# Young Adults With Obesity Got Cancer More Often Before Midlife

_Evidence Level: Preliminary · Yun JS et al., Annals of internal medicine, DOI 10.7326/ANNALS-25-02612_

*Obesity and Cancer Risk in Young Adults in Korea : A Nationwide Health Screening Cohort Study.*

- **Evidence Level**: Preliminary
- **Why this grade**: Researchers analysed insurance records of over six million young adults across eleven years; the data are observational and smoking was not measured in detail.
- **Facts**: Design: Retrospective cohort study · Duration: 11.2 years · Funding: No funding (the authors state no primary funding source)
- **Publication Types**: Journal Article
- **Journal**: Annals of internal medicine
- **Sample Size**: 6,313,338 young adults in South Korea
- **Authors**: Yun JS, Mun H, Jung JH, Park Y, Kim SY, Kim K, Ko SH, Ahn YB, Kwon HS, Han K, Son JW
- **Graded and published**: 2026-10-27
- **Last edited**: 2026-10-30
- **Topics**: Metabolic Health, Cancer, Mortality
- **DOI**: https://doi.org/10.7326/ANNALS-25-02612
- **Original Source**: https://pubmed.ncbi.nlm.nih.gov/42932883/

## Summary

Young adults in South Korea with obesity were more likely to be diagnosed with cancer in the years that followed. Among people of normal weight, 1.84 percent got a cancer diagnosis within ten years. In the heaviest group, it was 2.62 percent. The absolute gap is small, but it showed up clearly in a very large group.

Researchers analysed national health insurance records from 2009 to 2021. They covered 6,313,338 people aged 20 to 39 with no previous cancer who had attended a national health check. Over 11.2 years on average, the team tracked who developed cancer. Waist size mattered too. People in the milder obesity group who also had a large waist got cancer more often than people in the more severe obesity group without a large waist. Cancers of the thyroid, the lining of the womb and the ovaries were the most frequent. Breast cancer diagnosed by age 50 was not more common with obesity.

The records do not show that body weight causes cancer. Smoking history, for example, was not measured in detail. And only people who came for health checks were included.

## Practical Takeaway

Young adults with obesity, especially with a lot of belly fat, were diagnosed with cancer more often over the following decade.

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_Canonical: https://longevity-cities.com/en/research/young-adults-with-obesity-got-cancer-more-often-before-midlife · Part of Longevity Cities · Updated 2026-10-30_