About half of U.S. adults spend more than 9.5 hours a day sitting, while roughly 1 in 4 report no leisure-time physical activity, CDC data cited in the report show.
That combination raises risks for heart disease, type 2 diabetes, certain cancers and other chronic conditions as muscles weaken, balance declines and blood-sugar control worsens.
The report says prolonged inactivity can become self-reinforcing: less movement leads to weakness, making activity harder and increasing dependence on medical care over time.
Small bouts of movement throughout the day — walking, taking stairs, standing during calls — can still improve health without requiring intense exercise routines.