Adiposity and cancer at major anatomical sites: umbrella review of the literature.
Level 3 - non-randomized controlled study
Umbrella review of systematic reviews and meta-analyses of observational studies
PubMed 28246088 · doi:10.1136/bmj.j477
What was done
This umbrella review searched PubMed, Embase, and the Cochrane Database of Systematic Reviews to evaluate systematic reviews and meta-analyses examining the association between adiposity indices and cancer incidence or mortality. The primary analysis focused on cohort studies evaluating continuous measures of adiposity. Evidence strength was categorized as strong, highly suggestive, suggestive, or weak based on multiple criteria: statistical significance of the random-effects estimate and the largest study, number of cancer cases, between-study heterogeneity, 95% prediction intervals, small-study effects, excess significance bias, and credibility ceiling sensitivity analyses.
What was found
The authors evaluated 204 meta-analyses covering seven adiposity metrics and 36 primary cancer types or subtypes. Among 95 meta-analyses of cohort studies using continuous scales, only 12 associations (13%) across nine cancers met criteria for strong evidence. Body mass index (BMI) increases were strongly associated with oesophageal adenocarcinoma, colon and rectal cancer in men, biliary tract system and pancreatic cancer, endometrial cancer in premenopausal women, kidney cancer, and multiple myeloma. Risk increases per 5 kg/m2 increase in BMI ranged from 9% for rectal cancer in men (RR 1.09, 95% CI 1.06 to 1.13) to 56% for biliary tract system cancer (RR 1.56, 95% CI 1.34 to 1.81). A 5 kg adult weight gain increased postmenopausal breast cancer risk in non-users of hormone replacement therapy by 11% (RR 1.11, 95% CI 1.09 to 1.13), and each 0.1 increase in waist-to-hip ratio increased endometrial cancer risk by 21% (RR 1.21, 95% CI 1.13 to 1.29). Categorical metrics added strong evidence for five more associations (weight gain with colorectal cancer; BMI with gallbladder, gastric cardia, and ovarian cancers; and multiple myeloma mortality), yielding 11 cancer sites supported by strong evidence overall.
Why it matters
While obesity is widely cited as a general cancer risk factor, applying rigorous epidemiological criteria narrows the robustly supported associations down to 11 specific anatomical sites, aiding risk stratification and targeted public health prevention.
Limits
The underlying data come entirely from observational studies, meaning residual confounding, exposure misclassification, and reverse causation cannot be fully ruled out. The abstract does not report the total number of primary individual participants across the 204 meta-analyses.
Cited by
- supports Obesity is associated with an increased risk for breast cancer, pancreatic cancer, and colon cancer.