Background: The COVID-19 pandemic disrupted all aspects of daily life across the globe, resulting in limitations on physical movement and regular activity. Prior to the pandemic, the US Armed forces was experiencing an upward trend in obesity. This study sought to evaluate the effects of pandemic “lockdown” measures on body mass index (BMI) in US Navy sailors.

Methods: Retrospective cohort study of active-duty sailors from February 1, 2019, to June 30, 2021. Women with a delivery during or in the year prior to the study period and National Guard/Reserve personnel were excluded. BMI measurements before the pandemic (February 1, 2019- January 1, 2020) and during DoD mitigation efforts (September 1, 2020- June 30, 2021) were obtained for the cohort from the MHS Data Repository. Study analyses included descriptive statistics, percent change, and the Stuart-Maxwell test for homogeneity across BMI categories pre- and during the COVID-19 pandemic.

Results: 98,330 active-duty sailors were identified. The obesity rate rose from 25% to 29% during the pandemic, an increase factor of 16.5%. Highest rate changes in obesity were observed in females, ages <20, White, and Junior Enlisted. Stuart-Maxwell test indicated significant differences across all BMI categories, with the largest contribution to the increase in obesity due to 16.7% of those overweight before the pandemic.

Conclusions: A significant increase in obesity was observed amongst sailors during the DoD COVID-19 mitigation efforts, potentially decreasing the readiness of the force. Future special healthy lifestyle intervention programs should be sex-specific and tailored to younger and Junior Enlisted sailors.