Is Intermittent Fasting When Breastfeeding Safe?

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Most mothers would aim to lose the extra weight they gained during pregnancy right after delivery. One method they may consider is intermittent fasting during postpartum. However, intermittent fasting while breastfeeding should be carried out while considering the baby’s health. Fasting may affect the milk’s composition and supply. Hence mothers should be aware of the side effects of it.

This post will help you learn about intermittent fasting during breastfeeding and its safety for mother and baby.

What Is Intermittent Fasting?

Intermittent fasting is an eating pattern where you eat at specific times and fast for specific periods. Since meals interject your fasting, it is called intermittent fasting (1). Most intermittent fasting patterns have no restriction on water intake, although caloric drinks, such as drinks with sugar, milk, and other beverages with calories, are restricted and should be consumed with meals.

Research indicates that intermittent fasting may benefit overall health since it encourages the body to tap into its fat reserves due to fewer calories received from food (2). Therefore, it is quite popular among individuals who desire to lose weight, including lactating mothers who wish to lose the extra weight they gained over pregnancy.

There are various intermittent fasting patterns, including those where you do not fast entirely and only restrict your calorie intake significantly. Below are some of the most common ones (3).

  1. The 16/8 technique entails fasting for 16 hours per day and curtailing the daily consumption window to eight hours.
  2. The 5:2 diet involves eating about 500 calories a day for two days a week and have a regular diet for the remaining five days.
  3. Alternate day fasting involves reducing your calorie intake to 500 calories every alternate day.
  4. A 24-hour fast is when you fast for a day or 24 hours for any two non-consecutive days a week.

Is Intermittent Fasting Safe For The Mother?

Exclusively breastfeeding mothers usually use up an average of 500 extra calories per day to maintain a full milk supply. There is insufficient research to conclude the benefits or detrimental effects of intermittent fasting on the breastfeeding mother. The type of intermittent fasting pattern chosen may determine the effect of intermittent fasting on the mother’s health, her breast milk production, and the breast milk supply (4).

According to a few studies, below are some of the potential side effects of intermittent fasting on lactating mothers (5).

  • 24-hour fasting without water intake may bring an imbalance in the concentration of electrolytes in the milk with a drop in the milk’s potassium levels.
  • 24-hour fasting may affect the fat content of the milk, and there could be a drop in the number of triglycerides.
  • Some mothers may be at an increased risk of hypoglycemia (low blood sugar), which may interfere with their ability to breastfeed their baby.
  • Some mothers may notice a drop in their breast milk supply.

Is Maternal Intermittent Fasting Safe For Babies?

There is inadequate research into the effects of maternal intermittent fasting on breastfeeding babies. The effects may vary based on the type of intermittent fasting pattern chosen and the baby’s health.

According to a few studies, below are some of the potential side effects of maternal intermittent fasting on breastfeeding babies (6). 

  • A decline in breast milk’s nutritional composition due to a 24-hour fast may cause the baby to receive insufficient nutrients than the recommended daily intake.
  • Fasting for several hours may reduce the concentration of micronutrients, such as zinc and magnesium, in the milk. These micronutrients are vital for several functions, such as maintaining immunity.
  • Frequent intermittent fasting may affect the milk supply, affecting the baby’s regular feeding pattern. The baby may demand more milk at odd times since they receive insufficient milk during each feed.

Intermittent Fasting Factors That Could Affect Breastfeeding

Since there is no conclusive evidence, the effects of maternal intermittent fasting on the mother and baby may depend on various factors. Below are the key factors that may influence how you or your baby reacts to intermittent fasting.

  • Period of intermittent fasting. A 24-hour fast is more likely to have side effects for you and your baby than limiting calorie intake to 500 calories twice a week.
  • Extent of dietary restrictions. Intermittent fasting with restricted water intake is more likely to affect breast milk composition and supply. 
  • Type of food eaten. If you eat dietary supplements or a balanced meal, it may replenish all the nutrients lost during fasting, causing little to no effect on your breast milk composition. 
  • Overall health of the mother. If you are already losing postpartum weight through breastfeeding and exercise, intermittent fasting may not be very helpful. 
  • Presence of health problems in the mother or baby. Intermittent fasting is not safe for you or your baby if any of you have a health condition such as diabetes Or if your baby has iron-deficiency anemia, intermittent fasting may not be advisable since you will need to maintain adequate iron levels in the breast milk.
  • Sensitivity of the baby to milk supply or quality. Some babies could be more sensitive to the milk’s composition and supply, causing them to be easily affected by maternal intermittent fasting.
  • Exclusively breastfed or formula-fed baby. Exclusively breastfed babies may be more easily affected by changes in milk composition due to intermittent fasting than babies who also receive nourishment from formula. 
  • Medications taken by mother or baby. Some medicines may affect breast milk composition, and when coupled with intermittent fasting, it could significantly change its nutrient content. Babies on medication may require frequent feeding, which may not be possible if the mother is fasting intermittently.

