Rising temperatures due to climate change could drive millions across the globe into physical inactivity by 2050 by limiting their activity outdoors, suggests a modelling study published in The Lancet Global Health journal. In India, numbers are projected to be higher than the global average.Physical inactivity is already a major global health problem, with about one in three adults failing to meet World Health Organisation (WHO) guidelines for weekly exercise. With projections showing lower activity patterns, the risk of cardiovascular disease, Type 2 diabetes, certain cancers and mental health disorders, all of which shorten life expectancy, increases.The new study means there will be hundreds of thousands of premature deaths and billions of dollars in lost productivity.What the study means for IndiaIn India, the projected increase in inactivity is expected to be above the global average. “The broader message is that heat is not only a matter of comfort. It is capable of shifting population behaviour at scale, with important implications for non-communicable disease risk, health systems and the economy,” Dr Christian García-Witulski, a Research Fellow at the Lancet Countdown Latin America and a Professor at the Pontifical Catholic University of Argentina, told The Indian Express.Also Read | On climate change, mind the science-policy gapResearchers found that each additional month with an average temperature above 27.8C would increase physical inactivity by an average of 1.5 percentage points globally, with an even higher increase of 1.85 points in low and middle-income countries.Country-level projections suggest that adult physical inactivity in India could increase by about two percentage points by 2050. “In addition, our country-level mortality projection attributable to physical inactivity in India is 10.62 deaths per 100,000 people. The projected annual economic cost for India is approximately US$401.9 million. At the broader regional level, South Asia shows median mortality rates attributable to physical inactivity of 3.9, 4.7, and 5.1 deaths per 100,000 across the low-, intermediate-, and high-emissions pathways, respectively. Overall, this suggests that India is part of a region where the health burden linked to climate-driven physical inactivity may be substantial,” says Dr García-Witulski.A question of inequalityThe strongest effects of climate change are concentrated in low- and middle-income settings and in warmer parts of the world, where adaptive capacity is often more limited. “This means the burden is likely to be unevenly distributed, with more vulnerable populations facing the greatest risks,” adds Dr García-Witulski.Story continues below this ad“Using data from 156 countries between 2000 and 2022, we found that each additional month with a mean temperature above 27.8°C is associated with a 1.44 percentage-point increase in adult physical inactivity globally and a 1.85 percentage-point increase in low- and middle-income countries. When we project these effects to 2050 under different climate pathways, we estimate that climate change could lead to 0.47 to 0.70 million additional premature deaths per year and international-dollar productivity losses of 2.40 to 3.68 billion annually,” says Dr García-Witulski.Also Read | Walking vs. wiggling: Expert verdict on the best way to beat office stiffnessThe model predicts the biggest increase in inactivity to be hotter regions such as Central America, the Caribbean, Eastern Sub-Saharan Africa, and Equatorial Southeast Asia, where inactivity could rise by more than 4 percentage points per month spent above 27.8°C.However, the authors highlight that these are modelled projections, based on self-reported activity surveys and only account for temperature changes. So, there are uncertainties about real-world impacts.How to set physical activity targets despite climate changeThe authors say their results suggest that solution-oriented models to climate change need to be devised soon. These could include designing cooler cities, providing affordable air-conditioned places to exercise, provisioning for shaded public areas, giving clear advisories on how to stay safe in extreme heat and reducing greenhouse gas emissions.Story continues below this adAlso Read | Broken pavements, lack of safety: A big reason why Indians struggle to stay fitTree canopies, green roofs and facades lower ambient temperatures. Walking and cycling paths that are well-shaded allow for active transit without over-exposure to UV radiation or extreme heat. Lighter-coloured materials for pavements reduce heat absorption (albedo-friendly) and permeable materials help manage water runoff from flooding.Fitness experts suggest a portfolio of activities rather than relying on one. If a heatwave prevents outdoors, have an indoor option ready with body weight exercises, strength training and indoor routines.