CANCER - Reevaluating the fraction of cancer attributable to excess weight: overcoming the hidden impact of prediagnostic weight loss

Sep 21, 2026

Uploaded by Riley

Objective to quantify how much the population attributable fraction (PAF) for excess-weight cancers may be underestimated when cohorts rely on baseline weight, despite prediagnostic weight loss. Methods used UK Biobank participants aged 40–69 without prior cancer to estimate hazard ratios and PAFs for obesity-related cancers over different follow-up periods. Results showed higher PAFs for cancers arising later (e.g., all obesity-related cancers 17.7% vs 7.2% in >4 vs within 4 years). Conclusion indicates a substantially larger excess-weight contribution than short-follow-up cohorts suggest.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages13

Reading Time33 min

AccessFree to download

Abstract

Objective

Methods

Findings

Conclusion

Introduction

Rationale for possible PAF underestimation

Methods

Study population and design

European Journal of Epidemiology (2024) 39:991–1003 [https://doi.org/10.1007/s10654-024-01](https://doi.org/10.1007/s10654-024-01)146-0 CANCER Reevaluating the fraction of cancer attributable to excess weight: overcoming the hidden impact of prediagnostic weight loss Fatemeh Safizadeh1,2 · Marko Mandic1,2 · Michael Hoffmeister1 · Hermann Brenner1,3,4 Received: 10 January 2024 / Accepted: 30 July 2024 / Published online: 18 September 2024 © The Author(s) 2024 Abstract Objective To evaluate the magnitude of the potential underestimation of the proportion of cancer cases attributable to excess weight, known as population attributable fraction (PAF), due to potential bias from prediagnostic weight loss already present at baseline of cohort studies and to overcome it as much as possible. Methods Data from the UK Biobank cohort participants aged 40–69 without prior cancer diagnosis were analyzed. We assessed the magnitude of associations of excess weight with the incidence of obesity-related cancers combined, and separately for gastrointestinal (GI) and other cancers. Using multivariable Cox proportional hazards models, hazard ratios (HR) and their 95% confidence intervals (CI), and PAFs for excess weight at baseline were estimated for various periods of time after weight measurements. Findings Of 458,660 participants, 20,218 individuals developed obesity-related cancers during a median 11.0-year followup, comprising 8,460 GI, and 11,765 non-GI cancers. PAFs were much higher for cancers occurring more than four years after recruitment than for cancers occurring within the initial four years: 17.7% versus 7.2%, 21.4% versus 11.7% for GI, non-GI and all obesity-related cancers combined, respectively. With respect to total cancer (including cancers with no established relationship with excess weight), PAFs were estimated as 5.1% and 8.8% for the 0–4 and 4-14-year periods of follow-up. Conclusion The proportion of cancers attributable to excess weight is likely substantially larger than previously estimated based on cohort studies with short follow-up time or no or only limited exclusion of the early years of follow-up from the analyses. Keywords Body mass index · Overweight · Obesity · Population attributable fraction · Cancer 􀀍 Hermann Brenner h.brenner@dkfz-Heidelberg.de 1 Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Im Neuenheimer Feld 581, D-69120 Heidelberg, Germany 2 Medical Faculty Heidelberg, Heidelberg University, Heidelberg, Germany 3 Division of Preventive Oncology, German Cancer Research Center (DKFZ) and National Center for Tumor Diseases (NCT), Heidelberg, Germany 4 German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany Introduction Overweight and obesity are well established risk factors fora variety of cancers, such as esophageal (adenocarcinoma), colorectal, pancreatic, renal, endometrial, and postmenopausal breast cancer [1, 2] . Based on meta-analyses of studies evaluating associations of excess weight with individual cancers for which evidence of a causal role was classified as sufficient or strong (either convincing or probable) by the International Agency for Research on Cancer (IARC) and the World Cancer Research Fund (WCRF), the total proportion of cancers attributable to excess weight has been estimated to be approximately 4% globally [3, 4] and in the order of 4 to 8% in different Western countries [5–11] . However, this proportion, which is commonly called population attributable fraction (PAF), may have been underestimated because prediagnostic weight loss may have led to underestimation of overweight and obesity related cancer risks in cohort studies, from which these risks have been derived. Cancer patients may suffer from substantial prediagnostic weight loss [12] . This particularly applies to patients with gastrointestinal (GI) cancers, with 75% of their cancerrelated weight loss happeni

FAQs

What does the study aim to correct regarding excess weight and cancer?

It evaluates how much the population attributable fraction (PAF) of cancers due to excess weight may be underestimated because prediagnostic weight loss can bias baseline risk estimates.

How were associations and PAFs estimated in the study?

Using UK Biobank data, hazard ratios from multivariable Cox proportional hazards models were calculated, and PAFs were estimated for excess weight measured at baseline across different follow-up time periods.

What pattern of PAFs was observed over follow-up time?

PAFs were higher for cancers occurring more than four years after recruitment than for cancers diagnosed within the initial four years (e.g., all obesity-related cancers combined 17.7% vs 7.2%).

Sep 21, 2026

Uploaded by Riley