Breastfeeding and weight loss: what you really need to know

When a mother breastfeeds, she uses energy to produce milk. Indeed, one study estimates that the energy cost of exclusive breastfeeding is approximately 2.62 MJ per day, which is equivalent to around 625 calories per day [1]. Furthermore, it is known that women need approximately 500 extra calories per day to support milk production. These findings support the idea that exclusive breastfeeding can lead to a significant additional energy expenditure, potentially contributing to the loss of a few kilograms.​

Breastfeeding and weight loss are also influenced by metabolism. For many breastfeeding mothers, it speeds up slightly, as your body works continuously to nourish your baby. That said, this varies from person to person. Some mothers lose weight quickly, while others find their weight plateaus for several months.

Breastfeeding does not mean depriving yourself. Quite the opposite! You need essential nutrients to produce rich breast milk without drawing on your vital reserves. 

For example, the omega-3 fatty acid DHA content depends on the mother's nutrition [2]. The levels of vitamins in breast milk depend largely on the mother's dietary intake. This applies in particular to vitamin A, vitamin D, vitamin C and B vitamins. Among the B vitamins, these are the ones that vary the most depending on diet [3]. Breast milk levels of iodine and selenium also vary according to intake [4]. 

This is one of the reasons why it is often recommended to continue taking your pregnancy food supplement after birth. You can also consider a post-partum food supplement better suited to the needs of breastfeeding. If you choose to take a breastfeeding food supplement specific supplement, check the composition as these are generally designed to support lactation rather than nutritional reserves.  

Your body needs around 450 to 500 extra calories per day to support milk production for your baby [5].

During pregnancy and breastfeeding — periods characterised by rapid growth and the maintenance of maternal and foetal structures — an adequate protein intake is crucial for healthy development [6].

It is also important to maintain adequate hydration, to favour a post-partum diet varied diet and not to lose weight too quickly. An overly restrictive diet can lead to a reduction in milk supply and increased fatigue.

Does breastfeeding really help with weight loss? Yes, but not in a systematic or dramatic way. 

It can be a contributing factor to weight loss through increased energy expenditure. However, other factors also come into play: genetics, level of exercise, sleep, nutrition and hormonal status.

One study in particular showed that breastfeeding had an impact on weight loss in breastfeeding mothers 6–7 weeks after birth, but not at one year, compared to mothers who did not breastfeed. However, it was observed that those who breastfed for one year had a lower BMI, less subcutaneous fat and a lower risk of obesity [7].

There are several common misconceptions on this subject. Among the most widespread:

• « Breastfeeding melts away all the pregnancy weight »: This is false. Whilst some women lose weight quickly, others retain a natural fat reserve that is necessary.
• « You can follow a strict diet whilst breastfeeding »: This can put both the mother and child at risk.
• « Metabolism returns to normal as soon as the baby is born »: In reality, hormonal adjustments take several weeks, or even months.

Unfortunately, we find that breastfeeding women tend to have poorer nutritional quality compared to during pregnancy, even though their nutrient needs are for the most part higher. Similarly, the consumption of food supplements decreases markedly after pregnancy [8].

It is essential to eat a balanced diet and to consume sufficient amounts of iron in particular, as well as calcium, omega-3s, and B vitamins. 

Many diets claim to be suitable for breastfeeding: ketogenic, Mediterranean, vegetarian, vegan, and so on. But they are not all equal! The Mediterranean diet is often recommended, as it is rich in fibre, antioxidants, and essential fatty acids, while remaining moderately calorific [9].

Conversely, a diet too low in carbohydrates and poor in nutritional quality will affect nutrient levels in breast milk and even the mother's general wellbeing. The key is to prioritise moderation and nutritional density over restriction.

What are the risks associated with a too-restrictive diet during breastfeeding? 

If you are not eating properly, you are likely to experience the following: fatigue, mommy brain, reduced milk production, micronutrient deficiencies, irritability, postpartum hair loss, hormonal disruption, and so on. Furthermore, as mentioned above, the content of certain compounds in breast milk depends on the mother's dietary intake. If your nutrition is not optimal, your body will draw on its reserves, and the quality of your milk will be affected. 

It is also advisable to try to maintain a relatively stable weight, so as not to mobilise fat reserves, where pollutants typically accumulate [10]. 

Your body needs time and care, not deprivation. 

How can you readjust after pregnancy while combining breastfeeding and weight loss?

It is important to take a gradual approach: resuming exercise, but gently (walking, postnatal yoga), listening to your body's hunger signals, resting as much as possible, and not comparing yourself to others. Patience and consistency are your best allies.

It is also very important to avoid all women's food supplement for weight loss or otherwise, that contains compounds incompatible with breastfeeding.

To help ensure you meet your nutritional needs and those of your baby, here are some foods to include in your meals: 

• Green leafy vegetables (spinach, kale): rich in calcium, iron and folic acid, essential for preventing deficiencies.
• Fresh fruit (citrus fruits, berries, kiwi): provide vitamins (particularly vitamin C), which support the immune system, promote healthy healing and improve iron absorption.
• Proteins (chicken, eggs, oily fish, lentils): support tissue repair, hormonal synthesis and help meet energy needs.
• Oily fish (salmon, sardines, mackerel): rich in omega-3, essential for the development of the baby's brain and vision.
• Healthy fats (avocado, walnuts, chia seeds, olive oil): support the infant's nervous system and provide sustained energy.
• Dairy products or alternatives (milk, yoghurt, fortified plant-based drinks): sources of calcium, iodine and vitamin D for the bone health of both mother and child.
• Wholegrains (oats, brown rice, quinoa): provide fibre, B vitamins and sustained energy throughout the day.

There is, however, a list of foods to avoid whilst breastfeeding. This is, however, far less restrictive than during pregnancy. Particular attention should be paid to large oily fish such as tuna, sea bass or swordfish, which are high in heavy metals. Soy is also worth noting — the ANSES recommends consuming no more than one soy-containing product per day. 

Furthermore, coffee and breastfeeding or even alcohol and breastfeeding are not completely incompatible, provided certain guidelines are followed. Keep caffeine intake as low as possible, and with alcohol, make sure not to consume any before breastfeeding. 

The post-pregnancy period is one of intense transformation. Breastfeeding can strengthen the bond with your baby, but it can also create tensions: a feeling of "sacrificing your body", guilt about physical changes, or frustration at not returning to your pre-pregnancy weight.

It is therefore crucial to adopt a compassionate approach towards yourself. Losing weight should not become an obsession. It is important to set gradual goals, exercise, and so on. Seeking support from professionals (a nutritionist, midwife, or psychologist) and listening to your body are essential keys to navigating this stage with peace of mind [11].

Breastfeeding and weight loss are a subtle duo. It is not simply a matter of returning to a "pre-baby body", but a journey towards a new form of vitality. It is important to respect your needs, by eating well and allowing yourself time. Depriving yourself to lose a few kilos will be counterproductive. Excessive exercise is not the solution either. You will feel tired, irritable, your milk supply will be affected, and this can lead you to weaning baby prematurely. 

Every mother is different, do not put pressure on yourself. Do not forget that the benefits of breastfeeding for you and your baby are very numerous.