Body size and composition trends in U.S. adults with a history of cancer: NHANES 1999–2018

Abstract Purpose High fat mass and low muscle mass are associated with increased mortality and risk of second primary cancers in cancer survivors. This longitudinal study examined trends in body size and composition among US adults with a history of cancer from 1999 to 2018. Methods Data from self-reported cancer survivors aged ≥20 years in the Continuous National Health and Nutrition Examination Survey 1999-2006 and 2011-2018 were analyzed. Outcome measurements included body mass index (BMI, n=3,544) waist circumference (WC, n=3,354), and DEXA-derived indices, including fat mass index (FMI, n=1,767), total lean mass (LM, n=1,775), and appendicular skeletal muscle mass index (ASMMI, n=1,741). Multivariate linear regressions were used to analyze across data cycle associations, adjusting for age, sex, and race/ethnicity. Results Across 19 years, average BMI increased from 27.1 kg/m² to 30.0 kg/m² (p<.001) and average WC increased from 96.1 cm to 103.8 cm (p<.001) among all cancer survivors and increased in Hispanic and non-Hispanic White subgroups, but not non-Hispanic Black or other race/ethnicity subgroups. Total LM increased overall between 1999 and 2006, from 46.6 kg to 49.5 kg (p=.002), and increased in the non-Hispanic White subgroup (p=.009). FMI and ASMMI showed no significant overall changes, although FMI levels remained elevated. Conclusion US cancer survivors experienced notable increases in BMI and WC from 1999 to 2018, with LM gains observed in some racial/ethnic groups, particularly from 1999 to 2006. Implications for Cancer Survivors These findings highlight the need for targeted interventions addressing obesity and fat mass to improve long-term health outcomes among cancer survivors.