Many new mothers are eager to return to their pre-pregnancy weight after giving birth. While breastfeeding can aid in weight loss for some, others may explore alternative methods like intermittent fasting. This article examines the safety of intermittent fasting while breastfeeding, considering its potential effects on milk supply, nutrient composition, and overall maternal and infant health.
What is Intermittent Fasting?
Intermittent fasting (IF) is an eating pattern that involves cycling between periods of eating and voluntary fasting on a regular schedule. Instead of spreading meals and snacks throughout the day, individuals following IF consume their food within a specific window of time. There are various approaches to IF, including daily eating with extended nighttime fasting, or alternating between regular eating days and days with restricted calorie intake.
Some people believe cells may resist disease when they’re under stress from not eating. Studies suggest fasting may reduce inflammation in the body, as well as blood sugar, blood pressure, and cholesterol levels. IF can also promote weight loss by tapping into fat stores for energy and reducing overall calorie consumption. For example, one study showed that adults practicing alternate-day fasting lost an average of 8 percent of their body weight in 8 weeks.
Potential Risks of Intermittent Fasting While Breastfeeding
While intermittent fasting has gained popularity as a weight management strategy, its suitability for breastfeeding mothers requires careful consideration. Breastfeeding increases a woman's energy needs, and restricting food intake through fasting may pose risks to both the mother and the infant.
Impact on Milk Supply
Breast-milk production depends on frequent emptying of the breast plus adequate maternal calories, protein, and fluids. Skipping meals for long stretches can lower prolactin and reduce daily caloric intake below what’s needed for stable milk output. Clinical lactation studies show that mothers consuming fewer than 1,800 kcal/day produce 15-20 % less milk by the next day.
Read also: Breaking the IF Plateau
Traditional advice surrounding nutrition in breastfeeding explains that women need an additional 330 to 600 calories a day to support milk production. Eating enough - and enough of the right foods - ensures that you stay healthy and that your milk contains enough of what your baby needs to thrive.
Low calorie diets and gaps in nutrition - or in fluid intake - may suppress milk production. If this occurs, it can take some work getting your milk supply back up to levels that support your growing baby.
Changes in Breast Milk Composition
Current research suggests that fasting doesn’t necessarily impact the macronutrients in breast milk. However, some micronutrients in breast milk may be “significantly” affected. In women fasting for Ramadan, one study showed that milk output stayed the same before and during fasting. What changed, though, was the concentration of lactose, potassium, and the milk’s overall nutrient content.
Electrolyte and sugar levels shift during daylight-hour fasts. La Leche League Canada reports Ramadan studies showing higher breast-milk sodium and calcium and lower phosphorus and lactose when mothers abstained from food and drink from dawn to sunset, indicating quality changes even without volume loss.
Trace minerals such as zinc and magnesium drop after 24-hour fasts. A review on KellyMom highlights research where single-day fasts led to measurable declines in breast-milk zinc, magnesium, and potassium, suggesting intermittent fasting can reduce micronutrient density available to the infant.
Read also: Choosing a Diet: Keto or Fasting
Some experts share that low food intake while breastfeeding may negatively impact the nutrients your baby gets in your milk, specifically iron, iodine and vitamin B-12. It may take some hard work to ensure you’re getting enough nutrients on the daily.
Maternal Health Concerns
If your nutrition is impacted enough to change the composition of your milk and lower your milk supply, this may also have implications for your own health as well. Nutritional gaps can lead to things like vitamin deficiency anemia. Symptoms include anything from fatigue and shortness of breath to weight loss and muscle weakness.
Ketoacidosis is a dangerous, life-threatening complication, with very high levels of ketones making your blood acidic. Symptoms of ketoacidosis include nausea, vomiting, abdominal pain, shortness of breath, and headache. If you get any of these symptoms while restricting your food intake, it’s vital to seek medical help immediately.
Risks to the Infant
Changes in breast milk composition aren’t necessarily good for baby. Researchers who focused on this topic concluded that women should work closely with their healthcare providers when it comes to fasting and its potential risks.
