We know that mom’s weight status during pregnancy can influence the risk of obesity and diabetes in her child. We also know that there are many hormones in breast milk, such as leptin, insulin, and others, which may have an impact on baby’s appetite and metabolism (called the ‘lactational programming hypothesis’). While we know that breastfeeding clearly has a long list of health benefits, including a lower risk of obesity and diabetes in the child later in life, we know remarkably little about the role that breast milk hormones play in modulating this risk.


A recent study examined the effect of weight parameters before, during, and after pregnancy on the hormone content of breast milk.

The study, published in the journal Obesity, enrolled women in their second trimester of pregnancy who had a BMI between 18.5-40 at their first prenatal visit, who were intending to breastfeed exclusively for at least 3 months.   They examined breast milk hormone content at 1 and 3 months postpartum.


They looked at three hormones:

  • Leptin is a satiety hormone made by fat cells (meaning that it tells our brains that we are full). Leptin levels are actually higher in people with obesity, and people with obesity are resistant to its effects (in other words, leptin does not signal fullness as well in people with obesity).
  • Insulin is a hormone that controls blood sugar, and is made by the pancreas. It is also a satiety (fullness) hormone. Obesity is also associated with resistance to the effects of insulin.
  • Adiponectin is a hormone made by our fat cells. It is involved in glucose and fat metabolism, and has anti-inflammatory properties. Adiponectin levels are lower in people with obesity.


They found that the higher mom’s prepregnancy body mass index (BMI), the higher the leptin and insulin, and the lower the adiponectin in her breast milk.

When weight gain in pregnancy exceeded the recommended weight gain, leptin levels were higher in breast milk compared to women who did not exceed the recommended weight gain in pregnancy.

Finally, they found that the greater the postpartum weight loss, the lower the leptin levels in breast milk.


These results show that mom’s weight status before, during, and after pregnancy can have an impact on appetite- and metabolism-regulating hormones in her breast milk. While breast milk overall is clearly associated with a lower risk of obesity and diabetes in the child, more research is needed to understand the role that breast milk hormones (and differences in these hormones) may play in baby’s growth and metabolic health.


Dr Sue Pedersen www.drsue.ca © 2019 

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