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Breastfeeding May Delay Puberty Onset

    Four teenage girls walking side by side to illustrate a new longitudinal study that found that children who were breastfed longer tended to start puberty later.

    Written by: Brittany T. Truong, Ph.D. | Issue # 132 | 2026

    • Early puberty is associated with an increased risk of metabolic and cardiovascular conditions, including type 2 diabetes, obesity, hypertension, and even certain cancers.
    • High BMI during childhood often leads to early puberty.
    • A new longitudinal study finds that children who are breastfed longer tend to start puberty later; however, this was not explained by differences in BMI. 

    Some kids can’t wait until they hit puberty. Pimples, voice changes, and growth spurts are a sign of leaving your childhood behind and becoming an adult. 

    But early, or precocious, puberty can be problematic. In many studies, it has been associated with an increased risk of metabolic and cardiovascular conditions, including type 2 diabetes, obesity, hypertension, and even certain cancers [1].

    “It has also been linked to things like higher risks of mental health challenges [and] earlier engagement in risky behaviors,” adds Maria Ramirez-Luzuriaga, a visiting fellow at the Phoenix Epidemiology & Clinical Research Branch at the National Institute of Diabetes and Digestive and Kidney Diseases. 

    In the last 20 years, researchers have noticed a trend in which children are experiencing puberty earlier than in years past [2]; however, the cause is unknown. Genetics and environmental factors likely play a role. In addition, several studies have suggested that overweight and obesity are high risk factors for early puberty [3]. 

    Breastfed infants, particularly when fed directly at the breast instead of a bottle, are leaner than babies fed formula at 12 months of age. Similarly, breastfeeding has been associated with helping reduce the risk of developing obesity in childhood and later in life [4]. 

    To determine if breastfeeding might delay puberty through its effect on weight, Ramirez-Luzuriaga and colleagues conducted a longitudinal, observational study and followed 613 children from 6 cohorts across the United States in the Environmental Influences on Child Health Outcomes (ECHO) Program. Enrollment for the ECHO Program began in the 1980s and is ongoing. The researchers noted whether and how long the children were breastfed. They also tracked height changes over time and used the individuals’ growth spurts as an objective measure of pubertal timing. The researchers used these measurements to predict growth trajectories, including the age at the onset of puberty, how quickly the individual is growing during puberty (peak velocity), and final adult height [5]. 

    The researchers found that females undergo puberty earlier than males by about 1.3 years. Females experienced a peak velocity in growth at 10.5 years compared with 12.8 years in males [5]. 

    About 13.5% of individuals were exclusively breastfed until they were 3 months old, meaning that they did not consume formula or other foods. The researchers noted that exclusively breastfed individuals experienced a later onset of puberty, as demonstrated by a 4-month delay in peak height velocity. Moreover, after adjusting for socioeconomic, maternal, and infant characteristics, the researchers  showed that each additional 3 months of breastfeeding was associated with a later age of puberty onset and peak velocity in growth [5]. 

    “While the effects of breastfeeding on puberty timing are relatively small—just a few months—they still point to how early-life experiences can shape development in subtle but meaningful ways,” says Ramirez-Luzuriaga. 

    The researchers identified modest associations between exclusive breastfeeding and lower BMI at ages 5 and 10. However, their analyses found no evidence that childhood BMI mediates the association between breastfeeding and puberty onset [5]. 

    According to Ramirez-Luzuriaga, this result was somewhat unexpected, especially given that breastfeeding is usually linked to slightly less weight gain in childhood, and higher body weight in childhood is associated with earlier puberty. 

    “There may be other biological pathways at play, which could be important for pediatric endocrinology research and prevention strategies,” she says. 

    The study had several limitations. The ECHO Program lacked data on potentially important confounding variables, such as maternal pubertal timing or whether breastmilk was pumped or fed directly at the breast. Next, BMI is considered an imperfect measure of obesity, particularly in children, because it cannot distinguish between fat and lean muscle mass [6]. Finally, the researchers note that the statistical model used to predict growth trajectories (the Preece–Baines model) has a tendency to underestimate the age of puberty onset [5]. 

    In terms of next steps, Ramirez-Luzuriaga says it would be nice to “better understand how breastfeeding might influence puberty timing beyond its effect on body weight—looking at things like hormones, metabolism, or early-life nutrition.”

    “While the effects of breastfeeding on puberty timing are relatively small,” says Rarmirez-Luzuriaga. “They still point to how early-life experiences can shape development in subtle but meaningful ways.”

    References

    1. Sun Y, Liu H, Mu C, Liu P, Hao C, Xin Y. Early puberty: A review on its role as a risk factor for metabolic and mental disorders. Front Pediatr. 2024;12:1326864.
    2. Bräuner EV, Busch AS, Eckert-Lind C, Koch T, Hickey M, Juul A. Trends in the incidence of central precocious puberty and normal variant puberty among children in denmark, 1998 to 2017. JAMA Network Open. 2020;3(10):e2015665-e.
    3. Aghaee S, Deardorff J, Quesenberry CP, Jr, Greenspan LC, Kushi LH, Kubo A. Associations between childhood obesity and pubertal timing stratified by sex and race/ethnicity. Am J Epidemiol. 2022;191(12):2026-36.
    4. Yan J, Liu L, Zhu Y, Huang G, Wang PP. The association between breastfeeding and childhood obesity: A meta-analysis. BMC Public Health. 2014 Dec 13;14:1267.
    5. Ramirez-Luzuriaga MJ, Sinha M, Hanson RL. Associations between breastfeeding, childhood bmi and pubertal onset: Findings from a prospective cohort study. Am J Clin Nutr. 2026 Mar;123(3):101208.
    6. Vanderwall C, Randall Clark R, Eickhoff J, Carrel AL. Bmi is a poor predictor of adiposity in young overweight and obese children. BMC Pediatr. 2017 Jun 2;17(1):135.