As climate extremes intensify, researchers warn that both heat waves and cold snaps are pushing people toward fattier diets, raising long-term risks for obesity and chronic disease.
Study: Extreme Temperatures Promote High-Fat Diets. Image Credit: Quality Stock Arts / Shutterstock
*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
In a study posted to the medRxiv* preprint server, researchers investigated the impact of short-term exposure to extreme temperatures on macronutrient intake, specifically the increased likelihood of consuming high-fat diets.
Background
On sweltering or freezing days, we often reach for different foods, but can weather systematically influence what we eat? In China, over 50% of adults are overweight or obese, a figure projected to rise sharply as climate conditions worsen. While previous research has focused on how climate affects crop yields, little is known about its direct influence on personal eating behavior. This is a critical gap, as diet is a key mediator between environmental change and health outcomes. With obesity-related healthcare costs rising globally, understanding this link is urgent. Further research is needed to explore the relationships between climate and diet in diverse settings.
About the study
Researchers used data from the China Health and Nutrition Survey (CHNS), which covered 28,941 individuals across nine provinces between 1991 and 2011. Participants reported their food consumption over a three-day recall period, from which intake of carbohydrates, proteins, and fats was calculated. Meteorological data from the China Meteorological Data Sharing Service were merged to assess temperature exposure using cumulative cooling degree days above 25°C and heating degree days below 5°C.
A fixed-effects regression model was applied, controlling for individual, time, and regional variables. The model also included additional meteorological controls, such as humidity, rainfall, wind, and sunshine. Researchers analyzed the impact of adaptation technologies by incorporating data on household ownership of fans, air conditioners, refrigerators, and heating systems.
Accuracy checks included adjustments for physical activity, occupation, and alternative definitions of temperature thresholds. Subgroup analyses were performed based on age, gender, location, and education. Importantly, the study focused on short-term dietary responses to temperature changes, as food consumption was measured over a three-day window. Hence, the results reflect immediate rather than long-term adaptations. The authors note that their data relies on self-reported dietary recalls, which may introduce measurement errors, and that their findings pertain to short-term dietary changes rather than chronic effects. To estimate long-term trends, researchers projected changes in dietary patterns through the end of the century using temperature projections from the NASA Earth Exchange Global Daily Downscaled Projections under Representative Concentration Pathway 8.5 (RCP8.5), which assumes high greenhouse gas emissions with minimal mitigation efforts.
Study results
Exposure to extreme temperatures has a significant impact on food consumption and nutrient composition. A 1°C increase above 25°C resulted in a 0.27% decline in food consumption and a 0.29% decrease in energy intake. These reductions were driven by decreases in carbohydrate intake by 0.39% and protein intake by 0.59%, while fat intake remained nearly unchanged. In contrast, a 1°C drop below 5°C increased consumption across all macronutrients, with fat intake rising by 0.34%, a greater increase than for carbohydrates or protein.
Both heat and cold exposure increased the proportion of energy derived from fat, thereby increasing the likelihood of consuming a high-fat diet. A three-day heatwave increased this probability by 6.96%, while a cold spell resulted in a 2.69% decrease. The stability of fat consumption during heat and the larger increase during cold led to unhealthy dietary shifts, particularly toward fat-dense items like milk, eggs, nuts, and oil.
Adaptation strategies showed varying effectiveness. Fans and air conditioners helped reduce the heat's adverse impact by boosting carbohydrate and protein intake. Air conditioners reduced fat intake by 0.52%. Heating systems reduced food and nutrient intake during cold exposure, with the largest decline seen in fat intake. Refrigerators showed a limited impact on fat consumption, indicating that these dietary changes are more likely driven by physiological responses rather than food accessibility. The study highlights that temperature-induced dietary changes are mainly due to physiological appetite regulation—such as changes in hunger or satiety—rather than limitations in food availability.
Disparities emerged among different population groups. Rural and less-educated individuals were more vulnerable to temperature-related dietary shifts, likely due to limited access to cooling and heating technologies, as well as lower nutritional awareness. Children exhibit stronger dietary responses to cold temperatures, which may impact their long-term growth and development. The study also found that older adults were somewhat less sensitive to extreme temperatures, possibly due to reduced appetite. Gender differences in response were minimal.
Projections for the year 2090, based on climate models under the RCP8.5 scenario, suggest that the risk of high-fat diets will increase across most of China, particularly in the southern and eastern regions. In some cities, the probability of adopting a high-fat diet could increase by over 3.9% points. However, widespread use of fans, air conditioners, and heating systems could reduce these effects by nearly half. It is important to note that these projections assume either current levels or complete saturation of adaptation technologies, which may not be fully realized in practice.
Additionally, the projections are based on data from survey provinces and may not capture all regional variations across the country. The study also notes that projections do not account for supply-side changes, such as shifts in food production, and that changing dietary patterns over time may complicate the interpretation of long-term trends. These findings underscore the need for public health strategies incorporating climate adaptation tools to curb the rise of diet-related diseases.
Conclusions
Extreme temperatures influence eating habits by increasing the tendency to consume high-fat diets, even when overall calorie intake remains relatively unchanged. This shift poses serious health risks such as obesity, diabetes, and cardiovascular diseases. The study shows that both hot and cold weather can prompt people to eat more fat, particularly strongly affecting vulnerable groups like rural and low-educated populations. While adaptation tools, such as fans and heating systems, help mitigate these impacts, broader policy interventions are also necessary. The authors also caution that their findings pertain to short-term dietary changes and that further research is needed to understand longer-term impacts. Addressing climate-driven dietary changes is crucial for safeguarding long-term public health in a rapidly warming world.
*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.