Adults who kept five low-risk habits — not smoking, staying near a healthy weight, moving regularly, drinking moderately, and eating well — lived an estimated 12 to 14 years longer, on average, than adults who kept none of them. That's the headline finding from a 2018 analysis of more than 123,000 American health professionals followed for up to three decades, and it's the largest, longest-running estimate of its kind.
| Zero healthy habits | All five healthy habits | Estimated gain | |
|---|---|---|---|
| Women, from age 50 | 29.0 more years | 43.1 more years | +14.0 years |
| Men, from age 50 | 25.5 more years | 37.6 more years | +12.2 years |
What did the study actually measure?
Researchers at the Harvard T.H. Chan School of Public Health tracked 78,865 women in the Nurses' Health Study for up to 34 years and 44,354 men in the Health Professionals Follow-up Study for up to 27 years. Everyone was free of cancer, heart disease, and diabetes at the start. Participants reported their habits on repeated surveys every two to four years, so the five-habit score could change over time as people's lives changed, rather than being fixed from one baseline questionnaire.
The team used those decades of data to calculate death rates for people at each level of the five-habit score, then applied a standard life-table method — the same actuarial approach insurers and the Social Security Administration use — to project how many more years a 50-year-old could expect to live at each level. That's why the result is expressed as "more years from age 50," not a single life-expectancy number: it's a projection built from the death rates actually observed in the group with that habit score.
Where does a 14-year gap in life expectancy come from?
It comes from a much larger difference in death rates, worked backward into years. In the same analysis, people with all five habits had roughly 74% lower all-cause mortality than people with none (a hazard ratio of 0.26), 65% lower cancer mortality (0.35), and 82% lower cardiovascular mortality (0.18) across the follow-up period.¹ Those are relative differences between two groups in this cohort over the study's follow-up — not the odds any one person faces, and not proof that the habits alone, rather than something correlated with them, caused the gap.
What counts as a "healthy habit" here?
The study defined five specific, measurable factors — not a vague wellness checklist:
- Never smoking.
- A body mass index between 18.5 and 24.9 — the conventional "normal weight" range.
- At least 30 minutes a day of moderate-to-vigorous physical activity.
- Moderate alcohol intake — up to roughly one drink a day for women, two for men.
- A high-quality diet — in the top 40% of scores on a standard healthy-eating index, built around vegetables, fruit, whole grains, nuts, and fish, and lighter on red and processed meat, sugary drinks, and refined grains.
Does one habit matter more than the others?
The study didn't rank the five habits individually, but it did show the gain was additive — each added habit moved projected life expectancy up further, with the biggest single jump tied to not smoking. That tracks with decades of separate research on smoking and mortality, which consistently finds it the single largest preventable cause of early death. The practical takeaway isn't "pick the best one," though: the dose-response pattern in the data runs across the whole scale, so four habits beat three, and three beat two, regardless of which habits they are.
This also means the projection isn't anchored to childhood habits. The life-expectancy figures above are calculated from age 50 forward, using habit scores adults reported well into mid-life and beyond — the data describe what an adult's habit score was associated with from that point on, not a window that has to close by a certain age.
What the research says
Li and colleagues found that women with all five habits at age 50 had a projected life expectancy of 43.1 more years, compared with 29.0 more years for women with none — a difference of 14.0 years.¹ Men with all five had a projected 37.6 more years, versus 25.5 for men with none — a difference of 12.2 years.¹
Two limits are worth holding onto. First, this is an observational cohort, not a randomized trial: people who adopt five healthy habits may differ from people who don't in ways the study can't fully account for, so the number is a strong association, not ironclad proof that the habits alone caused the gap. Second, both cohorts were U.S. health professionals — mostly nurses and other health-care workers — who are more educated and more health-engaged than the general population on average, which can affect how closely the exact figures generalize elsewhere. The direction of the finding (healthy habits track with meaningfully longer life) is well supported by a wide body of separate research; the precise "12 to 14 years" figure is this study's estimate for its own cohort.
What you can do this week
- Pick the habit you're furthest from, not the easiest one. If you smoke, quitting is the single highest-leverage change on this list — bigger than any other factor alone.
- Build toward 30 minutes of movement most days. Brisk walking counts; it doesn't have to be a gym session.
- If a healthy body weight is the habit working against you, say so to a clinician. Diet and activity are the first line, and when a body mass index of 18.5–24.9 isn't reachable through those alone, Pallas prescribes compounded semaglutide and tirzepatide when a US-licensed clinician decides it's appropriate.
None of this requires hitting all five habits overnight. The study's own data shows the benefit accrues with each one added — there's no threshold you have to clear before it starts counting.
