# IARC verdict: excess body fat causes 13 cancers

Source: https://onco.cc/key-papers/paper-body-fatness-iarc-nejm-2016/  
OnCo record `paper-body-fatness-iarc-nejm-2016` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

An IARC working group reviewed over 1,000 studies and concluded there is sufficient evidence that absence of excess body fat lowers the risk of 13 cancers, up from 5 in the 2002 evaluation.

## Summary

The International Agency for Research on Cancer convened a working group in 2016 to re-evaluate body fatness and cancer for the IARC Handbooks of Cancer Prevention, reviewing more than 1,000 epidemiological studies, mostly cohort studies, plus mechanistic evidence on insulin, sex hormones and inflammation.

Sufficient evidence of a cancer-preventive effect of avoiding excess body fat was found for cancers of the oesophagus (adenocarcinoma), gastric cardia, colon and rectum, liver, gallbladder, pancreas, breast (postmenopausal), corpus uteri, ovary, kidney (renal cell), meningioma, thyroid and multiple myeloma. Relative risks rose with BMI, ranging from about 1.1 per 5 BMI units for postmenopausal breast cancer to around 7 for endometrial cancer at BMI 40 or above.

The paper reframed obesity as a leading modifiable cancer cause after tobacco.

## Fields

- Kind: Key paper
- Last checked: 2026-09-08
- Journal: New England Journal of Medicine
- Year: 2016
- DOI: 10.1056/NEJMsr1606602
- Authors: Lauby-Secretan B, Scoccianti C, Loomis D, Grosse Y, Bianchini F, Straif K (IARC Handbook Working Group)
- Findings: Thirteen cancers with sufficient evidence, up from five (colon, oesophagus, kidney, breast, endometrium) in 2002; Strongest associations: endometrial cancer (RR about 7.1 for BMI 40 or more) and oesophageal adenocarcinoma (RR 4.8); Colorectal cancer RR 1.3 and postmenopausal breast cancer RR 1.1 for the highest BMI category studied; Evidence in children and young adults suggests early-life body fatness raises adult cancer risk
- What it means: Maintaining a healthy weight is now established cancer prevention for over a dozen cancer types. For clinicians and policymakers, obesity belongs alongside tobacco and alcohol in prevention strategy. Whether intentional weight loss in adulthood reverses risk is still being studied, including in trials of GLP-1 drugs.
- Caveats: Evidence is observational; residual confounding (diet, activity, socioeconomic status) cannot be excluded; BMI is a crude measure of body fat; central adiposity may matter more; Whether losing weight lowers risk is inferred, mainly from bariatric surgery cohorts; Relative risks for several cancers are modest even though population-attributable fractions are large

## Sources

- DOI: https://doi.org/10.1056/NEJMsr1606602
- IARC Handbooks Volume 16: https://publications.iarc.who.int/570

## Connected records

- ideas: [A delivery-science moonshot for prevention we already own](https://onco.cc/ideas/idea-fund-prevention-moonshot/), [A trial of GLP-1 weight-loss drugs with cancer as the primary outcome](https://onco.cc/ideas/idea-prev-glp1-cancer-prevention-rct/)
- cancers: [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Endometrial cancer](https://onco.cc/cancers/endometrial/), [Gastric & gastro-oesophageal junction cancer](https://onco.cc/cancers/gastric/), [Hepatocellular carcinoma](https://onco.cc/cancers/hcc/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Multiple myeloma](https://onco.cc/cancers/multiple-myeloma/), [Oesophageal cancer](https://onco.cc/cancers/esophageal/), [Ovarian cancer](https://onco.cc/cancers/ovarian/), [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/), [Renal cell carcinoma](https://onco.cc/cancers/rcc/), [Thyroid cancer](https://onco.cc/cancers/thyroid/)
- fronts: [Diet, Exercise & Lifestyle](https://onco.cc/fronts/nutrition-lifestyle/), [Prevention & Risk](https://onco.cc/fronts/prevention/)
- institutions: [International Agency for Research on Cancer (IARC / WHO)](https://onco.cc/institutions/iarc/)
- bottlenecks: [Funding follows fashion, not burden](https://onco.cc/bottlenecks/b-funding-allocation/), [Prevention we already have is not deployed](https://onco.cc/bottlenecks/b-prevention-adoption/)
- journals: [New England Journal of Medicine](https://onco.cc/journals/nejm/)
- key papers: [PREDIMED: a Mediterranean diet with extra-virgin olive oil and fewer breast cancers](https://onco.cc/key-papers/paper-predimed-breast-jama-im-2015/)

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