The Risks of Fasting During Pregnancy

Intermittent fasting is one of the most popular dietary protocols today. However, fasting during pregnancy isn't recommended. Here are the reasons why.
The Risks of Fasting During Pregnancy
Saúl Sánchez Arias

Reviewed and approved by the nutritionist Saúl Sánchez Arias.

Last update: 16 December, 2022

Intermittent fasting is one of the most popular dietary protocols in nutrition today. It contributes to stimulating weight loss and improves many parameters related to a person’s health status. However, fasting during pregnancy is not recommended during pregnancy and breastfeeding. It could be risky.

The first thing to be clear about is that fasting is a restrictive protocol. Although it’s not comparable to miracle diets or conventional hypocaloric diets, it ends up producing a reduction in intake in most cases, which is limiting in certain situations.

Fasting during pregnancy increases the risk of deficits

During pregnancy, nutritional requirements are increased. Not only is it necessary to meet the energy demands of the mother, but also those of the developing fetus. For this reason, it doesn’t make sense to apply a mechanism aimed at creating a hypocaloric environment, as this could limit the growth of the fetus.

At the same time, reducing the number of meals throughout the day can lead to certain nutritional deficits. At least this happens if the diet isn’t properly adjusted. Although not meeting the requirements is harmful under any circumstances, the effects are worse during the gestation period.

An inadequate intake of certain micronutrients could negatively affect the health of the fetus, making it more likely to develop diseases in the medium term. For example, consuming an optimal amount of omega-3 fatty acids on a daily basis is a determining factor in limiting the risk of autism and other neurological diseases. This is evidenced by a study published in the International Journal of Molecular Sciences.

The main risks of fasting during pregnancy

The main risks of implementing a fasting protocol in pregnancy are as follows:

  • Low birth weight. It’s related to insufficient energy and nutrient intake, which affects the development of vital organs.
  • Cognitive impairment. Dietary restrictions during the gestation period could alter the hormonal balance, favoring cognitive impairment in children or other problems related to neurological functioning.

Fasting and gestational diabetes

Intermittent fasting has been shown to be positive in improving the management of both type 1 and type 2 diabetes. Therefore, one might think that it may be useful in the case of women who’ve developed gestational diabetes. But the truth is that there are no studies that assess its effectiveness or safety.

In these cases, it’s best to follow a diet with little presence of simple sugars, including carbohydrates through complex sugars and foods with fiber. It’s also advisable to limit trans fatty acids and all kinds of ultra-processed industrial foods, prioritizing the consumption of fresh products.

In addition, as much as possible, it’s important to ensure regular physical activity, adapted to the limitations of the pregnant woman. These strategies will ensure effective control of blood glucose levels, preventing the fetus from suffering or experiencing alterations in the state of health.

Fasting during pregnancy in women who are overweight

Women who are overweight prior to pregnancy usually experience a lower mass gain during the gestation period. In this case, energy needs may not be increased during the first months, as there are reserves to meet the demands.

However, it’s not advisable to consider a fasting protocol in this case either. Although from the energetic point of view, there’s not going to be a significant deficit, it’s still necessary to cover the requirements of essential micronutrients. To do this, it’s best to implement a 3 or 5-meal plan, as there are no reservoirs in the body of all of them.

In addition, the demand for certain vitamins and minerals is increased during the period of pregnancy. An example would be the case of folic acid, whose deficit can generate problems in the neural development of the fetus.

Intermittent fasting is one of the best dietary protocols to promote a good state of health. However, it shouldn’t be practiced during pregnancy. At this time, it’s essential to ensure a continuous supply of nutrients, and all mechanisms that lead to their restriction should be avoided.

The best thing to do during pregnancy is to have a varied and balanced diet with a predominance of fresh foods as opposed to ultra-processed industrial foods. This will help to prevent complications, such as gestational diabetes. In addition, it will be necessary to supplement with certain nutrients, such as folic acid, to avoid health problems in the fetus.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Agostoni, C., Nobile, M., Ciappolino, V., Delvecchio, G., Tesei, A., Turolo, S., Crippa, A., Mazzocchi, A., Altamura, C. A., & Brambilla, P. (2017). The Role of Omega-3 Fatty Acids in Developmental Psychopathology: A Systematic Review on Early Psychosis, Autism, and ADHD. International journal of molecular sciences18(12), 2608.
  • Grajower, M. M., & Horne, B. D. (2019). Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients11(4), 873.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.