As this paper reported yesterday, 31.3 percent of adults worldwide fail to meet the WHO's recommended 150 minutes of weekly moderate physical activity -- a figure that has barely moved in twenty years despite two decades of public health campaigns, fitness apps, and government guidelines. [1] The Nature study that documented this stagnation found 80 percent of countries made no meaningful improvement.

The Lancet Global Health has now added a dimension that transforms the story from failure to forecast. A study published in March projected that rising global temperatures will push an additional 250 million adults below the activity threshold by 2050, producing up to 520,000 additional premature deaths per year. [2] The mechanism is simple: when ambient temperatures exceed 35 degrees Celsius, outdoor exercise becomes dangerous, and people stop going outside. [3] This is already observable across the Gulf states, South Asia, and sub-Saharan Africa, where activity rates are among the world's lowest and falling.

The war compounds the problem indirectly. Countries rationing fuel and shortening office hours -- Bangladesh this week, the Philippines under its energy emergency -- are also reducing access to air-conditioned gyms and indoor recreation. [4] The two-decade failure to move the inactivity needle was already a public health crisis. Climate change is converting it from a chronic condition into an accelerating one.

-- NORA WHITFIELD, Chicago