5 Reasons you are not Losing Weight While Breastfeeding

Ask any new or expecting mom why they plan on breastfeeding, and I guarantee "to lose the baby weight" will be in the top 10. At the same time, ask any seasoned breastfeeding mom if they have managed to lose weight while breastfeeding, and I guarantee you'll hear things like

or

or

or

What's the deal? Is it just a myth, that breastfeeding helps us shed the pregnancy pounds? Have we been tricked into thinking Junior will simply suck the calories out of us? Doesn't breastfeeding burns calories? And why can't so many of us lose those last 10 pounds? Is dieting possible while breastfeeding?

Does Breastfeeding Burn Calories?

Breastfeeding does burn calories. How many depends on a few things: Baby's age, how often baby nurses, growth spurts, whether baby nurses exclusively or receives supplemental formula/donor milk, whether baby is on solid foods, and ultimately, how much milk mom produces and how many calories are in each ounce of her milk.

On average, there are 20 calories in each ounce of mature breast milk, but this is just an average and the numbers vary from mom to mom (mostly depending on the fat content of her milk), day to day, hour to hour and even throughout a feeding.

If we take that average of 20 calories per ounce of milk and multiply it by 25 ounces (the average daily milk consumption of an exclusively breast fed 2 to 4 month old baby), we are looking at 500 calories 'burnt' (as in, leaving mom's body) by breastfeeding. You can add a little bit more to that because the body uses up energy ('calories') to make breast milk, too. So, in total, we burn around 550 to 670 calories breastfeeding (about as much as you'd burn during a 45 Minute run!). Most health organizations recommend moms should eat an extra 500 calories while breastfeeding, or 300 calories or so if breast milk is not the only source of nutrition for baby.

So, many moms DO lose weight while breastfeeding because it does burn a lot of calories - but not all do! The question is: Why???

Reason 1: Your Body Is Protecting Milk Supply

One of the biggest - and least talked-about - reasons postpartum weight loss can stall is simply that your body is programmed to safeguard breast milk production.

During lactation, hormones such as prolactin and oxytocin take center stage. Prolactin encourages milk production, but it also signals your body to hold on to a small reserve of fat as insurance for your baby’s next feeding. This isn’t a flaw in your plan or willpower - it’s an ancient survival mechanism that helps keep your milk supply steady, even if food intake fluctuates.

Research shows that many women naturally maintain an extra 5 to 10 pounds of fat until they begin to wean. These stores provide calories and essential fatty acids for breast milk and help buffer short-term energy gaps (like when you miss a meal or your baby cluster-feeds).

What You Can Do:

• Focus on nourishment, not restriction. Aim for a balanced plate - lean protein, high-fiber carbs, and healthy fats - rather than aggressive calorie cuts.

• Eat enough to match your output. Most breastfeeding moms need ~400–500 extra calories a day. Too big a deficit (especially in the first 3 months postpartum) can slow metabolism and decrease milk supply.

• Be patient with the timeline. Sustainable weight loss while nursing often picks up after the first 3 to 6 months, once hormones gradually shift.

  
  

Reason 2: You’re Under-eating - or Cutting Carbs Too Low

When you’re eager to drop the baby weight, it’s tempting to slash calories or skip carbs. But for breastfeeding moms, too little fuel can backfire in two big ways:

1. Milk supply may dip. Your body prioritizes milk production, so if it senses a calorie shortage, it will slow fat loss before it risks reducing milk output.

2. Metabolism slows. Consistently eating below your energy needs lowers thyroid hormones and can decrease the number of calories you burn at rest.

Carbohydrates play a key role here. Whole-food carbs - think oats, quinoa, fruit, sweet potatoes - provide the glucose your body needs to make lactose, the primary sugar in breast milk. Cutting carbs too aggressively can leave you tired, irritable, and craving quick sugar fixes that spike insulin and hinder fat burning.

What You Can Do

• Aim for a gentle deficit. Most nursing moms do best with a daily calorie intake only 250 to 300 calories below maintenance, which still supports steady milk supply.

• Choose complex carbs. Include at least one high-fiber carb at each meal to stabilize blood sugar and keep energy levels even.

• Don’t skip meals. Consistent eating helps regulate insulin and appetite hormones.

Reason 3: You are Chronically Stressed

Okay, is there a mom in the world who is not stressed at least at some point during the day?

It's unrealistic to think we can actually live stressless lives once we reach motherhood level. Gone are the days we can take showers or use the bathroom in privacy, put our feet up at the end of a work day to enjoy a movie, feast on a candle light dinner with our partner or, god forbid, sleep in on the weekend. Let's face it: Life got a whole lot more stressful with kids.

And I know you've heard about the conundrum: Stress releases cortisol, and elevated cortisol levels can lead to weight gain, especially around the midsection.

