We found that adequate breastfeeding (≥ 6 breast milk-months) reduces the overall body size and slows BMI growth velocity both during infancy as well as in the childhood period. These effects were similar in offspring of diabetic and non-diabetic pregnancies, and independent of sex, race/ethnicity, current childhood diet and physical activity levels. Our data provide additional evidence that early infant diet represents a critical period for influencing childhood obesity risk. Moreover, our study indicates that the favorable effects of breastfeeding on BMI growth patterns extend throughout the entire childhood period, and are also present in youth at increased risk for obesity due to intrauterine exposure to maternal diabetes.
While height and weight trajectories increase linearly from birth throughout childhood, the normal development of adiposity, assessed by BMI, is characterized by several phases of overall adiposity gains and losses reflected by negative and positive BMI growth velocity (22
). In the ONDP we found positive growth velocity between 12 and 26 months among subjects with low breastfeeding compared to negative velocity in the adequately breastfed. This represents an accelerated growth pattern where children with suboptimal early life nutrition are accumulating adiposity at an age range when it is waning in their adequately breastfed peers. Subsequently, low vs. adequate breastfeeding was associated with higher BMI growth velocity in both the ONDP and ODP starting at 4 years of age indicating this acceleration of BMI growth extends into childhood. Slower growth in infancy and lower percent body fat composition among breastfed compared to formula-fed infants has been reported in a number of studies (23
). Rzehak et al (25
) developed growth trajectories of weight, length and BMI from birth to age 6 in a large population-based birth cohort in Germany to assess the effect of breastfeeding on childhood growth. The authors reported that infants who were fully breastfed for at least 4 months gained less in the first 12 months of life compared to mixed- or formula-fed children. The DARLING Study (26
) found a similar pattern of increased weight-for-length z
scores between 4 and 18 months of age among formula-fed infants compared to those breastfed for 1 year.
To our knowledge, this is the first study that longitudinally assessed the impact of breastfeeding on BMI growth trajectories among offspring who are exposed fetal overnutrition from maternal diabetes in utero
. Some researchers have expressed concern that breast milk of diabetic mothers could have increased glucose or insulin concentrations that would in fact contribute to fetal programming for future obesity, though the macro-nutrient content of breast milk among well-controlled diabetic mothers has not been demonstrated to be different (27
). Plagemann et al (28
) reported that offspring of mothers with type 1 diabetes who consumed the highest tertile of breast milk in the first week of life were more likely to be overweight and have a worse metabolic profile at 2 years of age compared to those who consumed banked milk. However, a follow-up study by Rodekamp et al. (29
) accounted for intake in the 2nd
weeks of life and found that neither dose nor duration of breastfeeding among offspring women with type 1 diabetes was associated with increased risk of overweight or impaired glucose tolerance at 2 years of age. Among Pima Indian youth exposed to maternal type 2 diabetes or GDM in utero, Pettitt et al (30
) reported a reduction in diabetes risk if the offspring were breastfed for at least 2 months compared to those who were formula-fed (30.1 vs. 43.6%). In the Growing up Today Study (GUTS), Mayer-Davis et al (31
) reported a reduced odds ratio (OR) for risk of overweight at 9–14 years of 0.66 (95%CI 0.53–0.82) associated with exclusive breastfeeding versus exclusive formula feeding among all subjects and a OR of 0.62 (95% C.I.: 0.24–1.60) among youth exposed to maternal diabetes in utero
. And recently, in a cross-sectional analysis of youth enrolled in the EPOCH cohort, we found lower adiposity levels and a less centralized body fat distribution pattern among youth exposed to diabetes in utero
who had adequate neonatal breastfeeding levels (≥6 breast milk months) compared to those with low breastfeeding status. The current study adds an important dimension to our understanding of the influence of early infant diet on the growth and development of children who may be programmed for a faster growth trajectory due to in utero
exposure to over-nutrition from a diabetic pregnancy.
The mechanisms responsible for the favorable long-term effects of breastfeeding on infant and childhood growth patterns are likely multiple. Formula and other types of milk feedings (besides human) have growth accelerating properties on infant weight, length, body fatness and growth velocity (32
). The macronutrient composition of breast milk (i.e., proteins, fat, carbohydrate) and bioactive substances not present in formula may have a protective influence on metabolic programming and regulation of body fatness and growth rates. Another group of potential mechanisms relate to breastfeeding behaviors. For example, smaller or slower growing infants may be deliberately weaned while fast-growing infants would more often be placed on supplementation to reduce crying related to their greater hunger demands (33
). In the current study we found shorter birth length (p=0.03) and smaller birth weight (p=0.07) were associated with low levels of breastfeeding among ONDP which suggests that size at birth may influence breastfeeding behaviors. Additional factors related to breastfeeding that may affect the rate of infant growth include parental control of intake patterns as they can visually assess consumption and want to ‘finish the bottle’, thereby overriding an infant’s innate ability to regulate their meal size and interval based on satiety cues.
Our study has several limitations. Our smaller sample of ODP (n=94) may have limited our ability to detect significant differences in the overall growth trajectory or period-specific growth velocity by neonatal breastfeeding. Information on childhood diet and physical activity patters were only collected once during the research visit, so adjustment for current behaviors may not have adequately removed potential confounding for the entire childhood period. Given the epidemiological nature of this study we were not able to adequately explore the mechanisms responsible for these long-term favorable effects. However, our study also has important strengths including a longitudinal study design and analysis using mixed linear methods which allowed us to explore the effect of breastfeeding on the growth trajectory in infancy and childhood as well as period specific growth. Our cohort was diverse in racial and ethnic youth including non-Hispanic white, Hispanic, and African American. Our assessment of exposure to diabetes in utero was based on clinical records from a large Health Maintenance Organization. And finally, our measure of early infant diet was based on a breastfeeding score which incorporated mixed feeding.
In conclusion, this study provides novel evidence that optimal nutrition the early post-natal period is an important strategy to reduce the risk of childhood obesity. Importantly, this strategy appears to be as effective among offspring of diabetic pregnancies, who are at high risk for becoming overweight or obese early in life, as it is in the larger pediatric population. Moreover, these data support the notion that early postnatal life has long-term influences on growth and development.