Study analysis · Aging Clinical and Experimental Research · 2024
Being overweight after 80 was linked to a 33% lower relative risk of dying in men — but the study can't say how many fewer deaths that means.
In Swedish adults over 80, being overweight was linked to a lower relative risk of dying over 15 years, but the absolute benefit is unknown and it doesn't prove extra weight is protective.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study followed a group of older people for many years to see if their weight was linked to their risk of dying. It found a link: people who were overweight tended to live longer. But because the researchers didn't assign people to different weights, they can't prove that the extra weight itself caused them to live longer.
What’s the bottom line?
Researchers followed 2,786 older Swedish adults for 15 years to see how body weight related to death.
How strong is this study?
The study is pretty good for this kind of research because it followed many people for a long time and measured height and weight directly. However, many people dropped out, and other things like illness or smoking could explain the link, so we should be careful about trusting the results too strongly.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
56 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=2786)+20/20
- Follow-up+10/10
100 / 100
54 / 100
- P-valuesno p-values reported
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 561 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. This is an observational cohort study without randomization. Although it has a longitudinal design and adjusts for several confounders, it cannot establish cause-effect relationships because of residual confounding, reverse causation, selection bias, and the lack of experimental control.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement was found in the provided text; unable to assess potential conflicts.
The provided text does not include a COI, funding, or author affiliation section. The study is a population-based cohort from the Swedish National Study on Aging and Care (SNAC/GÅS). No industry ties are evident, but absence of disclosure prevents full assessment.
Key takeaways
- 01
In people 80 and older, being overweight was linked to a lower relative risk of dying: men had about 33% lower relative risk (HR 0.67) and women about 21% lower relative risk (HR 0.79) using classic BMI; using knee-height BMI, overweight men had 29% lower relative risk (HR 0.71) and women 23% lower relative risk (HR 0.77).
- 02
Obese men had 40% lower relative risk (HR 0.60) by classic BMI.
- 03
The study did not report absolute risk reductions.
- 04
The study does not give enough numbers to say exactly how many fewer deaths per 1,000 people this means; overall, 1,296 of 2,786 participants died during 15 years (46.5% crude mortality), but subgroup absolute risks were not reported.
- 05
So the size of the absolute benefit is unclear.
Surprising findings
- Overweight and even obese men aged 80+ had lower relative mortality risk than normal-weight peers.It contradicts standard BMI advice that overweight and obesity increase mortality risk.
- Classic BMI overestimated obesity compared with knee-height BMI, and obese men's survival benefit vanished with KH-BMI.It suggests a measurement artifact rather than true obesity protection.
- The protective association persisted after adjusting for height loss via KH-BMI for overweight, but not for obesity.It shows the overweight paradox is robust to height measurement, but the obesity paradox may be partly misclassification.
Practical takeaways
If you're over 80, don't panic about a BMI of 25–30; focus on muscle mass, physical function, and managing conditions rather than weight alone.
Observational study; absolute risk reduction not reported; findings don't apply to younger adults.
medium confidenceClinicians assessing obesity in older adults with height loss could consider knee-height BMI to avoid overestimating obesity.
KH-BMI is not routine; measurement training needed; no absolute risk data.
medium confidenceMaintain physical activity and adequate protein intake to preserve lean mass, which may explain some protective effect.
This is inferred from the discussion, not directly tested in this study.
low confidenceWhy this study matters
The 'overweight paradox' holds in the oldest old
Among 2,786 Swedish adults aged 60–93 followed for 15 years, men aged 80+ who were overweight had a 33% lower relative risk of all-cause death (HR 0.67, 95% CI 0.52–0.87) versus normal/underweight; women had a 21% lower relative risk (HR 0.79, 95% CI 0.65–0.97). The absolute risk reduction was not reported.
It challenges the idea that BMI 25–30 is universally bad, especially for the oldest old.
Obesity's link depends on how you measure it
Obese men aged 80+ had a 40% lower relative risk of death with classic BMI (HR 0.60, 95% CI 0.41–0.89), but this disappeared with knee-height BMI. Researchers say classic BMI likely misclassified some obese men who were actually overweight.
Shows measurement can change conclusions; knee-height accounts for age-related height loss.
Knee-height BMI: a better ruler for aging bodies?
Knee-height-based BMI uses tibia length to predict maximum adult height and is less affected by spinal shrinkage. Classic BMI overestimated obesity prevalence compared with KH-BMI. After using KH-BMI, only overweight men and women aged 80+ still had lower relative mortality risk (men HR 0.71; women HR 0.77).
