How to Lose Weight While Breastfeeding Without Hurting Your Supply

You’ve probably heard that breastfeeding “melts the baby weight off.” For some people it seems to; for others the scale barely moves until after weaning. Both are normal.

This guide covers what the research actually shows about breastfeeding and weight, how many calories you need, and how to lose weight gradually without putting your milk supply at risk. For the science of where the energy goes, see how many calories breastfeeding burns. For a personal number, try our breastfeeding calorie calculator.

Does breastfeeding make you lose weight?

A little, on average, but less than many people expect.

• A large US study of 2,102 women found that exclusive breastfeeding for at least 3 months led to about 3.2 pounds (1.5 kg) more weight loss at 12 months postpartum than not breastfeeding or breastfeeding for a shorter time. Partial breastfeeding made no significant difference. The authors called it a small effect.
• A Japanese study of more than 64,000 women found that those who fully breastfed had retained less of their weight gain at 6 months than those who did not fully breastfeed: on average 0.2 kg (about half a pound) versus 0.8 kg (under 2 pounds). The difference was bigger in women who were overweight or obese before pregnancy.

Why isn’t the effect bigger? Making milk does use energy, but most people also feel hungrier and eat more. How much weight you gained in pregnancy, how much milk you make and your activity level all matter, as the Academy of Nutrition and Dietetics notes.

How many calories do you need while breastfeeding?

The National Academies’ 2023 Dietary Reference Intakes for Energy set the current US numbers:

Stage	Energy cost of making milk	Covered by your body’s stores	Extra calories from food
0–6 months, exclusive breastfeeding	About 540 a day	About 140 a day	About +400 a day
7–12 months, partial breastfeeding	About 380 a day	None counted	About +380 a day

These extras are added to what you’d need if you weren’t breastfeeding. Interestingly, the 0–6 month figure already assumes gradual weight loss of about 0.64 kg (1.4 pounds) a month, because some of the energy comes from fat stored during pregnancy. In other words, slow weight loss is expected and built into the standard advice.

You may also see the older figures of 330 to 400 extra calories a day, which the CDC still quotes. The newer and older numbers are close.

A safe pace: about 1 pound a week

The Academy of Nutrition and Dietetics gives two clear guardrails:

1. Aim for about 1 pound (0.45 kg) a week, or about 4 pounds (1.8 kg) a month.
2. Don’t eat less than about 1,800 calories a day. Women who eat less than that may make less milk.

Research backs a moderate approach. In a randomized trial published in the New England Journal of Medicine, 40 overweight women who were exclusively breastfeeding cut about 500 calories a day and exercised 45 minutes, 4 days a week, starting at 4 weeks postpartum. Over 10 weeks they lost about 4.8 kg (10.6 pounds), roughly 0.5 kg a week, compared with 0.8 kg in the control group, and their babies grew just as well.

A Cochrane review of 14 trials (12 of them, with 910 women, contributed data) found that diet, or diet plus exercise, helped women lose more weight after childbirth than usual care, while exercise alone did not make a significant difference to weight. The programs did not seem to harm breastfeeding, though the reviewers said more evidence is needed for breastfeeding women specifically.

What this looks like in practice (our calculation)

Our calculator subtracts 500 calories a day from your total needs, roughly 1 pound a week, and never goes below 1,800. Take the calculator’s first worked example: a 30-year-old, 5 ft 5 in, 150 lb, lightly active mother of a baby under 6 months who is fully breastfed. She needs about 1,930 calories a day without breastfeeding, plus 400 for milk, so about 2,330 a day. A weight-loss target of about 1,830 a day stays above the 1,800 floor. Enter your own details in the breastfeeding calorie calculator to see your numbers.

Eating to lose weight and keep your supply

The Academy of Nutrition and Dietetics suggests:

• Three relaxed meals a day, plus snacks between them. Our list of easy breastfeeding snacks has ideas you can eat one-handed.
• Half your plate vegetables and fruit at lunch and dinner.
• Protein at meals: lean meat, poultry, fish, beans, eggs, nuts and seeds.
• Whole grains instead of refined grains, and healthy oils such as olive or canola.
• Three servings of dairy or calcium-fortified alternatives a day.
• 8 to 12 ounces of lower-mercury seafood a week, avoiding shark, swordfish, king mackerel and tilefish. Our guide to foods to avoid while breastfeeding covers fish in more detail.
• Plenty of fluids, choosing water and unsweetened drinks over sugary ones.

Skip crash diets, meal-replacement-only plans and long fasts. They make it hard to stay above 1,800 calories and to get enough iodine, choline and other nutrients the CDC highlights for breastfeeding.

Exercise while breastfeeding

Activity helps you lose weight and keep muscle, and it won’t hurt your milk:

• Moderate exercise doesn’t reduce milk volume. The Academy of Nutrition and Dietetics says moderate activity such as brisk walking is good for you and will not reduce how much milk you make.
• Build up to 150 minutes a week. ACOG recommends at least 150 minutes of moderate aerobic activity a week after having a baby, for example 30 minutes on 5 days, or short 10-minute walks. Add muscle-strengthening on at least 2 days a week.
• Start when you’re ready. ACOG says that after a healthy pregnancy and vaginal birth, it’s usually safe to start a few days after birth or as soon as you feel ready. After a C-section or complications, ask your ob-gyn first.
• Feed or pump first. ACOG suggests feeding your baby or expressing milk before a workout to avoid discomfort from full breasts.

Be kind to yourself

Stress, anxiety and fatigue can decrease milk production, the Academy of Nutrition and Dietetics notes, and sleep loss can make weight loss harder too. If you’re exhausted, our guide on whether breastfeeding makes you tired explains what’s normal. Many people find the last few pounds go only after weaning, and that’s fine.

Signs to ease off

Slow down, eat more and talk to your provider or a lactation consultant if:

• Your baby has fewer wet or dirty diapers, seems unsatisfied after feeds or isn’t gaining weight well
• You feel dizzy, weak or exhausted

If supply drops, our guide on how to increase milk supply explains what helps.

When to talk to a doctor or dietitian

Get personal advice before or while trying to lose weight if:

• You’re losing weight much faster than about 1 pound a week, or losing weight without trying
• You can’t lose weight despite eating less, or your weight is changing along with tiredness or other new symptoms; a thyroid problem such as postpartum thyroiditis is one possible cause
• You have diabetes, a thyroid condition or a history of an eating disorder
• You follow a vegan or other restricted diet and need help covering nutrients such as vitamin B12, iron and iodine
• You’re considering weight-loss medicines or supplements

A registered dietitian can build a meal plan that fits your life, and an IBCLC can check feeding if your supply or your baby’s growth is a concern. For more on eating well, visit our nutrition and health hub.