How To Safely Fast During Lactation?

Healthcare experts recommend that you consult a doctor before trying any form of intermittent fasting during lactation (7). Intermittent fasting is usually not recommended for lactating mothers, but you may try it under a doctor’s supervision (8).

Below are some points to keep in mind before and during intermittent fasting while breastfeeding.

  • Consider your baby’s age and whether they are exclusively breastfed. Breast milk is the only source of nutrients and fluids for exclusively breastfed infants younger than six months. If that is the case with your baby, wait until they are six months old to begin intermittent fasting.
  • Pick the least intense type of intermittent fasting, such as the 16/8 technique or 5:2 diet, where you may still be able to eat adequate food during your waking hours.
  • Do not pick any intermittent fasting technique where you may have to restrict water intake. Inadequate water intake may negatively affect your body’s water content, affecting your breast milk supply eventually.
  • Eat balanced meals with adequate nutrients to maintain the nutritional composition of your breast milk.
  • You must continue to take any supplements prescribed by the doctor and should not cut them down during fasting.
  • Some medications may require you to have an empty stomach for too long. If you are on any medication, discuss your intermittent fasting with the doctor.
  • If you notice any changes in the baby’s feeding patterns, growth, diaper-soiling patterns, and overall health, stop intermittent fasting immediately.

In most cases, breastfeeding alone may help you lose postpartum weight without the need for intermittent fasting. There are also several ways to lose postpartum weight naturally without fasting, and you may read about it here.

Frequently Asked Questions

1. When can I resume intermittent fasting after pregnancy?

Since fasting while breastfeeding can compromise your and your baby’s well-being, you can resume intermittent fasting once your baby has been completely weaned and solely relies on solids for nutrition (9).

2. Can I eat anything during intermittent fasting?

You should consume various healthy, nutritious foods during the eight-hour eating period. However, if you are pregnant or breastfeeding, avoid intermittent fasting to prevent complications (1).

The need to lose that extra pregnancy weight and get back to your pre-pregnancy body may prompt you to try intermittent fasting while breastfeeding. Intermittent fasting may prevent you from the adequate intake of nutrients for yourself and your baby since it can affect the milk supply and its composition. So, instead, you may try other alternatives for losing weight and getting fit by talking with your healthcare provider. However, if you choose to carry out intermittent fasting while breastfeeding, consult your doctor to know about the right way and also consider your baby’s age and health.

Key Pointers

  • The safety of intermittent fasting while breastfeeding depends on the type of fasting pattern.
  • Intermittent fasting while breastfeeding may cause electrolyte imbalance in the milk and increase the risk of maternal hypoglycemia.
  • It may also affect the baby’s feeding pattern.
  • Consult your physician before committing to intermittent fasting while breastfeeding.


MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
1. Intermittent Fasting: What is it, and how does it work?; John Hopkins Medicine
2. What is intermittent fasting?; Intermountain Healthcare
3. Intermittent Fasting: 4 Different Types Explained; Cleveland Clinic
4. Alessandra N. Bazzano et al., How do pregnant and lactating women, and young children, experience religious food restriction at the community level?; U.S. National Library of Medicine
5. Deena R. Zimmerman et al., Effect of a 24+ Hour Fast on Breast Milk Composition; Pennsylvania State University
6. Neslisah Rakicioglu et al., The effect of Ramadan on maternal nutrition and composition of breast milk; U.S. National Library of Medicine
7. Jane Racey Gleeson, Intermittent Fasting: Is it Right for You?; University of Michigan
8. Diet Review: Intermittent Fasting for Weight Loss; Harvard T.H. Chan School of Public Health
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Swati Patwal

Swati Patwal is a clinical nutritionist, a Certified Diabetes Educator (CDE) and a toddler mom with over eight years of experience in diverse fields of nutrition. She started her career as a CSR project coordinator for a healthy eating and active lifestyle project catering to school children. Then she worked as a nutrition faculty and clinical nutrition coach in different... more

Regina Kincaid

Regina qualified as a midwife in 2005 in Germany and has since worked in maternity care in England and Ireland. She achieved stage 1 of the UNICEF Baby Friendly accreditation as infant feeding lead midwife at Ealing Hospital in London and worked in the lactation team of the National Maternity Hospital in Dublin, Ireland. She did her Neonatal Examination Course... more