Reference summary — not medical advice or a personal risk estimate.
Excess body weight
Quick answer
Not IARC-classified — this is not a chemical or physical agent IARC rates. Recognized as a cancer risk factor based on sufficient evidence in humans. Lifestyle. Body fat above what is considered healthy for height and frame, sustained over time.
Summary
Carrying excess body fat is associated with at least 13 types of cancer.
Detail
Major cancer-research bodies (WHO, IARC, WCRF/AICR) identify excess body fat as a risk factor for at least 13 cancers, including postmenopausal breast, colon, rectum, endometrium, esophagus (adenocarcinoma), kidney, pancreas, gallbladder, liver, ovary, thyroid, multiple myeloma, gastric cardia and meningioma. The WCRF Cancer Prevention Recommendations include keeping a healthy weight throughout life and being physically active as core measures.
What's not established
This classification is based on sufficient evidence in humans that this factor can cause cancer. It does not establish a safe exposure threshold, your personal risk, or how this factor's risk compares in size to other Group 1 agents — hazard classifications are not ranked by magnitude.
Regional relevance
global
Documented in these products
Presence in a product category doesn't imply the product causes cancer. Click each to see the source and context.
Evidence sources
Every claim on this page traces back to one of these. Click through to read the primary document yourself.
Primary sources
WHO
WHO — Cancer fact sheet
NCI
NCI — Risk Factors: Obesity
Supporting sources
Canadian Cancer Society
Canadian Cancer Society — Reduce your risk
Cancer Research UK
Cancer Research UK — Causes of cancer and reducing your risk
IARC / WHO — European Code Against Cancer
European Code Against Cancer (5th edition) — 14 ways you can help prevent cancer
Cancer Council Australia
Cancer Council Australia — Causes of cancer
WCRF/AICR
WCRF/AICR — Diet, Nutrition, Physical Activity and Cancer: a Global Perspective (Third Expert Report)
WCRF/AICR
WCRF — Cancer Prevention Recommendations
Last reviewed: October 2026
Official reference list
A government list some readers use alongside the primary evidence. Meyron is not affiliated with it. A chemical being listed does not by itself describe a risk from any particular product.
- California Prop 65 list
State of California's list of chemicals known to cause cancer or reproductive harm.