It's important to note that no two women are the same. The way fasting may impact nutrients in breast milk and the overall supply of milk may be considerably different depending on the individual.
Read also: The Truth About Diet Soda and Fasting
Pro-breastfeeding group La Leche League outlines a few things that may indicate there’s an issue:
- Your baby is lethargic or overly sleepy.
- Your baby either takes too much or too little time at the breast.
- Your baby isn’t pooping enough.
- Your baby is dehydrated. You may notice diapers are dry or you might see dark or reddish-brown urine in his diaper.
- Your baby isn’t gaining weight or staying on their growth curve.
When Intermittent Fasting Might Be Considered
In the later stages of breastfeeding, when your baby has begun to eat other foods, intermittent fasting may be safe to try. If you’re just breastfeeding in the morning and evening and you’re not the primary source of your baby’s nutrition anymore, then you could probably incorporate some fasting toward the very tail end of that breastfeeding period.
Safer Approaches to Postpartum Weight Loss
Doctors recommend aiming to lose slowly and steadily, no more than around a pound a week. You’ve probably heard that it took 9 months to grow your baby (and put on the weight) and that it will take 9 (or more) to lose it. Be gentle with yourself. Growing and birthing a baby is an incredible feat.
Dietary Adjustments
Instead of trying intermittent fasting, fill up on a healthy breastfeeding diet. A healthy breastfeeding diet should incorporate a variety of nutritious whole foods, including those that can help you maintain your energy and even increase your milk supply. Turn to staples of the Mediterranean diet, like:
- Whole grains
- Leafy greens
- Lean proteins like salmon, grass-fed beef and eggs
- Beans and lentils
- Nuts and seeds
- Greek yogurt
This may mean making some small tweaks to your daily routine, like:
- Serving your meals on smaller plates to cut portion sizes.
- Skipping processed foods, especially those high in sugar and fat.
- Slowing down your eating process to allow your brain to catch up to your stomach’s fullness signals.
- Eating whole foods, like fresh fruits, vegetables, and whole grains.
Exercise
Increasing your weekly exercise to the recommended 150 minutes of moderate activity (like walking or swimming) or 75 minutes of vigorous activity (like running or Zumba). Add strength training to your workout twice a week with either weight machines, free weights, or body weight workouts.
Guidelines for Safer Fasting During Lactation
If you and your clinician decide a mild fasting protocol is acceptable, precise planning preserves nutrition and supply. Set a 12-14-hour overnight fast only. A 7 pm-7 am or 8 pm-10 am window lets you sleep through most of the fast and still eat three nutrient-dense meals.
- Aim for 500 kcal above pre-pregnancy needs. A 160-lb woman usually requires 2,300-2,500 kcal while breastfeeding; track intake with a food log for the first two weeks.
- Include 20 g protein in every meal. Eggs, Greek yogurt, lentils, and salmon support milk protein synthesis and maternal muscle recovery.
- Drink 8-10 oz of fluid every time you nurse. This simple cue guarantees the 2-3 L daily hydration target.
- Monitor diapers and weight weekly. 6+ wet diapers/day and infant weight gain of 5-7 oz/week confirm adequate milk despite fasting.
- Pause fasting if you feel dizzy, nauseated, or see slower infant gain. Stop the fast immediately if the mother develops dizziness, nausea or stomach upset, or if the baby’s weight gain falters during the trial period.
Medical Monitoring
Blood work helps catch deficiencies early. Medications and supplements may need timing adjustments to avoid fasting periods.
- Check ferritin and vitamin B12 every 3 months. Lactating women lose iron into milk; fasting can further limit intake, risking anemia.
- Screen thyroid-stimulating hormone (TSH) if fatigue worsens. Postpartum thyroiditis affects up to 5 % of mothers; calorie restriction can mask symptoms.
- Time prenatal vitamins with the first meal. Fat-soluble vitamins A, D, E, K absorb 30 % better when taken with dietary fat, improving breast-milk micronutrient content.
- Avoid weight-loss medications during active breastfeeding.