One of the most popular questions I’ve been getting on Instagram is about Intermittent Fasting and nursing aka breastfeeding. People want to know first, if I’m doing IF, second, if I’m still nursing and lastly, if I’ve noticed a drop in my supply. 

Short answer is no, I have not noticed a drop in my milk since starting a 16:8 Intermittent Fasting routine at 6 months postpartum 2.5 weeks into trying it out.

The program that I’m doing does not have me decreasing my calories much more than what I was eating before (around 2000). Really the only change is that I’m eating within an 8 hour window. If I were to wake up starving, you bet I would eat but I haven’t been there yet. I’m also now making sure I hit a goal of 100 grams of protein a day by tracking my macros.

I’m currently on day 4 of week 3 of the Faster Way To Fat Loss program. See my initial thoughts here.

What is Intermittent Fasting?

IF has grown in popularity over the past few years and can be done a variety of ways. Basically you restrict the window in which you eat so that your body can rest, burn fat and function optimally.

Some programs suggest a 5:2 fasting program which means you “fast” 2 days a week (eating around 500 calories or 25% of daily calories consumed) and then eat regular (around 2000-2500 for most people) calories the other 5 days, alternate day fasting similar to above numbers or time restricted which is what i’m doing where I eat during an 8 hour window and “fast” during 16 hours, 8 of which I’m hopefully sleeping. You don’t have to do a 16:8 window, you can do a 14:10 or even 12:12! The idea is to give your body a rest from constantly working to convert food into energy.

Remember when Oprah said to stop eating at 6 pm? That was basically IF back in the day.

Many people swear by intermittent fasting to decrease body fat, increase energy and focus, assist in detoxification, slow down the aging process, and even protect them against chronic disease.  In fact, there is evidence to suggest that intermittent fasting can decrease the risk of certain diseases such as type 2 diabetes, cardiovascular disease, and even cancer.

The top results via google if you currently search breastfeeding and intermittent fasting produce quotes from doctors who caution against doing it. However, the articles read like the doctors think you’re going on some sort of juice cleanse where calories are seriously restricted and rarely differentiate between time restricted fasting like a 16:8 window without calorie restriction vs alternate day or whole day fasting.

“Intermittent fasting can be dangerous during breastfeeding because it restricts the amount of food and fluids for both mom and baby,” Armul says. “Breastfeeding requires a continuous source of fluids and calories to maintain a woman’s milk supply and meet her own body’s needs. Limiting food and fluids from any type of fasting can lead to reduced milk supply, inadequate nutritional status, low energy levels and dehydration.” [Women’s Health]

Harvard University agrees. On their health science blog, the team wrote that, “A systematic review of 40 studies found that intermittent fasting was effective for weight loss, with a typical loss of 7 to 11 pounds over 10 weeks,” but that women who are pregnant or breastfeeding should avoid this diet. They wrote that there just isn’t enough evidence as to the efficacy of this plan, and it’s not worth the risk. [Romper]

The Harvard article if you read it however was based on 3 different fasting cycles including alternate day fasting, whole day fasting and also time restricted. I would never recommend whole day fasting or alternate day fasting to someone nursing. I would never recommend IF to pregnant women ever at all. The studies feel broad which is why I wanted to share my own experience breastfeeding and intermittent fasting.

Per the advice above, I also would NOT recommend doing intermittent fasting until your supply is well established and some solid food has been introduced which means, I’d recommend waiting at least 4 months postpartum maybe even 6+ depending on your sensitivity to a program. 

The program that I’m doing has this blog post that suggests it’s OK to do IF while nursing and modifications to take.

Some people have asked, aren’t you starving in the morning while intermittent fasting? 

I’m honestly not. I took a week to practice pushing back the time when I ate breakfast. I think the reason I’m not starving is because I’m eating a balanced ratio of macronutrients and nutrient dense foods. My target macros according to the program are 50% carbs, 30% fats and 20% protein (this is the standard MyFitnessPal recommendation actually). I always hit my fat goal because I love nuts, olives, nut butter, avocado, etc but I struggle to hit my carbs and protein unless I plan out my meals.

