Colorectal Cancer Cases Rise in Under-50s as Obesity Explains at Most 15%
Updated
Updated · ScienceAlert · Aug 13
Colorectal Cancer Cases Rise in Under-50s as Obesity Explains at Most 15%
3 articles · Updated · ScienceAlert · Aug 13
Summary
Recorded colorectal cancer rates are rising in people under 50 even as overall colorectal cancer incidence falls, leaving scientists without a clear cause for the age-specific increase.
15% is the most obesity can explain in some models, and other suspects such as pesticides or PFAS fit poorly because older people often had equal or greater exposure while their rates are lower or declining.
2019 and 2025 studies found the pattern is not universal: nearly half of countries analyzed had stable or falling young-onset rates, with increases seen in places such as the US and UK but declines in Italy and Lithuania.
Testing and data quality are among the leading alternative explanations, since younger adults may be diagnosed more often and cancer registries have improved, though those factors still do not fully explain why trends differ by age.