# Adiposity and risks of gastrointestinal cancers: A 10‐year prospective study of 0.5 million Chinese adults

## TL;DR

A large study in China found that higher body fat is linked to lower risks of esophageal and stomach cancers but higher risk of colorectal cancer.

## Contribution

The study provides new evidence on how different measures of body fat and fat-free mass relate to specific gastrointestinal cancers in Chinese adults.

## Key findings

- General adiposity was inversely associated with esophageal and stomach cancer risks.
- Central adiposity showed mixed associations, being inversely linked to esophageal cancer but positively linked to colorectal cancer.
- Fat-free mass was inversely associated with esophageal cancer but positively associated with colorectal cancer.

## Abstract

Associations of adiposity with risks of oesophageal squamous cell carcinoma (ESCC) and non‐cardia stomach cancer, both prevalent in China, are still inconclusive. While adiposity is an established risk factor for colorectal cancer, the relevance of fat‐free mass and early‐adulthood adiposity remains to be explored. The prospective China Kadoorie Biobank study included 0.5 million adults (aged 30–79 years) from 10 areas in China. Participants' body size and composition were measured at baseline and at resurveys (amongst a subset). After >10 years of follow‐up, 2350, 3345 and 3059 incident cases of oesophageal (EC), stomach (SC) and colorectal (CRC) cancers were recorded, respectively. Cox regression was used to estimate hazard ratios (HRs) for these cancers in relation to different adiposity traits. General and central adiposity were inversely associated with EC (primarily ESCC) risk, with HRs of 0.81 (95% CI 0.77–0.85), 0.76 (0.72–0.81) and 0.87 (0.83–0.92) per SD increase in usual levels of BMI, body fat percentage (BF%) and waist circumference (WC), respectively. Adiposity was also inversely associated with SC risk [HR = 0.79 (0.75–0.83) and 0.88 (0.84–0.92) per SD increase in usual BF% and WC], with heterogeneity by cardia and non‐cardia subsites, and positively associated with CRC [HR = 1.09 (1.03–1.15) and 1.17 (1.12–1.22) per SD higher usual BF% and WC]. Fat‐free mass was inversely associated with EC [HR = 0.93 (0.89–0.98) per SD increase] but positively associated with CRC [1.09 (1.04–1.14)], while BMI at age 25 was positively associated with all three cancers. After mutual adjustment, general adiposity remained inversely associated with EC and SC, while central adiposity remained positively associated with CRC.

What's New

While obesity is an established risk factor for several types of gastrointestinal cancers, its relationships with oesophageal and stomach cancers are unclear. This prospective study of adiposity with oesophageal (primarily squamous cell carcinoma), stomach (primarily non‐cardia) and colorectal cancer risks assessed multiple bioimpedance and anthropometric traits. General adiposity was inversely associated with oesophageal and stomach (overall and non‐cardia) cancer risks; associations with central adiposity were less clear. The authors also provided new evidence for fat‐free mass, with a suggestive inverse association with oesophageal cancer and a positive association with colorectal cancer.