or 8 pm. It is recommended to stick to a normal diet and avoid cutting anything out. This is especially true when it comes to cutting out anything essential or trying to squeeze too much into a short period of time. It is best to eat a little every few hours.

If you feel like this fast means that there is not much actual fasting going on, remember that while you are pregnant, it is still quite a task to avoid eating for those few hours before bed. You do not sleep for the entire 12 hours, so there actually is a little bit of a fast going on during the hours that you are awake.

Should You Stop Your Diet While Pregnant If You Were Doing It Before Pregnancy?

Yes, it is extremely important for you to have a regular diet while pregnant. This will help in maintaining your and your baby’s blood sugar and blood pressure. If the reason you were fasting intermittently was for weight loss, then you can actually switch your diet around. Rather than trying to lose weight, remember that you need to gain a few pounds during your pregnancy to remain healthy.

This may cause some alarm in some of you; after all, there is a chance you may gain too much weight. The key is not to lose or gain randomly, but to maintain a healthy weight for the trimester you are in. There may be times when you do need to lose only a little weight, and at others, when you need to gain some weight.

This will depend on you as an individual. Be sure to have this discussion with your doctor. Most of the time, you will need to cut out unhealthy foods such as processed foods, food that is high in sugar, carbonated drinks and others. A fresh and natural diet can work wonders when you are pregnant.

The new diet that you may have to follow to maintain a healthy weight during pregnancy is to widen the window for eating. This is a complete turnaround if you are used to intermittent fasting, but it is a healthier option for both you and your baby. The idea is not to binge eat during this entire time. Instead, you should focus on eating healthy food in smaller quantities. Stick to a more balanced diet, and you will be able to avoid putting on too much weight.

Intermittent fasting and pregnancy are not a match made in heaven. While it may be a great way to lose weight otherwise, you should always bear in mind that you are now responsible for another life. What you eat, or don’t eat, will affect your baby. Even how you eat and how much you eat are important.

The hormonal changes your body is going through are already going to affect your body, so rather than focusing on intermittent fasting, you should focus on eating right and following your doctor’s orders. Maintain the right weight during your respective stage in pregnancy, even if it is not the ideal weight you would like to be. The health of your baby is more important.

FAQs

1. Can intermittent fasting harm the baby during pregnancy?

Long fasting periods may reduce calorie and nutrient intake, which can affect the baby’s growth and development if not managed properly. Pregnant women generally need regular meals and hydration.

2. Is it safe to continue intermittent fasting if I was doing it before pregnancy?

Some women may continue modified fasting under medical supervision, but most doctors recommend stopping strict fasting routines during pregnancy because nutritional needs increase.

3. Can fasting during pregnancy cause dizziness or weakness?

Yes, fasting can sometimes lead to low blood sugar, dehydration, headaches, fatigue, and dizziness during pregnancy, especially in the first trimester.

4. Can pregnant women fast during religious occasions?

Fasting is not safe during pregnancy. However, several women do it for religious purposes. It is safest to consult a doctor first, especially if there are concerns like anaemia, gestational diabetes, or low blood pressure.

5. What is a safer alternative to intermittent fasting during pregnancy?

Instead of fasting, doctors often recommend balanced portion control, healthy snacks, and mindful eating to maintain a healthy weight gain during pregnancy.

If you are looking into intermittent fasting for religious purposes, speak with your respective religious elder. In most religions, women are not compelled to fast when pregnant.

Remember, each woman is different, and not all women experience the same symptoms during pregnancy. This makes it even more important to have a discussion with your doctor about any changes that you want to make during pregnancy. Whether it is about a new diet or fast, or whether it is a new exercise, your doctor will know what is right for you to do in order to keep your baby healthy.

Also Read:

Fasting In Pregnancy
Over Eating In Pregnancy
Foods to Avoid While Pregnant
Vegetables to Eat & Avoid During Pregnancy

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Sources References

1. National Library of Medicine – Intermittent fasting: the science of going without

2. Cell Press – A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan

3. National Library of Medicine – Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma

4. Cleveland Clinic – What Is Intermittent Fasting?

5. Taylor & Francis Online – The effect of intermittent maternal fasting on human fetal breathing movements

6. The University of Manchester – Impact of Maternal Intermittent Fasting during Pregnancy on Offspring Cognitive Development and Function in Rat

7. MDPI – Intermittent Fasting During Pregnancy and Neonatal Birth Weight: A Systematic Review and Meta-Analysis