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Unchecked climate change could cost hundreds of thousands of lives by 2050, according to a new study examining how rising temperatures will affect physical activity.

A hotter Earth is feared to leave millions of people worldwide too hot to exercise safely by the middle of the century, with knock‑on effects for health, lifespans and pay packets.

The study, led by scientists in Latin America, modelled data from 156 countries between 2000 and 2022 to see how rising temperatures shape our ability to stay active.

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Their finding is stark: every extra month in a year where the average temperature tops 27.8°C is projected to up global physical inactivity by about 1.5 per cent. In low‑ and middle‑income countries, the increase is even steeper at around 1.85 per cent.

By 2050, that shift could translate into 700,000 more premature deaths each year linked to inactivity, alongside annual productivity losses of roughly £2.8billion.

The authors warn that heat alone could undermine a sizeable slice of the World Health Organization’s goal to cut global inactivity by 15% by 2030.

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Physical inactivity is already a global problem, with roughly one in three adults failing to meet weekly exercise targets.

Hotter, stickier days make everyday movement - walking to work, cycling, outdoor sports - harder and riskier, especially for people who work long hours, commute on foot, or don’t have access to air‑conditioned gyms.

Tropical regions and lower‑income communities, where heat is most intense and shade, cooling and safe facilities are scarcer, are projected to be hit hardest.

On hot days, it’s not just that a jog feels grim after a long shift - it can become unsafe. High heat and humidity strain the heart, dehydrate you more quickly, and increase the risk of heat illness.

Governments are being called on to build shade into the streets by funding tree‑lined walking and cycling routes so people can move safely in hot weather, and subsidise access to air‑cooled sports halls and pools for at‑risk groups, including older adults and outdoor workers.

Writing in their study, published in The Lancet Global Health, the researchers, led by Christian García–Witulski, said: 'Heat exposure imposes physiological constraints through elevated cardiovascular strain and heightened perceived exertion, creating substantial barriers to outdoor physical activity.

"Treating physical activity as a climate–sensitive necessity – rather than a discretionary lifestyle choice – will be essential to prevent a heat–driven sedentary transition and its accompanying surge in cardiometabolic diseases and economic losses."