Can A Breastfed Baby Be Overweight? 9 Facts To Know

by Renee Kam IBCLC
Last updated January 26, 2021 Reading Time: 6 min

Leading health organisations such as Australia’s National Health and Medical Research Council (NHMRC), the American Academy of Pediatrics and the World Health Organization all recommend exclusive breastfeeding for 6 months (or ‘around’ 6 months).

They also recommend that solids be introduced while breastfeeding continues for at least one year.

Therefore, if you’re exclusively breastfeeding your baby, you’re doing what all the world’s leading health organisations recommend.

But imagine this: you take your baby for her regular visit to the child health nurse. She is measured and weighed and, to your astonishment, you’re told that she’s too fat and you’re feeding her too much!

So you throw your hands up in the air and think to yourself, “But how can that be? I’m exclusively breastfeeding her!”

Can a breastfed baby be overweight?
Here are 9 things you need to know about breastfeeding and weight:

1: Exclusive breastfeeding definition

Firstly, it’s important to define what exclusive breastfeeding means.

Exclusive breastfeeding means that a baby only receives breastmilk. No other liquid or solid food is given, not even water.

A baby who is only fed directly from the breast or fed only breastmilk (from a bottle, breast or a combination of these) is said to be exclusively breastfed.

2: Bottle feeding is different from breastfeeding

How a baby feeds from a breast is very different from how she feeds from a bottle.

When a baby sucks at the breast, she is in control of how much she drinks. She can suck in a way in which she swallows (nutritive sucking) or she can suck without swallowing (non-nutritive sucking). She can be at the breast and not suck at all, or she can just detach herself.

Therefore, no matter how many times a baby breastfeeds or for whatever reason, she remains in control of her intake.

On the other hand, when a baby drinks from a bottle (regardless of what is in the bottle) she cannot suck in a non-nutritive way. A firm bottle teat in her mouth provides a strong stimulus for her to suck and when she does, she gets milk whether she needs it or not. The relatively fast and continuous flow of milk from a bottle means she needs to keep sucking — or be flooded with milk.

Unlike feeding at the breast, drinking from a bottle means it’s possible for a baby to drink more than she needs.

3: How a baby is fed influences the risk of obesity

A baby can be fed in numerous ways. She might be:

Exclusively breastfed directly from the breast
Exclusively breastfed directly from the breast and with breastmilk from a bottle
Exclusively breastfed with breastmilk from a bottle
Mixed fed with formula from a bottle, and breastfed directly from the breast
Mixed fed with formula and breastmilk from a bottle
Mixed fed with formula and breastmilk from a bottle and breastfed directly from the breast
Fed directly from the breast using a breastfeeding supplementer. With this method, a baby might receive only breastmilk, or breastmilk and formula

Within all of these different feeding methods, there are variables such as:

What percentage of the time each method is used, and for how long
How the baby is fed (e.g. with a schedule or according to need, paced bottle feeding or not)
These factors can influence health outcomes, including weight gain.

When it comes to research, it’s very difficult to tease out all the different variables.

Nevertheless, what current research tells us is that, on a population level:

There is no evidence suggesting exclusive breastfeeding increases the risk of becoming overweight or obese
Formula feeding is associated with an increased risk of obesity

4: How formula feeding can increase risk of obesity

Formula feeding can increase the risk of obesity because of formula:

Comes with instructions about how much and how often to feed a baby — this might prompt parents to encourage their baby to finish the bottle
Does not contain the hormone leptin, which helps regulate food intake. Therefore a formula-fed baby’s self-regulation might be reduced
Has a higher protein content than breastmilk, which can contribute to more rapid growth
If you are formula feeding, according to need, choosing a formula with a lower protein content and using a paced bottle feeding method can help reduce the obesity risks associated with formula feeding.

5: Formula-fed babies put on weight differently from breastfed babies

In the first few months, formula-fed babies tend to grow more slowly than breastfed babies. After that, formula-fed babies tend to grow more rapidly than breastfed babies.

There are wide variations when it comes to average weekly gains for a breastfed baby. It’s normal for weight gains to vary from week to week.

As a rough guide, the NHMRC recommends the following for weight gain in infancy:

Birth – 3 months: 150-200 grams per week
3 – 6 months: 100-150 grams per week
6 – 12 months: 70-90 grams per week

6: A mother’s diet does not influence the energy content of her breastmilk

A mother’s diet does not have an impact on the energy content of her breastmilk. This is because the energy content of breastmilk is determined by its concentration of fat, lactose and protein. A mother’s diet does not affect the overall content of these macronutrients in her breastmilk.

7: Feeding according to need is appropriate

Regardless of how a baby is fed, feeding her according to need is appropriate. This helps to ensure she gets the right amount of milk she needs.

Feeding according to need is also important for a breastfeeding mother; it helps her milk supply continue to match her baby’s needs.

8: Breastfeeding is not magic

Breastfeeding is not magic. How an individual is fed as a baby is just one of a myriad things that can influence whether the individual becomes overweight or obese. Genetic and lifestyle factors, for example, also play a role.

If an exclusively breastfed baby ends up overweight or obese later in life, it would not be because she was exclusively breastfed.

9: There are factors that can cause rapid weight gain in exclusively breastfed babies

There’s no evidence that a baby who gains weight rapidly on breastmilk has an increased risk of being overweight or obese later in life. However, here are some factors that might contribute to rapid weight gain in an exclusively breastfed baby:

If your family members grew quickly as babies, it could mean your baby might tend to do the same
If you have an oversupply, this can result in more rapid weight gain in your baby. An oversupply is only of concern if it is causing problems for you or your baby
A medical condition or medication. On rare occasions, if a baby has a certain health problems (e.g. kidney or hormonal problems) or has to take a certain medication (e.g. corticosteroids) these factors could contribute to more rapid weight gain

So, if you’re exclusively breastfeeding and your baby is on the chubby side — relax! This is just how she is meant to be.