Body mass index and cancer survival: a meta-analysis of cohort studies

We aimed to evaluate the association between BMI and OS in patients with cancer by a combination of available evidence.

Articles published from January 1st 2019 to June 1st 2024 were identified from PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), and Wan Fang Library. Cohort studies including adult patients (≥ 18 years), who were confirmed with cancer and followed for 12 months or more, and whose BMI measurements and OS were available, were included. We used both fixed and random-effects models to estimate overall hazard ratios (HRs) for OS. The primary outcome was OS. The exposure was BMI, which was further classified into four groups based on both WHO and Chinese criteria.

The current meta-analysis included 36 studies, involving 123,913 cancer patients (56,951 men and 66,962 women, medium follow-up 41.3 months). Compared with cancer patients with normal weight, the estimated HRs of OS for underweight was 1.43 (95% CI: 1.30, 1.56; I² = 60; p < 0.001), while it was 0.95 (95%CI 0.90, 1.01; I² = 81; p = 0.11) for those with overweight and obesity where overweight and obesity were combined together. Cancer patients with overweight (HRs = 0.92; 95%CI 0.86, 0.99; I² = 75; p = 0.02), but not with obesity, were associated with a better OS.

Underweight was significantly associated with worse OS in cancer patients. If analyzed separately, only overweight but not obesity had a moderately favorable effect on cancer survival.