I’m also making sure that I drink plenty of fluids.

I will admit that Connor doesn’t take bottles currently so I don’t pump often which means I don’t know how much milk I produce to begin with. All I know if that I have a healthy, happy and fat baby boy. He is starting to eat solids now too so naturally my milk supply will begin to be reduced.

This is my personal experience. I have not measured or weighed myself to know if I’ve lost weight yet!

This is not a scientific study. There actually haven’t been a lot of studies about women and their hormones when it comes to IF. I would not have attempted to do IF or any fat loss program before 5-6 month postpartum because I didn’t feel ready. I do not believe in dieting or restricting calories while nursing. I do not feel like I’m restricting calories on this program, I’m just choosing not to go to Flour at 4 pm and buy a couple of cookies to get me to 7 pm.

Intermittent Fasting and Female Hormones

If you were to google intermittent fasting and women’s hormones, you would find a variety of blog post from respected and shady sources that conflict each other. So I did what any good blogger does, I asked my Instagram followers to share their own personal stories (lol). I do have a variety of medical professionals who follow me but also was curious what my peers’ doctors were saying.

Two things that seem to remain consistent is that IF causes hormone dysregulation and irregular periods for women.

Most research however points to IF causing a woman’s hormones to go out of whack also causing her fertile window to be a bit unpredictable. So if you’re trying to get pregnant and looking to pinpoint ovulation, IF probably isn’t for you. 

I did not get my period after Tommy was born for 18 months. I nursed him for 10 minutes in the morning for about 2 months before stopping at 18 months and got my period that month. I have not gotten my period back yet after Connor and don’t expect to until I totally stop nursing again so I can’t share my experience about this.

Beyond reporting biases in the blogosphere, there remains an even greater problem of a significant testing bias in the fasting literature. Searching “men” + “intermittent fasting” in a Harvard article database yields 71 peer-reviewed articles. Searching “intermittent fasting women” yields 13, none of which are a) solely about women b) controlled studies or c) about more than body weight or cardiovascular benefits. [Paleo for Women ]

So basically, there isn’t a ton to go off of here but here are results from a study using female rats:

Any degree of nutritional stress (fasting or mere caloric restriction) causes increased wakefulness (during the day, when they normally sleep), better cognition (for finding food), hyper alertness, and more energy. In short, female rats become better at finding and acquiring food when they fast, as if their bodies aren’t as well-equipped to deal with the stress of going without food. They also become less fertile, while the males actually become hornier and more fertile (probably to account for the females’ plummeting fertility). Ovary size drops (bad for fertility), adrenal gland size increases (which in rats indicates exposure to chronic stress), and menstrual cycles begin to dysregulate in proportion to the degree of caloric restriction. MARKS DAILY APPLE

However, I was shocked to learn a few doctors recommended their patients try a keto diet as well as intermittent fasting to get pregnant! I found this article on how a keto diet could benefit women looking to get pregnant with PCOS. I cannot vouch for it but thought it was worth sharing.

Other research (from a Pro IF website) has shown that women who practice IF have healthy eggs longer in life than women who don’t which is an argument for IF in preserving fertility. So if you want kids later in life, maybe IF is for you. Read more about this study here.

I do like this closing thought from Mark’s Daily Apple blog post, “Instead of aiming for the longest fast you can tolerate, aim for the shortest fast that gives results. Don’t try to power through a 24 hour fast, braving headaches and foggy thinking and overpowering hunger. Do try eating dinner earlier so you get a good 12 hours of “fasting” simply by going to bed and eating breakfast at a normal time.”

So there you have it. My experience intermittent fasting for the past 2.5 weeks while nursing at 6 months postpartum as well as some thinking points regarding IF during your fertile years if you’re thinking of having (more) children.

Would love to hear your thoughts below.

This isn’t meant to be a PRO or ANTI intermittent fasting but rather my experience as well as some expert opinions that don’t really seem to be based on a ton of research dedicated to just women. It’s hard to do studies using pregnant or nursing women for obvious reasons so I find it helpful to try to get as many opinions and experiences to formulate my own position.