To evaluate the hypothesis that Colorado's lower obesity prevalence is due to higher altitude, which additional data would best help isolate altitude as a causal factor?

A single survey of outdoor recreation participation rates in Colorado without collecting data on altitude, socioeconomic status, or diet, assuming that outdoor activity alone fully explains the difference.

Comparing Colorado's obesity prevalence to the world average and concluding altitude is the cause because Colorado is lower than global rates, ignoring within-country variation and confounding variables.

Using national-level media reports about Colorado's fitness culture to assert causality, since journalistic descriptions reliably quantify population-level physical activity patterns.

A comparative analysis of populations at similar altitudes across different states controlling for socioeconomic status, age distribution, physical-activity levels, and diet, ideally using multivariable regression or matched cohorts.