Obesity Linked to Early-Onset Cancer Risk in Young Adults

WEDNESDAY, Nov. 4, 2026 (HealthDay News) — In young adults, obesity is associated with an increased risk for early-onset cancer, according to a study of Korean adults published online Oct. 27 in the Annals of Internal Medicine.

Jae-Seung Yun, M.D., Ph.D., from The Catholic University of Korea in Seoul, and colleagues examined associations between obesity and early-onset cancer risk in young adults in a nationwide population-based cohort study involving 6,313,338 adults aged 20 to 39 years without prior cancer. Based on Asian-specific criteria, body mass index (BMI) was categorized into five groups (underweight to class II obesity).

A total of 151,893 cancer cases occurred during a mean follow-up of 11.2 years. The researchers found that 10-year cumulative incidence varied from 1.84 to 2.24 and 2.62 percent in the normal-weight, class I obesity, and class II obesity groups, respectively, with absolute risk differences of 0.40 and 0.78 percent. Men had a more pronounced relative association, while women had greater absolute risk differences. People with class I obesity based on BMI and abdominal obesity had a higher 10-year cumulative incidence than those without abdominal obesity in combined BMI-waist circumference analyses (2.45 versus 2.13 percent), exceeding that of those with class II obesity without abdominal obesity (2.20 percent). Cumulative incidence was highest for thyroid, endometrial, and ovarian cancer. For breast cancer diagnosed by age 50 years, obesity was not associated with higher risk.

“Integrated approaches addressing weight management alongside smoking cessation and metabolic health may hold particular relevance for young men, among whom the relative associations were most pronounced,” the authors write.

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