TOS Scientific Position Statement: Breastfeeding and Obesity

In accordance with the World Health Organization (WHO) recommendation of optimal infant feeding practices, and as interpreted in policy documents of the American Academy of Pediatrics, American College of Obstetricians and Gynecologists, Academy of Breastfeeding Medicine, Academy of Nutrition and Dietetics and many other national groups, it is the position of The Obesity Society (TOS) that women should be encouraged and supported to exclusively breastfeed for approximately the first 6 months of an infant’s life with continued breastfeeding through the infant’s first year and beyond as age-appropriate complementary foods are introduced and as mutually desired by the mother and child.

Breastfeeding rates in the U.S. have steadily increased over the past decade but still remain well below targets. The 2016 report of the National Immunization Survey indicated that 21.9% of mothers were exclusively breastfeeding at 6 months postpartum and 29.2% were breastfeeding at 1 year (1). National objectives for Healthy People 2020 call for increasing the rate of exclusive breastfeeding for 6 months to 25% which remains substantially below the 50% goal established by the WHO Global Nutrition Targets for 2025 (2). Breastfeeding rates are associated with sociodemographic characteristics of mothers including race/ethnicity, level of education, and age (1), as well as maternal BMI. In comparison to normal weight women, breastfeeding is 14% less likely to be initiated in overweight women and 46% less likely in women with obesity (3).

The health benefits of breastfeeding for mothers and children not related to obesity are well established. In mothers who breastfeed, immediate health effects include a more rapid recovery from child birth (e.g., reduced postpartum bleeding and involution of the uterus) and protection from postpartum depression (4). Breastfeeding may also provide longer-term benefits for mothers including protection from breast and ovarian cancers (5). For children, the benefits include reduced mortality and morbidity due to infectious, allergic, and gastrointestinal diseases, fewer hospital admissions due to diarrhea and lower respiratory tract infections (4), lower risk for sudden infant death syndrome (6), and improved cognition (4).

Does Breastfeeding Benefit Mothers for Obesity-Related Outcomes?

Exclusive breastfeeding expends approximately 500 kcal/day, which may influence energy balance and promote weight loss (7), although women may compensate with reduced activity or greater energy intake (8). Many but not all studies have found that a longer duration of breastfeeding is associated with less postpartum maternal weight retention, although some suggest that the beneficial association varies by BMI category (9). Women who have breastfed are observed to have lower risks of visceral adiposity, hypertension, hyperlipidemia, diabetes, and subclinical cardiovascular disease, as well as cardiovascular morbidity and mortality (7), perhaps through mechanisms independent of any effect on adiposity (10). Greater intensity of breastfeeding (greater proportion of breastfeeding as compared to formula feeding) has also been associated with lower risk for type 2 diabetes mellitus after a pregnancy complicated by gestational diabetes (11).

Does Breastfeeding Provide Benefit to Children for Obesity-Related Outcomes?

Compared to infants never breastfed, breastfed infants have a 12% to 24% reduction in the future risk of overweight/obesity (12). Because information on duration and intensity of breastfeeding is not always reported, it is unclear if there is an optimal duration and/or intensity of breastfeeding that is necessary to confer a reduced risk in offspring adiposity. Furthermore, differences in overweight/obesity risk in breastfed versus non-breastfed infants are also likely influenced by differences in parental feeding styles (13,14), patterns of feeding self-regulation (15,16), maternal sociodemographic factors such as race/ethnicity and education, and maternal health (e.g., adiposity, inflammation, insulin resistance) that have been seldom reported or controlled for in published studies (17). Breast milk is a dynamic, nonuniform substance, and aside from its nutritional properties, breast milk comprises multiple compounds including growth factors, cytokines, immunoglobulins, metabolic hormones, oligosaccharides, and microbiota. Associations between these nonnutritive compounds in human breast milk (e.g., insulin, leptin, adiponectin, IL-6, TNF-α) and alterations in infant growth (e.g., length, weight, BMI-z and ΔBMI-z, fat and lean mass) have been reported and are the subject of emerging research (18–21).

Limitations

The primary limitation of the body of evidence linking breastfeeding with postpartum maternal and child health outcomes is that observational studies cannot fully account for differences in sociodemographic factors, physiology, and behaviors between women (and infants) who do and do not breastfeed or between those who breastfeed for shorter or longer durations. Although many studies have attempted to statistically adjust for measured maternal characteristics including education and prepregnancy BMI, substantial differences likely remain in not only measured but also typically unmeasured factors that strongly predict weight gain (22). For example, women who have more abdominal obesity before pregnancy or exhibit adverse eating behaviors such as excessive dietary restraint are less likely to breastfeed (23,24). A large cluster randomized intervention to promote longer duration and greater exclusivity of breastfeeding did not show significant or meaningful improvements in offspring or maternal weight, adiposity, or blood pressure at approximately 11 years after birth (25–27). This intervention was conducted among women who all initiated breastfeeding and so cannot provide information about the comparison of breastfeeding with formula feeding.

Are There Specific Considerations for Women with Obesity and Breastfeeding?

Mothers with obesity are less likely to initiate and maintain breastfeeding (3), even after adjusting for psychosocial and demographic factors (28,29). Higher rates of cesarean delivery and difficulty in positioning the infant at the breast may contribute to this risk; however, defects in maternal physiology are also suggested (28,29). Obesity is a strong risk factor for hyperinsulinemia and prediabetes, yet the role of insulin during breastfeeding is still emerging (30). Similarly, obesity-induced inflammation has recently been shown to compromise breastfeeding by promoting premature involution of the mammary cell (31). There is concern among some clinicians that energy restriction may impair breastfeeding performance; however, studies have indicated that weight loss can be safe during breastfeeding. An energy deficit achieved by a combination of calorie restriction and increased physical activity to promote a 1-pound per week weight loss (i.e., approximately 500-kcal/day deficit), beginning after breastfeeding has been established, can safely be pursued without affecting breast milk composition or infant growth (32,33).

Key Gaps

1. Adequately powered randomized controlled trials do not exist comparing no breastfeeding versus partial or exclusive breastfeeding; however, such trials are likely not ethical or feasible.

2. Mechanisms by which maternal obesity, inflammation, and insulin resistance influence breast milk composition as well as breastfeeding initiation and duration warrant investigation in order to develop interventions to improve maternal and childhood health and to support breastfeeding success in women with obesity.

Suggested Recommendations

1. There is insufficient evidence to confirm that interventions to promote breastfeeding will result in meaningful improvements for maternal and childhood obesity risk at a population level. However, breastfeeding is not associated with adverse outcomes for women or children and may confer obesity-related health benefits for individuals who choose to breastfeed.

2. Social and health care support should be provided for women with overweight and obesity who desire to breastfeed their infants. Once breastfeeding is established, women with overweight or obesity can be supported to reduce energy intake and increase energy expenditure with a goal weight loss rate of 1 pound per week until the desired weight is achieved.