Thinness in adolescence correlated with risk to bone health in adulthood

Scientific literature has shown that adolescence is a critical period during which bone mass formation peaks. However, data concerning the impact of a low body mass index (BMI) before age 18 on bone health in adulthood and the risk of osteoporosis have been "insufficiently documented," wrote Israeli researchers in an article recently published in JAMA Network Open.To fill this gap, they conducted a retrospective cohort study involving 1,083,491 adolescents aged 16-to-19, followed between 1967 and 2022 via the osteoporosis registry of Maccabi Healthcare Services, Israel's second largest health insurance system. This registry includes weight and height measurements during adolescence, supplemented by sociodemographic and medical data. In addition, adult BMI was available for 74% of the subjects, allowing for analysis of their weight trajectories.The data is quite striking. The incidence rate of osteoporosis in adulthood fell from 330.2 per 100,000 person-years among participants who were "extremely thin" in adolescence (i.e., below the third percentile) to only 78.9 among adolescents who were obese (equal to or above the 95th percentile).Hazard ratios (HRs), adjusted for age, socioeconomic status, education level, and cognitive performance, revealed a marked contrast between the sexes. In women, a low BMI was associated with an HR of 1.88 (95% CI: 1.74 to 2.04), while obesity corresponded to a reduced HR of 0.83 (95% CI: 0.77 to 0.89) compared to a normal BMI. In men, a very low BMI is associated with a HR of 1.82 (95% CI 1.64 to 2.01), while obesity is associated with a HR of 1.04 (95% CI 0.93 to 1.16), with no statistically significant protective effect.Trajectory matters more than initial weightEven more telling, "the highest risk was observed among those who remained underweight from adolescence to adulthood," the authors state, suggesting that it is the persistence of low weight rather than initial weight that impacts risk.The researchers conclude that a teenager who is persistently underweight risks paying the price decades later. Noting that a persistently low BMI almost doubles the risk of osteoporosis in adulthood, they emphasize that "weight habits are formed early, and their effects are felt for a long time." Clinically, these findings could encourage physicians to identify very low BMIs as early as adolescence, particularly in girls, and consider targeted management (nutrition, weight-bearing activity, investigation of underlying causes, appropriate blood density monitoring). The emphasis should clearly be on prevention rather than late intervention, the authors note.This article has been translated from its original French and first appeared on our sister site Profession Santé. Reference:Simchoni M, Landau R, Derazne E, et al. Adolescent Body Mass Index, Weight Trajectories to Adulthood, and Osteoporosis Risk. JAMA Netw Open. 2025;8(8):e2525079. doi:10.1001/jamanetworkopen.2025.25079

Thinness in adolescence correlated with risk to bone health in adulthood

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