But turns out, we all have (and need!) Cortisol for our immune function, to maintain blood glucose and more. It's not necessarily the cortisol itself which causes weight gain, but having high and prolonged levels of it, which happens when we're chronically (not temporarily) stressed.

If you are having difficulty losing weight, often crave sugary and fatty foods and gain weight especially around your midsection, you may be chronically stressed.

What You Can Do

• Prioritize rest where you can. Trade chores for naps or consider a short, early-evening bedtime so you catch a solid block of sleep before the first night feed.

• Add small stress-relievers. Ten minutes of deep breathing, a stroller walk in fresh air, or even gentle stretching before bed can lower cortisol.

• Move smart. Gentle walks, yoga, or light strength training support recovery and lower stress, while overly intense or long workouts can raise cortisol further.

• Lean on magnesium-rich foods. Dark leafy greens, pumpkin seeds, and cocoa powder naturally support relaxation.

Simplify your nutrition while you focus on rest: The 21-Day Breastfeeding Meal Plan removes the guesswork so you can nourish your body - even on nights when you barely slept.

Reason 4: Blood Sugar Swings & Insulin Resistance

Constant grazing on quick snacks or skipping meals can create roller-coaster blood sugar levels, which in turn keep insulin elevated. Insulin’s job is to shuttle glucose into cells for energy, but when it stays high for too long, your body is more likely to store fat instead of burning it - even if your total calorie intake isn’t excessive.

The postpartum period can also bring a temporary dip in insulin sensitivity. Hormonal changes, interrupted sleep, and high stress (hello, cortisol!) make it harder for your cells to respond efficiently to insulin. That means the same carbohydrate-heavy snack that was fine before pregnancy may now cause a sharper spike and crash, driving cravings and fatigue.

What You Can Do

• Build balanced plates. Pair every carb with protein or healthy fat - think apple slices with nut butter or whole-grain toast with eggs.

• Prioritize protein. Aim for 20 to 30 grams per meal to stabilize blood sugar, support muscle recovery, and keep you fuller longer.

• Eat on a steady rhythm. Three meals plus a couple of planned snacks help prevent the “I’m starving, give me anything” crash.

• Focus on fiber. Vegetables, legumes, berries, and whole grains slow digestion and blunt blood sugar spikes.

Reason 5: Micronutrient Gaps Slow Metabolism

Even if your calorie intake looks perfect on paper, missing key vitamins and minerals can quietly stall weight loss. Pregnancy, birth, and months of breastfeeding naturally draw down your body’s nutrient reserves. This gradual loss of stored nutrients, sometimes referred to as “postpartum nutrient depletion”, reflects the very real need to replenish essential vitamins and minerals after having a baby.

When these stores run low, your thyroid, metabolism, and energy levels can all take a hit.

Common Culprits

• Iron: Low iron can lead to fatigue and a slower metabolic rate.

• Iodine & Selenium: Essential for healthy thyroid hormone production.

• Vitamin D & B-complex: Support mood, hormone balance, and fat metabolism.

  
  

Because breast milk draws from your nutrient stores, your body prioritizes your baby first. That can leave you running on empty and make fat loss harder, even when you’re eating enough calories.

What You Can Do

• Get labs checked. Ask your healthcare provider about testing iron, vitamin D, and thyroid levels if weight loss has stalled.

• Choose nutrient-dense foods. Seafood, leafy greens, eggs, dairy or fortified alternatives, nuts, and seeds pack multiple micronutrients per bite.

• Consider a high-quality supplement. A postpartum multivitamin or individual supplements can help fill gaps (always confirm with your provider)

Bringing It All Together

Breastfeeding is a demanding season. Your body is healing, producing nutrient-rich milk, and coping with sleepless nights - all while hormones, blood sugar, and nutrient stores shift in ways that can make weight loss feel impossible.

The truth is, you’re not doing anything “wrong.” From protective hormones to stress-driven cortisol spikes, from blood-sugar swings to reduced post-pregnancy nutrient stores, these factors are your body’s way of safeguarding you and your baby. Gentle, sustainable weight loss is absolutely possible - but it starts with nourishment, not restriction.

If you’re ready for practical help, my Done-For-You Breastfeeding Meal Plan was created by a Registered Dietitian and Certified Lactation Counselor to:

• Support a healthy milk supply

• Provide balanced, high-protein meals and snacks

• Replenish key postpartum nutrients

• Create a mild calorie deficit for gradual, lasting results

As a thank you for checking out my blog post, use code 5REASONS to get $5 off the Breastfeeding Meal Plan. Check it out below.

About the Author

This article was written by Marina Lane, a Registered Dietitian and Certified Lactation Counselor with a passion for helping moms nourish themselves and their babies. As a mother of two who were both breastfed until age 3, Marina combines professional expertise with personal experience to provide evidence-based advice and support to breastfeeding moms. With her background in nutrition and lactation, she offers practical, science-backed insights to help you navigate your breastfeeding journey with confidence.