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

A warmer Earth is feared to render millions of people globally too hot to safely exercise by the mid-century, with subsequent effects on health, life expectancy and wages.

The research, spearheaded by scientists in Latin America, used data from 156 countries between 2000 and 2022 to examine how rising temperatures influence our capacity to remain active.

Their conclusion is stark: every additional month in a year where the average temperature exceeds 27.8°C is projected to increase global physical inactivity by approximately 1.5 per cent. In low- and middle-income countries, the rise is even sharper at around 1.85 per cent.

By 2050, that shift could equate to an extra 700,000 premature deaths annually linked to inactivity, alongside yearly productivity losses of roughly £2.8 billion.

The authors caution that heat alone could jeopardise a significant portion of the World Health Organization’s objective to reduce global inactivity by 15% by 2030.

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Physical inactivity is already a worldwide issue, with about one in three adults failing to meet weekly exercise goals.

Hotter, more humid conditions make routine physical activity – walking to work, cycling, outdoor sports – more challenging and dangerous, particularly for those who work extended hours, travel on foot, or lack access to air-conditioned fitness facilities.

Tropical areas and lower-income neighbourhoods, where temperatures are most extreme and access to shade, cooling systems and secure facilities is more limited, are expected to bear the brunt.

During hot spells, it’s not simply that exercise feels unpleasant after a lengthy shift – it can become hazardous. Elevated heat and humidity place additional stress on the heart, accelerate dehydration, and increase the likelihood of heat-related illness.

Authorities are being urged to incorporate shade into urban planning by financing tree-lined walking and cycling paths so residents can exercise safely during hot weather, and subsidise access to air-cooled sports centres and swimming pools for vulnerable groups, including elderly people and those working outdoors.

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.”