Climate-change related temperature increases are making physical exercise more uncomfortable and dangerous, especially for people in lower-and-middle income countries. A new study from The Lancet estimates this could lead to half a million more premature deaths and aboout $2.5 billion dollars a year in lost economic productivity.

In a village in Upper Egypt, a women’s-only gym complex remained empty and idle as temperatures soared past 40℃ last summer. The women were instead mostly home, sheltering from the intense heat and sun. Their doctors had told them to keep active to stave off the many chronic diseases that plague the village. But in this heat, not even leisure walking through the village where I was a guest and volunteer in July 2025 was an option.

Rising temperatures due to climate change could put routine physical activity out of reach for millions of adults by 2050 – resulting in a about 500,000 more premature deaths and $2.5 billion in lost productivity annually, according to a study just published in The Lancet Global Health.

The study builds on evidence linking climate change-related exposures to a host of poor health outcomes, from direct health impacts like heatstrokes and kidney damage, to the spread of infectious diseases and worsening air quality.

Countries in already warm regions like the Middle East, Central America and the Caribbean, Sub-Saharan Africa, and South-East Asia, are likely to experience the brunt of declining physical activity rates, predicts the study, authored by researchers in Argentina, Chile, Colombia and Ecuador.

‘Profoundly inequitable’

“Because these exposures co-occur disproportionately in tropical LMICs,” wrote the authors, “where air-conditioning penetration, shaded public infrastructure, and discretionary leisure time are scarce—the resulting burden is profoundly inequitable.” 

As is, a third of adults worldwide fail to meet the World Health Organization physical activity guidelines. The WHO recommends a minimum of 150 minutes of moderate intensity or 75 minutes of vigorous intensity physical activity on a weekly basis. Declining physical activity rates are linked to cardiovascular diseases, cancer and diabetes, poor mental and brain health, and an estimated 5% of all adult deaths.

“Lives are becoming increasingly sedentary through the use of motorized transport and the increased use of screens for work, education and recreation,” says the WHO.

Heat drastically affects how active people can be, according to the group of Latin American-based researchers. That includes not only leisurely activity, like playing a sport or running, but also occupational physical activity and active transport like walking or cycling.

The researchers analyzed self-reported data from 156 countries between 2000 and 2022 to predict how rising temperatures could affect physical activity in the coming decades.

The implications of fewer opportunities for physical activity due to heat translates to a estimated 470,000-700,000 more premature deaths annually and between $2.40 and $3.68 billion in productivity losses, depending on the scenario of temperature increase. 

Lower- and middle – income countries hardest hit

The burden of reduced exercise falls most heavily on already warmer equatorial regions, where physical activity is projected to decline 4% for each month spent over 27.8℃ (82℉). Globally, that number is 1.4%, while in lower-and-middle income countries (LMICs), the study authors estimated a 1.85% decline. 

Those living in the climate change “hotspots” of Central America, the Caribbean, eastern sub-Saharan Africa, and equatorial southeast Asia are more susceptible to increases in physical inactivity, the authors found.

“Outdoor labourers, street vendors, and subsistence farmers cannot easily shift physical exertion to cooler hours,” wrote Dr Christian García-Witulski of the Pontificia Universidad Católica Argentina, the lead study author. 

Furthermore, women and adolescents in LMICs face additional barriers to exercise, he noted and already have lower rates of exercise. “[They] often lack access to climate-controlled recreational spaces; and public health budgets in these settings are least able to absorb downstream cardiometabolic costs.

In higher-income countries, where adaptation to rising temperatures such as indoor gyms and air conditioning is perhaps more accessible, the authors projected no statistically significant change.

A ‘feedback loop’ between heat and sedentary behavior

The connection between temperature and the decline in physical activity has several pathways, the authors note.

Physiologically, “heat elevates skin blood flow and sweating, increasing cardiovascular strain, dehydration risk, and perceived exertion.” In addition, high vapour pressure and poorer air quality from smog make breathing uncomfortable, pushing people to avoid outdoor movement – perhaps taking the bus or driving instead of walking to work or school – and staying inside air conditioning.

Globally, the share of households with residential AC is projected to grow from 27% to 41% by 2050, according to a 2024 Nature modeling study. This could further exacerbate sedentary behavior, as air conditioned spaces provide cool refuge but do little to encourage being active. 

This “reinforces a feedback loop between heat and physical inactivity,” García-Witulski wrote.

Rise in premature deaths, lost productivity

Because measures of physical activity also include occupational settings – like agriculture, construction, and other outdoor jobs – heat-driven physical inactivity also threatens economic output. 

Higher temperatures are linked to reduced muscular strength, impaired cognition, and poor sleep – all translating into lower on-the-job performance and higher absenteeism, the authors note.

“Outdoor labourers, street vendors, and subsistence farmers cannot easily shift physical exertion to cooler hours,” García-Witulski and colleagues wrote.

This all means that the model estimated between $2.4 and 3.7 billion in economic losses attributable to rising temperatures, depending on the warming scenario; the study looked at three. Along with that are the projected premature deaths linked to inactivity – 470,000 to 700,000 additional deaths globally. 

“Physical inactivity is a silent threat to global health, contributing significantly to the burden of chronic diseases,” said Dr Rüdiger Krech, Director of Health Promotion at WHO during the release of WHO data on the topic last year.

García-Witulski and her colleagues undertook this research as part of the Lancet Countdown project tracking progress on health and climate change in Latin America. And though they found that warming temperatures will intensify sedentary behaviors, the authors noted that their modeling had several limitations.

For one, the study relied on self-reported physical activity from its 5.7 million participants, instead of measurement devices, potentially leading people to over-or-under report their activity levels. They also examined only annual, national physical activity averages – and did not differentiate between the kind of physical activity such as leisure, occupational, or transport.

And lastly, the authors only examined temperature, and not any other metric of climate change such as extreme weather events. 

Regardless, the authors strongly argued for policies that would make cities heat resilient: “Without stronger mitigation, rising temperatures alone could undermine—or even reverse—a substantial share of WHO’s target of cutting global physical inactivity by 15% by 2030,” they wrote.

Interventions such as expanding shade and tree cover, expanding access to cooling centers, and walking and cycling-friendly roads are all part of creating more resilient cities. 

Adding in air conditioning to the women’s gym in the Upper Egyptian village could also encourage more users in peak summer heat. “They still need the exercise,” said the volunteer who runs the facility. 

The study authors echoed this sentiment: “[T]reating 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.”

Sophia Samantaroy spent seven months in Egypt as a research fellow with the non-profit Coptic Orphans in 2025. She also contributes to Health Policy Watch as a reporter covering environmental health, chronic and infectious diseases, and US public health policy.

Image Credits: S. Samantaroy/HPW, WHO, The Lancet, The Lancet Global Health, Mario Spencer/Unsplash, The Lancet.