How many extra calories does breastfeeding need?
Breast milk contains about 65–70 kcal per 100 ml, and a baby who is fully breastfed drinks around 750–800 ml a day — roughly 500 kcal of energy. Part of that comes from the fat your body stored during pregnancy. That is why official guidance from the Institute of Medicine is:
- Exclusive breastfeeding, 0–6 months: about +330 kcal a day above your normal needs (500 kcal for milk minus about 170 kcal from body stores).
- Breastfeeding 7–12 months (baby also eating solids): about +400 kcal a day, because pregnancy fat stores are mostly used up.
- Partial breastfeeding: roughly half of these amounts.
How the breastfeeding calorie calculator works
Your normal needs are estimated with the Mifflin-St Jeor equation (10 × kg + 6.25 × cm − 5 × age − 161) multiplied by your activity level, then the breastfeeding amount is added. If you choose weight loss, 500 kcal is subtracted, but the target never goes below 1,800 kcal.
Example: a 30-year-old mother, 160 cm, 68 kg, lightly active, exclusively breastfeeding: (680 + 1,000 − 150 − 161) × 1.375 ≈ 1,882 kcal + 330 = about 2,212 kcal a day to maintain her weight.
Calories while breastfeeding: low, normal and high
| Daily intake | Level | What to expect |
|---|---|---|
| Under 1,800 kcal | Too low | May reduce milk supply, energy and mood; risk of nutrient gaps |
| Target minus 300–500 kcal (not under 1,800) | Gentle loss | About 0.25–0.5 kg loss a week without affecting supply for most mothers |
| Around your target | Maintain | Stable weight, good energy |
| Well above your target | High | Gradual weight gain |
Benefits of eating well while breastfeeding
- Steady milk supply and more energy for night feeds.
- Healthy, gradual weight loss after pregnancy.
- Better mood and recovery — iron, vitamin D, omega-3 and protein matter after birth.
- Nutrients for your baby: iodine, vitamin D, DHA and B12 in your diet reach your milk.
Health warnings
- Wait until breastfeeding is well established (about 6–8 weeks) before trying to lose weight.
- Avoid crash diets, detox teas and weight-loss pills — some pass into breast milk.
- Limit caffeine to about 200–300 mg a day (see the caffeine calculator) and avoid high-mercury fish.
- Vegan mothers need a B12 supplement; most mothers need vitamin D. Ask your doctor about iodine and iron.
- Speak to a lactation consultant if your baby is not gaining weight or feeding is painful.
- Talk to your doctor before fasting in Ramadan while breastfeeding.
Easy meals for busy new mums
Keep one-handed snacks ready: dates and nuts, boiled eggs, yoghurt, hummus wraps, fruit and oat bars. Batch-cook dal, chicken curry or soups, and keep a water bottle beside your feeding chair. Read our guides to postpartum nutrition and the benefits of breastfeeding, or see our postnatal nutrition service.
Frequently asked questions
How many extra calories do I burn breastfeeding?
Making milk uses about 500 kcal a day when exclusively breastfeeding. Because some of this comes from fat stored in pregnancy, most mothers need about 330 extra kcal a day in the first 6 months and about 400 extra from 7–12 months.
Can I lose weight while breastfeeding?
Yes, gradually. Once breastfeeding is established, eating about 300–500 kcal less than your needs (but not below about 1,800 kcal) usually leads to safe weight loss of up to 0.5 kg a week.
Will eating less reduce my milk supply?
Small reductions usually do not, but very low-calorie diets, skipping meals and dehydration can. Eat regularly and drink to thirst.
How much water should I drink while breastfeeding?
About 2.7 litres of total fluid a day is a good guide (700 ml more than usual). Drinking a glass of water at every feed helps.
Do I need more protein while breastfeeding?
Yes — about 1.1–1.3 g per kg of body weight a day. Include protein at each meal: eggs, dairy, lentils, chicken, fish or tofu.
Sources
- Institute of Medicine. Dietary Reference Intakes for Energy (lactation EER). 2005.
- EFSA. Scientific Opinion on Dietary Reference Values for energy and for water. 2010/2013.
- Academy of Nutrition and Dietetics. Position paper: nutrition and lifestyle for a healthy pregnancy outcome and lactation.