Accelerated Childhood Fat Gain Predicts Chronic Pain in Teenage Girls, Study Finds

Children whose body fat rises unusually quickly during childhood may be carrying more than extra weight into adolescence, according to a large new study suggesting that accelerating adiposity is an early warning sign for chronic and widespread pain in the teenage years, particularly among girls. The research, drawn from a prospective Portuguese birth cohort followed from birth to age 13, offers some of the strongest longitudinal evidence yet that the relationship between obesity and pain begins far earlier than the adult populations in which it has typically been studied.

The findings carry substantial public health significance. Chronic pain is increasingly recognized as a global burden, with recent analyses of the Global Burden of Diseases study projecting steep rises in chronic pain prevalence through 2035. Meanwhile, child and adolescent overweight and obesity continue to climb worldwide, with forecasts suggesting that a substantial share of children and adolescents will be affected by mid-century. If elevated or rapidly increasing body fat during childhood predisposes young people to persistent, multi-site pain, then the two epidemics may be intertwined from the very start of life, with implications for how clinicians and policymakers approach prevention.

The study drew on Generation XXI, a population-based birth cohort assembled in Porto, Portugal, and re-evaluated at ages 4, 7, 10, and 13. A total of 4,563 participants had the data needed for analysis. Rather than relying on a single snapshot of body weight, the researchers modeled each child’s individual adiposity trajectory across the four follow-up waves, extracting patterns from mixed-effects polynomial trend models. Two complementary adiposity parameters were examined: fat mass percentage, measured through bioelectric impedance, and body mass index z-scores standardized for age and sex.

Pain was assessed at age 13 using the Luebeck Pain Questionnaire, a validated instrument for pediatric pain research. The investigators classified pain in two clinically meaningful ways: chronic pain, defined as pain lasting longer than three months, and multisite pain, defined as pain reported at two or more body sites. Because multisite pain in adolescence is considered an early marker of risk for widespread pain conditions in adulthood, the distinction matters for anyone thinking about long-term trajectories of musculoskeletal health.

The statistical approach was deliberately forward-looking. Instead of simply comparing children who were heavier at any one moment with their peers, the team tested whether the shape of each child’s adiposity curve from ages 4 to 13 predicted pain outcomes at 13. Linear and quadratic terms captured both the overall level and the acceleration of fat gain. Logistic regression models were adjusted for pubertal development, assessed using Tanner staging, and for participation in programmed physical activity, both of which could plausibly confound or modify the adiposity-pain relationship during this developmental window.

The headline result was strikingly sex-specific. Among girls, quadratic fat mass trajectories, characterized by accelerated fat mass gain over childhood, were associated with significantly increased odds of both chronic pain and multisite pain at age 13. The odds ratio for chronic pain was 1.37, with a 95 percent confidence interval of 1.12 to 1.69, and for multisite pain it was 1.27, with a confidence interval of 1.05 to 1.53. In plain terms, girls whose body fat accelerated more steeply than expected across the decade from age 4 were meaningfully more likely to report persistent pain and pain in multiple body sites as they entered adolescence.

Complementary cross-lagged analyses reinforced the temporal direction of the association. These models test whether adiposity at one wave predicts pain at the next, and vice versa, while accounting for the stability of each measure over time. Among girls, the results suggested that adiposity at age 10 was associated with pain reports at age 13, supporting the interpretation that higher adiposity precedes and predicts subsequent pain rather than simply emerging as a consequence of it. This bidirectional framing is important because pain can plausibly drive weight gain through reduced activity and comfort eating, and the cross-lagged design helps disentangle which direction dominates at this age.

Among boys, the picture was far less conclusive. Only suggestive associations emerged, particularly for quadratic body mass index z-score trajectories in relation to chronic pain, with an odds ratio of 1.34 and a confidence interval of 0.96 to 1.86 that crossed the threshold of statistical significance. The authors caution against overinterpreting these patterns, but the sex difference is consistent with a growing body of evidence that puberty reshapes the relationship between adiposity, hormones, and pain. Estrogenic influences on pain processing are well documented, and puberty marks a well-known divergence in which chronic pain becomes substantially more common among girls than boys.

Several biological mechanisms could explain the link. Adipose tissue is not metabolically inert; it is an endocrine organ that secretes inflammatory cytokines and leptin, both of which are implicated in pain sensitization. Excess weight also imposes mechanical loads on joints and muscles, a pathway well established in osteoarthritis research, where weight reduction has been shown to alleviate symptoms in affected adults. In children, high adiposity is associated with reduced physical function and mobility, and prior work from the same cohort has shown that pain sites can persist and migrate between childhood and adolescence. Sleep disturbance, emotional distress, and sedentary behavior may further connect fat gain and pain in a self-reinforcing cycle.

The practical implications are considerable. The results suggest that adiposity trajectories could serve as an early identifier of children at elevated risk of chronic pain, opening a window for intervention years before pain becomes established. Because the association was strongest with fat mass rather than body mass index alone, the study also hints that body composition, not merely weight-for-height, may be the more informative clinical target. Limitations remain: the cohort is from a single European city, pain was self-reported, and observational designs cannot exclude residual confounding. Still, the prospective design, repeated adiposity measurements, and large sample size make this one of the most rigorous demonstrations to date that the obesity-pain connection takes root in childhood, with girls appearing most vulnerable as their bodies and hormonal environments change.

Subject of Research: Association between childhood adiposity trajectories and chronic and multisite pain in adolescence

Article Title: Adiposity trajectory as a predictor of chronic and multisite pain in the transition from childhood to adolescence: A prospective study of a large birth cohort

Article References: Fernandes, F., Pereira, R., Lucas, R., Severo, M., Lopes, C., & Talih, M. (2026). Adiposity trajectory as a predictor of chronic and multisite pain in the transition from childhood to adolescence: A prospective study of a large birth cohort. International Journal of Obesity. https://doi.org/10.1038/s41366-026-02227-8

Image Credits: AI Generated

DOI: 10.1038/s41366-026-02227-8

Keywords: adiposity trajectory, chronic pain, multisite pain, childhood obesity, birth cohort, fat mass percentage, BMI z-score, adolescence, puberty, Generation XXI, longitudinal study, girls