Many older adults are classified as obese by standard BMI due to height loss; this may alter clinical advice.
What the study cannot tell you
This was observational, with 40% attrition, and non-participants were older (mean 76 vs 72.9 years). There was no cause-specific mortality, the obese subgroup was small, and absolute risk reductions were not reported. Authors note residual confounding is possible.
Prevents overinterpreting; association is not causation.
Findings were age-specific
The lower relative mortality risk was seen in adults aged 80+, not in those aged 60–79. Authors suggest lack of deaths and statistical power in younger groups may explain the null findings.
Age matters; BMI guidelines may need age-specific tailoring.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Researchers followed 2,786 older Swedish adults for 15 years to see how body weight related to death.
Research results
In people 80 and older, being overweight was linked to a lower relative risk of dying: men had about 33% lower relative risk (HR 0.67) and women about 21% lower relative risk (HR 0.79) using classic BMI; using knee-height BMI, overweight men had 29% lower relative risk (HR 0.71) and women 23% lower relative risk (HR 0.77). Obese men had 40% lower relative risk (HR 0.60) by classic BMI. The study did not report absolute risk reductions.
What this means - more context
The study does not give enough numbers to say exactly how many fewer deaths per 1,000 people this means; overall, 1,296 of 2,786 participants died during 15 years (46.5% crude mortality), but subgroup absolute risks were not reported. So the size of the absolute benefit is unclear.
To evaluate age- and sex-specific mortality risk using classic BMI versus knee-height predicted BMI (KH-BMI) for overweight and obesity in a 15-year follow-up of older Swedish adults aged 60–93.
In 2,786 Swedish adults aged 60–93 followed for 15 years, overweight and obesity were associated with lower all-cause mortality relative risk in those aged ≥80. Classic BMI showed lower relative risk for overweight men (HR 0.67), overweight women (HR 0.79), and obese men (HR 0.60). KH-BMI showed lower relative risk only for overweight men (HR 0.71) and overweight women (HR 0.77). Obese adults ≥80 had no increased relative risk. Absolute risk reductions were not reported.
Methods Used
Population-based cohort (Good Aging in Skåne/Swedish National Study on Aging and Care); measured height, weight, and knee height; calculated classic BMI and KH-BMI; mortality from Swedish death registry; Cox regression adjusted for lifestyle factors and comorbidities; 15-year follow-up.
Main Finding
Among adults aged ≥80, overweight was associated with lower all-cause mortality relative risk: men HR 0.67 (classic BMI) and 0.71 (KH-BMI); women HR 0.79 (classic BMI) and 0.77 (KH-BMI). Obese men had lower relative risk (HR 0.60) by classic BMI only. These are relative hazards; the absolute risk reduction was not reported in this study.
Confidence Level
Moderate: large population-based cohort and 15-year follow-up, but observational design, 40% attrition, possible residual confounding, and no cause-specific mortality limit causal inference.
Study Flags
Red Flags
- •40% attrition; non-participants were older
- •Observational design; residual confounding possible
- •No cause-specific mortality; small obese subgroup; absolute risk reduction not reported
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
Overweight and even obese men aged 80+ had lower relative mortality risk than normal-weight peers.
It contradicts standard BMI advice that overweight and obesity increase mortality risk.
Practical Takeaways
If you're over 80, don't panic about a BMI of 25–30; focus on muscle mass, physical function, and managing conditions rather than weight alone.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 561 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Human Cohort Study
Subject
Moderate probability
on the GRADE evidence scale
This study followed a group of older people for many years to see if their weight was linked to their risk of dying. It found a link: people who were overweight tended to live longer. But because the researchers didn't assign people to different weights, they can't prove that the extra weight itself caused them to live longer.
Strengths
- Population-based longitudinal cohort with 15-year follow-up.
- Large sample size of 2,786 older adults.
- Objective measurement of height, weight, and knee height rather than self-report.
Weaknesses
- Observational design cannot establish causality.
- Residual confounding is likely despite adjustments.
- Possible reverse causation: lower mortality in overweight/obese groups may reflect underlying illness or weight loss in the normal/underweight reference group.
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Researchers followed 2,786 older Swedish adults for 15 years to see how body weight related to death.
