Physical inactivity accounts for approximately what percentage of breast and colon cancer?

• A. 10-15%
• B. 21-25%
• C. 30-40%
• D. 50-60%

Answer: (B)

Regular physical activity helps lower risk for several cancers by influencing hormones, insulin levels, inflammation, and body fat. For breast and colon cancers, epidemiological research estimates that the population attributable fraction due to physical inactivity is in the low 20s, about 21-25% of cases. In other words, roughly one-fifth to a bit over one-quarter of these cancers could be attributed to not meeting activity guidelines, and could potentially be prevented if activity levels were higher. This reflects that cancer outcomes are determined by multiple factors, with inactivity being a meaningful, modifiable contributor but not the sole cause.

The other ranges are too low or too high given the multifactorial nature of cancer; 21-25% is the commonly cited estimate for the share of breast and colon cancers linked to inactivity.