Ages three to four may represent a critical window for preventing early puberty linked to excess childhood weight, researchers say.
Children who gain excess weight during childhood may be more likely to enter puberty earlier, say the researchers of a large international cohort study.
And ages three to four years have emerged as a particularly important period for monitoring and intervention, according to the paper, published in JAMA Network Open.
“Secular trends around the timing of puberty have been apparent for at least the past 100 years,” the researchers wrote.
“Although a recent study in a largely Australian cohort suggests that the age of menarche may have stabilised, there is little evidence to support that the age of onset of other pubertal development events has also stabilised.
“Emerging research shows a parallel rise in the prevalence of early puberty onset since the covid-19 pandemic.
“Early initiation of puberty is associated with increased risk of behavioural and emotional problems during adolescence and with noncommunicable diseases in adulthood, including cardiac disease and gynaecologic cancers.
“In this context, greater understanding of the factors influencing pubertal onset is indicated.”
The researchers analysed data from 4459 children enrolled in birth cohorts in Australia and China and found that higher cumulative exposure to excess weight before puberty was associated with both an earlier age of pubertal onset and a greater likelihood of entering puberty sooner.
The findings suggested that not only obesity itself, but also the length of time a child carried excess weight, may influence pubertal timing.
The study included 3354 participants from the Longitudinal Study of Australian Children and 1105 participants from the Tianjin Birth Cohort Study. Researchers tracked body mass index (BMI) measurements from birth through the first decade of life, using repeated assessments to identify growth trajectories and quantify cumulative exposure to adiposity.
Rather than relying on a single BMI measurement, the researchers examined both the severity and duration of overweight and obesity throughout childhood and compared these measures with parent-reported pubertal onset.
Five distinct BMI trajectory groups were identified in the Australian cohort and four in the Chinese cohort.
Children whose BMI remained high or increased steadily throughout childhood were more likely to experience earlier puberty than those with stable BMI patterns.
In girls, the highest-risk growth trajectories were associated with pubertal onset up to 1.5 years earlier than in children with stable BMI patterns.
These children also had a significantly greater risk of entering puberty during the study period. Similar associations were observed among boys in the Australian cohort, although findings were less consistent among boys in the Chinese cohort.
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The researchers also examined cumulative exposure to adiposity, a measure that captures both how much excess weight a child carries and how long they carry it.
Greater cumulative exposure to overweight and obesity was consistently associated with earlier pubertal timing. Children with prolonged exposure to obesity-level BMI measurements experienced the strongest effects, suggesting that sustained excess weight may have a greater influence on pubertal development than short-term weight gain alone.
A notable finding was the identification of ages three to four years as a potential sensitive period.
Analysis of BMI growth rates showed that rapid weight gain during this preschool window had a stronger association with earlier puberty than weight gain occurring at other ages. In girls, increases in BMI around age four were associated with substantially greater risks of early pubertal onset, while similar patterns were observed among boys in the Australian cohort.
The researchers found that cumulative exposure to excess weight during this age range had larger effects on pubertal timing than exposure occurring outside the period.
They said that this may reflect the importance of early childhood growth patterns, noting that children who gain weight rapidly during the preschool years may undergo adiposity rebound at younger ages.
Earlier adiposity rebound has previously been linked to obesity and earlier pubertal development. The findings also align with previous research showing that much of the excess weight carried by children with obesity is accumulated before they start school.
The study adds to growing evidence linking childhood obesity with pubertal timing. Early puberty has been associated with a range of adverse health outcomes, including behavioural and emotional problems during adolescence, as well as increased risks of cardiovascular disease, metabolic disorders and some cancers later in life.
The researchers noted that earlier puberty may extend lifetime exposure to sex hormones, which has been implicated in the development of conditions such as breast cancer.
While the study relied on parent-reported assessments of pubertal development and used BMI as a proxy measure for adiposity, the researchers said the consistency of findings across two populations strengthened the evidence that excess weight before puberty may influence pubertal timing.
In conclusion, the researchers said the findings highlighted the “importance of considering minimising rapid prepubertal weight gain”.
“Specifically, the findings of an apparently sensitive period at three to four years of age suggest that preschool years may be a priority age window for preventive intervention,” they wrote.
“These findings may have implications for health professionals, parents, and caregivers.”
