We conduct the first cross-country study of plausible associations between COVID-19 mortality and the share of the overweight among nearly 5.5 billion adults around the globe. A statistically significant positive association is observed between COVID-19 mortality and the proportion of the overweight in adult populations spanning 154 countries. This association holds across countries belonging to different income groups and is not sensitive to a population’s median age, proportion of the elderly, and/or proportion of females. The estimated elasticities of COVID-19 mortality, with respect to the proportion of the overweight in adult populations, are consistently higher for sub-samples of countries that belong to a higher income group. While limits of confidence intervals around the point estimates of these elasticities range between 1.5 and 5.4, on an average, every percentage point increment in the proportion of the overweight in adult populations contributes to an additional 3.5 percentage points to COVID-19 mortality for high income countries. With due caution, our findings call for an effective alignment of public policy regulations with public health priorities.