This article is reviewed by a team of registered dietitians and medical doctors with extensive, practical clinical and public health experience.
Intermittent Fasting While Pregnant: Is It Safe During Pregnancy?
If you have a baby on the way or you’re considering expanding your family soon, chances are you are already considering your little one’s health and nutrition. And since your baby’s nutrition depends on your own nutritional intake during pregnancy, you may be considering various diet changes. Intermittent fasting (IF) has gained wide popularity in today’s diet culture, but can you safely meet your pregnancy needs while practicing intermittent fasting? The short answer: no, the risk factors outweigh IF’s purported benefits while pregnant.
This article carefully explores intermittent fasting’s supposed benefits and their relationship to pregnancy.
Can You Do Intermittent Fasting While Pregnant?
Pregnancy produces many changes in the body, and it requires many lifestyle changes. For example, the eating habits that once worked before pregnancy do not necessarily meet your needs during the nine months your body meticulously grows your baby.
Research on intermittent fasting during pregnancy is limited at best. Unlike a diet that focuses on calorie restriction, IF requires you to eat all your calories within a specific time frame each day. For example, the 16/8 fasting method allows you to eat during an eight-hour window but forbids you to eat during the other 16 hours of the day.
Religious intermittent fasting has long been a staple in many faiths. However, in some religions, pregnant women are exempt from fasting to reduce the risks associated with inadequate nutritional intake during pregnancy. One compelling study found that the risk of preterm birth was increased by 35% for pregnant women who fasted during Ramadan in their second trimester.
Outside of religious reasons, many people follow a fasting diet to lose weight. However, losing weight is not recommended during pregnancy. In fact, the recommended healthy weight gain during pregnancy ranges from 11 to 40 pounds, depending on your BMI before pregnancy.
It is important to remember that weight gain is essential to many aspects of healthy pregnancies. Your baby might weigh seven or eight pounds, but the rest of your weight gain during pregnancy can be found in your increased blood volume, increased fluid volume, larger uterus, and the placenta and amniotic fluid. All of these factors are key to supporting maternal health and the baby’s growth in utero.
Eating a balanced diet is vital to meeting your body’s and your baby’s needs. Science says the average pregnant woman needs approximately 300 additional calories each day to support her pregnancy. The number doubles for those women who are pregnant with twins. Enforcing fasting windows only increases the difficulty of meeting those additional needs.
Is Intermittent Fasting Safe For You to Do While Pregnant?
The limited research available so far suggests that intermittent fasting can help support weight loss, control blood sugar, reduce inflammation, and reduce the risk for cardiovascular disease in the average person. However, research is especially lacking when it comes to intermittent fasting and women’s health, specifically pregnant women’s health.
While IF doesn’t restrict your eating and calorie intake, it does dictate when you are allowed to eat. Based on what we know to be true about nutrition during pregnancy, we can say that this eating pattern is not recommended for pregnant women. Even without restricted calorie intake, you will naturally consume fewer calories by limiting yourself to a small eating window each day. Fasting windows may vary based on the type of IF diet you follow, but with your body’s changing needs during pregnancy, a forced time restriction of any kind is not ideal.
Every pregnancy is unique, and no two women experience the same symptoms or changes. Unintentional periods of fasting may arise with bouts of morning sickness, but these typically don’t raise significant concern. However, nutrient deficiencies and dehydration may develop if these follow periods of fasting while on an IF diet.
Furthermore, IF puts pregnant women at increased risk for low blood sugar. A pregnant woman’s blood sugar plays a significant role in both her health and her baby’s health. If a woman develops gestational diabetes, she is at risk for high blood pressure, preterm delivery, and developing type 2 diabetes in the future. On the other hand, if you have consistently low blood sugar, you may notice lightheadedness or even a decrease in fetal movement. Low blood sugar is common during intermittent fasting because even if your energy stores are depleted, you cannot eat during a fasting period.
Downsides of Intermittent Fasting During Pregnancy
Intermittent fasting is often advertised as a lifestyle weight loss tool in today’s diet culture. While it can help people lose weight, control glucose levels, and possibly help treat certain chronic diseases, it is very difficult to maintain long-term and may have a negative impact on other areas of life. During pregnancy, intermittent fasting can take a toll on the mother-to-be’s mental and physical health.
Pregnancy requires lifestyle changes that may make you feel distant from your normal routine. You may not have the energy to go on your favorite hikes with friends, or maybe you can’t eat at your favorite sushi restaurant. You probably don’t even feel comfortable in your own bed anymore. IF stands to further limit your connection to your pre-pregnancy life by limiting your nutritional intake and social agenda. If your friends want to catch up over dinner, better make sure it’s not during a planned fast.
Intermittent fasting can also negatively affect your breast milk supply. Sometimes referred to as the “fourth trimester,” the time soon after giving birth requires quality nutrition to heal your body and support breast milk production if you choose to breastfeed. However, without adequate calorie, protein, and fat intake, breastfeeding women will see their milk supply suffer.
Furthermore, IF may negatively impact fertility. For those who are underweight prior to pregnancy, IF may lead to further weight loss or prevent the needed increase in weight. Underweight women have lower production of estrogen, leading to irregular menstrual cycles and potential difficulty getting pregnant.
Pregnancy Safe Alternatives
It is always important to discuss your pregnancy nutrition needs with your physician or dietitian, but following a well-balanced diet rich in whole grains, fruits, vegetables, and lean proteins is a great place to start. It is essential to supply your body with the nutrients it needs during this incredible time of growth and change, and you are your best advocate.
Rather than limiting yourself to a small eating window, it is important to listen to your body’s needs and eat when you’re able. Hunger cues signal a need within your body, and it’s important to address those needs, not just for yourself but also for your baby.
Along with a more balanced diet, exercise is another way to support a healthy pregnancy. With your doctor’s approval, avoid restricting calories and focus on logging about 30 minutes of moderate activity each day. Exercise has been shown to help control blood sugar and support healthy, gradual weight gain during pregnancy.
Limited research suggests that intermittent fasting may benefit metabolism and help control blood sugar, lower blood pressure, and prevent heart disease. However, eating patterns that restrict calorie intake and increase the risk of deficiencies in essential nutrients actually actively work against a healthy pregnancy.
Most pregnant women can trust their instinct when it comes to eating a balanced diet. Your body is actively trying to gain weight to support your pregnancy, so weight loss is not recommended. In addition to their normal intake, pregnant women should consume approximately 300 additional calories each day to fuel their body’s increased demand for energy.
Overall, nutrition during pregnancy is extremely individualized, so it’s important to discuss it with your doctor or dietitian before making any lifestyle changes.
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- Tith, R.M., Bilodeau-Bertrand, M., Lee, G.E., Healy-Profitós, J. and Auger, N. (2019). Fasting during Ramadan Increases Risk of Very Preterm Birth among Arabic-Speaking Women. The Journal of Nutrition, [online] 149(10), pp.1826–1832. Available at: https://academic.oup.com/jn/article/149/10/1826/5518964?login=false
- Anon, (2022). Weight Gain During Pregnancy. [online] Available at: https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pregnancy-weight-gain.htm#weight
- Longo, Valter D. and Mattson, Mark P. (2014). Fasting: Molecular Mechanisms and Clinical Applications. Cell Metabolism, [online] 19(2), pp.181–192. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3946160/