What's In the Bottle?

Scientists found that babies who are not breastfed have a 30% to 40% increased risk of childhood obesity.1 Milk intake and weight gain vary greatly among formula-fed and breastfed babies.  (For more, see my earlier POST.) Formula-fed babies consume 49% more milk at 1 month, 57% more at 3 months, and 71% more at 5 months.2 This significant difference in milk intake is due in part to how milk flows from breast and bottle.  Recent studies have examined these feeding differences in more detail to help answer the question “How is obesity risk affected when the feeding bottle contains mother’s milk?”  

The study mentioned above provides a partial answer.  Caregivers’ behaviors during bottle-feeding—which are independent of what kind of milk is in the bottle—influence babies’ intake.  For example, when bottles contain more than 6 oz. (177 mL), babies consume more milk.  Also, babies whose caregivers encourage them to finish the bottle are heavier than other babies. 

An important part of obesity prevention is the ability to self-regulate what we eat to match our energy needs.  Breastfeeding naturally teaches babies this self-regulation by giving them more control over feedings.  While breastfeeding, baby must actively draw milk from the breast.  He learns to take milk when hungry and stop when full.  This helps baby become attuned to his body’s hunger and satisfaction cues.  During bottle-feeding, baby’s role is more passive.  Fast, consistent flow and regular coaxing to take more milk, even when full, can lead to a habit of overfeeding and poor self-regulation. That's why if your baby will be bottle-fed often, rather than just laying baby back and tilting the bottle up, use the pacing techniques described HERE.

In one study of 1250 U.S. babies, researchers used bottle-emptying as a measure of poor infant self-regulation.3 (An earlier study verified this link.4) It didn’t matter whether expressed milk or formula was in the bottle.  The more often the babies were fed by bottle during their first 6 months, the more likely they were to empty the bottle during their second 6 months.  Only 27% of the babies who were exclusively breastfed during their first 6 months emptied the bottle during their second 6 months.  Of those fed at first by both breast and bottle, 54% later emptied the bottle.  Of those fed at first only by bottle, 68% later emptied it.

Mother’s milk plays a vital role in a healthy beginning.  But as these studies demonstrate, there is more to breastfeeding than the milk.  Even when mother’s milk is in the bottle, regular bottle-feeding can increase a baby’s risk of childhood obesity. One way we can offset this effect is to make bottle-feeding more like breastfeeding using pacing techniques, which hopefully will decrease the risk of overfeeding.


1 Dewey, K.G., Infant feeding and growth.  In G. Goldberg, A. Prentice, P.A. Filtreau, S., & Simondon, K. (Eds.)  Breastfeeding : Early influences on later health (pp. 57-66).  New York, NY: Springer.

2 Kramer, M. S., Guo, T., Platt, R. W., Vanilovich, I., Sevkovskaya, Z., Dzikovich, I., et al. Feeding effects on growth during infancy. Journal of Pediatrics 2004; 145(5): 600-605.

3 Li, R., Fein, S.B., & Grummer-Strawn, L.  Do infant fed from bottles lack self-regulation of milk intake compared with directly breastfed infants?  Pediatrics 2010; 125(6): e1386-e1393.

4 Li, R., Fein, S.B., & Grummer-Strawn, L.M.  Association of breastfeeding intensity and bottle-emptying behaviors at early infancy with infants’ risk for excess weight at late infancy.  Pediatrics 2008; 122 Suppl 2: S77-S84.

Breast Versus Bottle: How Much Milk Should Baby Take?

Q:  Why does my breastfed baby take at most 4 ounces (120 mL) from the bottle when my neighbor’s formula-fed baby takes 7 or 8 ounces (210-240 mL)?  Am I doing something wrong?

A: You are not doing anything wrong.  And in this case, more is not necessarily better.  Formula-fed babies typically consume much more milk at each feeding than breastfed babies, but they are also more likely to grow into overweight children and adults.1,2One large study (16,755 babies in Belarus) compared feeding volumes in formula-fed and breastfed babies and found that the formula-fed babies consumed 49% more milk at 1 month, 57% at 3 months, and 71% at 5 months.3Australian research found that between 1 and 6 months of age breastfed babies consistently take on average around 3 ounces (90mL) at a feeding. (Younger babies with smaller tummies take less milk.) 

Breastfed babies’ milk intake doesn’t increase from months 1 to 6 because their growth rate slows.4As growth slows, breastfed babies continue to get bigger and heavier on about the same daily milk intake, averaging about 25 ounces (750 mL) per 24 hours.

Why do formula-fed babies drink so much more milk?  There are several reasons: 

  • The bottle flows more consistently. During the first 3 to 4 months of life, after swallowing, an inborn reflex automatically triggers suckling.5 Milk flows more consistently from the bottle than the breast (which has a natural ebb and flow due to milk ejections, or let-downs), so babies tend to consume more milk from the bottle at a feeding. Before this reflexive suckling is outgrown, babies fed by bottle are at greater risk of overfeeding.

  • Breastfeeding gives babies more control over milk intake. Not seeing how much milk is in the breast makes a breastfeeding mother less likely to coax her baby to continue after he’s full.3,6As the breastfed baby grows and thrives, his mother learns to trust her baby to take what he needs from both breast and bottle and also solid foods when they are introduced later. One U.K. study found that between 6 and 12 months of age breastfeeding mothers put less pressure on their babies to eat solid foods and were more sensitive to their babies’ cues.7

  • More milk in the bottle means more milk consumed. In the Belarus study mentioned before, babies took more formula at feedings when their mothers offered bottles containing more than 6 ounces (180 mL).3

  • Mother’s milk and formula are metabolized differently. Formula-fed babies use the nutrients in formula less efficiently,8 so they may need more milk to meet their nutritional needs. Formula is also missing hormones, such as leptin and adiponectin, which help babies regulate appetite and energy metabolism.9,10 Even babies’ sleep metabolism is affected, with formula-fed babies burning more calories during sleep than breastfed babies.11

Q:  If my baby takes more milk from the bottle than I can express at one sitting, does that mean my milk production is low?

A:  See the previous answer.  Babies commonly take more milk from the bottle than they do from the breast.  The fast, consistent milk flow of the bottle makes overfeeding more likely.  So if your baby takes more milk from the bottle than you express, by itself this is not an indicator of low milk production.

To reduce the amount of expressed milk needed and to decrease the risk of overfeeding, take steps to slow milk flow during bottle-feeding: 

  • Use the slowest flow nipple/teat the baby will accept.

  • Suggest the feeder try holding the baby in a more upright position with the bottle horizontal to slow flow and help the baby feel full on less milk.

  • Short breaks during bottle-feeding can also help baby “realize” he’s full before he takes more milk than needed.

For details you can share, see my handout, For the Caregiver of a Breastfed Baby HERE.