Losing weight while breastfeeding: a gentle, safe guide

Breastfeeding uses energy

Making milk takes fuel. The US National Institute of Child Health and Human Development (NICHD) says breastfeeding mums who aren't trying to lose weight typically need 450 to 500 extra kcal a day¹. The CDC recommends 330 to 400 extra kcal for well nourished breastfeeding mothers², and the Northern Ireland health site nidirect says around 500, about one or two healthy snacks³.

The numbers differ a little because your needs depend on how much you feed and what you weighed before. But the message is the same: while you're breastfeeding, you need to eat more than you otherwise would.

That also opens the door to gentle weight loss. NICHD notes that if you'd like to lose weight, you can eat the same as you did before pregnancy, so breastfeeding itself creates the deficit¹.

How fast can you lose weight?

The best trial on this dates from 2000. Forty breastfeeding women who were mildly overweight were randomly split into two groups four weeks after giving birth. One group ate 500 kcal a day less and exercised for 45 minutes four days a week. The other carried on as before⁴.

After ten weeks, the diet and exercise group had lost 4.8 kg against 0.8 kg in the other group. The babies grew just as well in both groups⁴.

So half a kilo a week is a sensible ceiling. That means a deficit of about 500 kcal a day compared with what you burn, breastfeeding included⁴. Strict diets and anything promising fast results aren't recommended while you're breastfeeding⁸.

When can you start?

Give yourself time after the birth. Common advice is to wait until breastfeeding is well established, around two months after birth, before actively trying to lose weight⁷. In the 2000 trial, women started at four weeks, but they were closely monitored⁴.

Your body has done an enormous job, and the early weeks are about sleep, healing and getting feeding going. The scales can wait a little. Have a chat with your health visitor about when the time feels right for you.

Protein and fluids

Breast milk contains protein, and your needs go up while you feed. The European Food Safety Authority (EFSA) recommends an extra 19 g of protein a day for the first six months and an extra 13 g after that⁵. That's roughly a pot of skyr or Greek yoghurt or a couple of eggs on top of what you'd normally eat.

You also lose fluid through your milk. EFSA estimates that breastfeeding women need around 700 ml more fluid a day than other women⁶, and nidirect advises drinking extra fluids throughout the day³.

• Keep a glass of water where you usually feed.
• Have protein at every meal: yoghurt, eggs, fish, chicken, beans or lentils.
• Keep easy snacks to hand so a busy day doesn't leave you eating too little.
• Eat a varied diet. Vegetables, fruit and wholegrains give you and your milk the vitamins and minerals you need.

Listen to your body

Broken sleep makes hunger and fullness harder to read, and it's completely normal for some days to go sideways. If you're tired and hungry, eat. If you notice your supply dropping or your baby seems less satisfied, ease off the deficit and talk to your health visitor or GP.

This isn't about getting back to a particular weight quickly. It's about finding a rhythm that fits life with a little one. You might also like our guides on why your weight fluctuates and working out your daily calories.