Is Being Out of Shape More Dangerous Than Smoking?

For mortality risk, yes. Cleveland Clinic's numbers put it above smoking, diabetes, and heart disease combined.

They tracked 122,000 adults through treadmill testing. The people with the lowest cardiorespiratory fitness had five times the risk of death compared to the highly fit group. Five times. That is a bigger gap than any single disease category in the study.

Sit with that for a second. We treat smoking as the obvious villain. Diabetes gets its own awareness month. Low fitness gets a shrug and a New Year's resolution that dies in February.

The reason it does not get treated with the same urgency is that it is slow and invisible. Nobody collapses from deconditioning at 45. It shows up as "I get tired more than I used to" and "stairs are not what they used to be," and you adjust your life around it instead of fixing it.

VO2 work is not optional in a real program. It is the highest-leverage thing you can do for how long and how well you live, according to the actual data, not the vibes. If your training does not have a real aerobic component built in on purpose, that is the gap to close first.

Source: Mandsager K, et al. JAMA Netw Open. 2018. 122,000+ adults, exercise treadmill testing.