How many years does exercise add to your life?
At age 40, the difference between the best and worst answer here is about 3.3 years of life expectancy — 3.4 for men and 3.1 for women. That is the gap between “300+ min a week” and “basically none”, holding everything else constant.
Exercise has the most misunderstood dose-response curve in health. Almost all of the mortality benefit arrives early: the distance between doing nothing and doing a little is far larger than the distance between doing a lot and doing more. If you are starting from zero, you are standing on the steepest part of the curve.
What each answer costs, at 40
| Answer | Hazard ratio | Years vs. best |
|---|---|---|
| 300+ min a week | 0.91 | best |
| 150–300 min a week | 0.95 | −0.4 |
| 75–150 min a week | 1.02 | −1.2 |
| Under 75 min a week | 1.12 | −2.1 |
| Basically none(desk to couch) | 1.26 | −3.3 |
Computed from the SSA 2023 period life table with this factor’s hazard ratio applied and every other factor held neutral. Source: Arem et al., JAMA Internal Medicine 2015.
Does it matter less as you get older?
Yes, and by a lot. A hazard ratio applies to the years you have left, so the same answer costs less in absolute terms the later you are asked it. That is an argument for changing it early, not for concluding it no longer matters.
| If you are now | Men | Women |
|---|---|---|
| 30 years old | 3.7 yrs | 3.3 yrs |
| 40 years old | 3.4 yrs | 3.1 yrs |
| 50 years old | 3.1 yrs | 2.9 yrs |
| 60 years old | 2.7 yrs | 2.6 yrs |
| 70 years old | 2.2 yrs | 2.2 yrs |
What the evidence actually shows
Arem and colleagues pooled six studies covering 661,000 adults and found that people meeting the recommended 150 minutes a week of moderate activity had about 31% lower mortality than the inactive. Getting there from nothing captured the majority of that. Beyond three to five times the recommended amount the curve flattens entirely — there was no additional benefit, and no harm either.
What to do about it
The steepest part of the curve is the first 75 minutes a week. Going from nothing to a brisk 20-minute walk most days buys back more than doubling an already-good routine.
Where this number is weak
Observational activity studies suffer from reverse causation: people who are already ill move less, which makes inactivity look more lethal than it is. Good analyses exclude deaths in the first few years to reduce this, and the effect survives, but the true figure is probably somewhat smaller than the raw comparison suggests.
More generally: these are observational cohorts, which show association rather than proof of cause. The full methodology sets out every simplification the model makes.
What is it costing you?
The calculator weighs this against your other nine factors and ranks them.
Then make it count. The Extension Plan turns your result into a 12-week plan, starting with the habit worth the most years to you · $9. See what is in it →