How Have Researchers Estimated the Impact of Excess Weight on Mortality? A Systematic Review.
Clinical Snapshot
PICO Framework
| P — Population | Studies estimating attributable mortality to excess weight across four continents |
| I — Intervention | Various methodological approaches for estimating attributable mortality to excess weight |
| C — Comparator | Different methodological frameworks and calculation methods |
| O — Outcomes | Methodological quality and consistency of attributable mortality estimation approaches |
Bottom Line
This systematic review of 23 studies reveals significant methodological heterogeneity in estimating attributable mortality from excess weight. Key findings include inconsistent BMI cut-offs, variable use of population attributable fraction formulas, and predominant reliance on meta-analysis derived relative risks rather than population-specific data. The authors recommend prioritising cause-specific mortality over all-cause mortality, using WHO BMI standards, incorporating lag times, and utilising population-specific relative risks when available. For Australian researchers, this provides a valuable framework for standardising obesity burden estimation methodologies, particularly relevant for national health surveillance and policy development. The review highlights that while methodological limitations shouldn't prevent estimation, they must be transparently acknowledged to improve comparability across studies and jurisdictions.
Key Findings
P Value: Not applicable - no statistical testing
Effect Size: 23 studies across 4 continents identified
Primary Outcome: Methodological variation in attributable mortality estimation approaches
Nnt Or Sensitivity: 13/23 studies (57%) used standard PAF formula; 14/23 (61%) used meta-analysis derived relative risks
Confidence Interval: Not applicable - descriptive review
Clinical Application
High - provides practical methodological framework for implementation Highly relevant for Australian obesity surveillance and burden of disease studies; aligns with AIHW methodological approaches Public health researchers and epidemiologists estimating obesity-related mortality burden
Abstract
OBJECTIVE: The aim of this review is to describe and reflect on the methodology of the studies that estimate the attributable mortality (AM) to excess weight. The purpose was to provide a methodological framework and serve as a starting point to improve the estimation of AM to excess weight. This will lead to more comparable estimates over time and across countries. METHODS: A systematic review was conducted considering MEDLINE (Ovid), Embase and Web of Science databases. Studies that had estimated AM to excess weight published until December 2024 were included. Data extraction was performed in an ad-hoc table based on the STREAMS-P tool, and a descriptive analysis of the methodology employed was performed. RESULTS: The search strategy yielded 2,163 results. Twenty-three studies estimating AM in four continents were included. The majority estimated AM to all-cause mortality (n = 9) and for cardiovascular diseases (n = 9), followed by cancer without specifying which type of cancer (n = 7). Variation was observed in the body mass index (BMI) cut-off points used to define overweight, obesity and excess weight. Thirteen studies applied the population attributable fraction (PAF) formula denoted by PAF = [P (RR-1)] / [1 + P (RR-1)]. Most of the relative risks (RR) derived from meta-analysis (n = 14), and only a minority studies (n = 6) used RR from national studies based on the population for which AM was estimated. CONCLUSION: This review emphasizes methodological constraints on AM estimation to excess weight. Causes of death causally associated with excess weight should be prioritized rather than relying solely on all-cause mortality. The ideal scenario would be to consider lag times; RR derived from the population under study and to use WHO BMI cut-offs and measured data rather than self-reported weight and height. The absence of this data should not prevent AM estimation if limitations are acknowledged. Expanding available estimates worldwide is essential to improve understanding of the mortality burden associated with excess weight.
References
- 1.García, G., Candal-Pedreira, C., Rey-Brandariz, J., Cid, L. de Luis, & Pérez-Ríos, M. (2026). How Have Researchers Estimated the Impact of Excess Weight on Mortality? A Systematic Review. Current Obesity Reports. https://doi.org/10.1093/eurheartj/ehac544.2390
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