Research results
In people 80 and older, being overweight was linked to a lower relative risk of dying: men had about 33% lower relative risk (HR 0.67) and women about 21% lower relative risk (HR 0.79) using classic BMI; using knee-height BMI, overweight men had 29% lower relative risk (HR 0.71) and women 23% lower relative risk (HR 0.77). Obese men had 40% lower relative risk (HR 0.60) by classic BMI. The study did not report absolute risk reductions.
What this means - more context
The study does not give enough numbers to say exactly how many fewer deaths per 1,000 people this means; overall, 1,296 of 2,786 participants died during 15 years (46.5% crude mortality), but subgroup absolute risks were not reported. So the size of the absolute benefit is unclear.
To evaluate age- and sex-specific mortality risk using classic BMI versus knee-height predicted BMI (KH-BMI) for overweight and obesity in a 15-year follow-up of older Swedish adults aged 60–93.
In 2,786 Swedish adults aged 60–93 followed for 15 years, overweight and obesity were associated with lower all-cause mortality relative risk in those aged ≥80. Classic BMI showed lower relative risk for overweight men (HR 0.67), overweight women (HR 0.79), and obese men (HR 0.60). KH-BMI showed lower relative risk only for overweight men (HR 0.71) and overweight women (HR 0.77). Obese adults ≥80 had no increased relative risk. Absolute risk reductions were not reported.
Methods Used
Population-based cohort (Good Aging in Skåne/Swedish National Study on Aging and Care); measured height, weight, and knee height; calculated classic BMI and KH-BMI; mortality from Swedish death registry; Cox regression adjusted for lifestyle factors and comorbidities; 15-year follow-up.
Main Finding
Among adults aged ≥80, overweight was associated with lower all-cause mortality relative risk: men HR 0.67 (classic BMI) and 0.71 (KH-BMI); women HR 0.79 (classic BMI) and 0.77 (KH-BMI). Obese men had lower relative risk (HR 0.60) by classic BMI only. These are relative hazards; the absolute risk reduction was not reported in this study.
Confidence Level
Moderate: large population-based cohort and 15-year follow-up, but observational design, 40% attrition, possible residual confounding, and no cause-specific mortality limit causal inference.
Study Flags
Red Flags
- •40% attrition; non-participants were older
- •Observational design; residual confounding possible
- •No cause-specific mortality; small obese subgroup; absolute risk reduction not reported
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
Overweight and even obese men aged 80+ had lower relative mortality risk than normal-weight peers.
It contradicts standard BMI advice that overweight and obesity increase mortality risk.
Practical Takeaways
If you're over 80, don't panic about a BMI of 25–30; focus on muscle mass, physical function, and managing conditions rather than weight alone.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 561 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Human Cohort Study
Subject
Moderate probability
on the GRADE evidence scale
This study followed a group of older people for many years to see if their weight was linked to their risk of dying. It found a link: people who were overweight tended to live longer. But because the researchers didn't assign people to different weights, they can't prove that the extra weight itself caused them to live longer.
Strengths
- Population-based longitudinal cohort with 15-year follow-up.
- Large sample size of 2,786 older adults.
- Objective measurement of height, weight, and knee height rather than self-report.
Weaknesses
- Observational design cannot establish causality.
- Residual confounding is likely despite adjustments.
- Possible reverse causation: lower mortality in overweight/obese groups may reflect underlying illness or weight loss in the normal/underweight reference group.
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study is pretty good for this kind of research because it followed many people for a long time and measured height and weight directly. However, many people dropped out, and other things like illness or smoking could explain the link, so we should be careful about trusting the results too strongly.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
56 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=2786)+20/20
- Follow-up+10/10
100 / 100
54 / 100
- P-valuesno p-values reported
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 561 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. This is an observational cohort study without randomization. Although it has a longitudinal design and adjusts for several confounders, it cannot establish cause-effect relationships because of residual confounding, reverse causation, selection bias, and the lack of experimental control.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement was found in the provided text; unable to assess potential conflicts.
The provided text does not include a COI, funding, or author affiliation section. The study is a population-based cohort from the Swedish National Study on Aging and Care (SNAC/GÅS). No industry ties are evident, but absence of disclosure prevents full assessment.
Standing
The people behind it
The researchers who wrote the study this analysis is built on.
Authored by
4 researchersIf this is your work, this is how we attribute it on Fit Body Science. Nivetha Natarajan Gavriilidou is listed as the lead author.
- Henrik EkströmCorresponding