Years of life
- Published in
- Lancet 2009
- People studied
- 894,576
In 57 studies with almost 900,000 adults, a BMI of 40 to 45 went with 8 to 10 fewer years of life, comparable with smoking. At 30 to 35 it was 2 to 4 years.
- Checked against
- PubMed 19299006
- Published in
- Lancet 2009
- Last checked
- 30 October 2026
Key takeaway
This collaboration pooled data from 57 studies with almost 900,000 adults, mostly in western Europe and North America. Death rates were lowest at a BMI of about 22.5 to 25. Above that, each 5 extra BMI points went with about 30% higher death rates. A BMI of 30 to 35 went with 2 to 4 fewer years of life, and 40 to 45 with 8 to 10 fewer, comparable with smoking.
At a glance
- Type of study
- pooled analysis of 57 long-term studies
- People studied
- 894,576
- How long
- 8 years on average, after leaving out the first 5 years of follow-up
- Compared with
- people with a BMI of about 22.5 to 25
- Main result
- Each 5 BMI points above about 25 went with about 30% higher death rates.
- Strength of evidence
- Long-term or observational studies
What this study does not show
An association from observational data, with BMI measured once at the start. A BMI below 22.5 also went with higher death rates, mainly from smoking-related diseases.
Results from studies in groups of people, mostly in diet and movement programmes. They cannot be promised to any one person. This information is educational and does not replace a consultation with a doctor.
More on why
- Genes explain much of the difference in BMILong-term or observational studies · Stunkard et al., NEJM 1990
- Years of lifeLong-term or observational studies · Prospective Studies Collaboration, Lancet 2009
- Heart failure riskLong-term or observational studies · Kenchaiah et al., NEJM 2002
- Fatty liverLong-term or observational studies · Quek et al., Lancet Gastroenterol Hepatol 2023
- The body burns less after weight lossSmall or uncontrolled studies · Leibel et al., NEJM 1995
- Four or more illnesses at onceLong-term or observational studies · Kivimäki et al., Lancet Diabetes Endocrinol 2022
The next step is a conversation, not a decision
A licensed doctor decides whether any treatment is right for you. The answer can also be no treatment.
1You fill in a short form
2We call you within 24 hours
3A paid 20-minute video consultation with a doctor
4The doctor goes through your options and decides what is right for you