Influence of meal congruency with food reward on energy intake during passive acute cold and heat exposure: a randomised controlled trial
This randomized controlled trial demonstrates that serving a meal temperature congruent with the environment (specifically a cold meal in hot conditions) can mitigate the heat-induced reduction in energy intake, whereas meal congruency did not significantly affect intake during cold exposure.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
For soldiers on long missions and athletes pushing their limits, the body is a machine that burns fuel at a high rate. Keeping this machine running requires eating enough to match that burn, but the environment often gets in the way. When the air is freezing or scorching hot, the body has to work harder just to stay at a safe internal temperature, which changes how much energy is needed. At the same time, extreme temperatures can trick the brain into wanting less food, or changing what kind of food feels appealing. If a person burns more calories but eats less because they are too hot or too cold, they risk running out of energy, which can hurt their ability to think clearly or move effectively. Scientists have long known that cold weather often makes people want to eat more, while heat tends to suppress appetite, but the reasons behind these shifts are complex. It is not just about feeling hungry; it is also about how much the brain rewards the idea of eating something specific, like a hot soup versus a cold salad, depending on the weather outside.
A team of researchers set out to test a simple idea: could serving food at a temperature that matches the weather help people eat enough when they are in extreme conditions? They gathered thirty healthy adults and placed them in a large, climate-controlled room that could be set to feel like a chilly day, a comfortable room, or a hot summer afternoon. The participants spent six hours in these conditions, wearing the same light clothing in each session to ensure the temperature was the only variable changing. Half the group was given a cold meal to eat, while the other half received a warm meal. The food itself was very similar in ingredients and nutrition, just served at different temperatures, roughly six degrees Celsius for the cold group and sixty degrees for the warm group. Before they ate, the researchers measured how much the participants wanted the food and how hungry they felt, tracking these feelings every thirty minutes.
The results showed that the weather did indeed change how much people ate, but the temperature of the meal mattered greatly in the heat. When the room was hot, the group eating the warm meal ate significantly less than they did in comfortable conditions. This drop in eating matched their reported lack of hunger. However, the group eating the cold meal in the same hot room did not reduce their food intake at all. Even though they felt less hungry, the fact that their food was cool and matched the hot environment seemed to keep them eating a normal amount. In the cold room, the story was different. Both groups ate more than they did in the comfortable room, regardless of whether their food was served cold or warm. The cold weather seemed to trigger a strong drive to eat more calories that overrode the temperature of the food itself.
This suggests that in hot environments, the temperature of the food can act as a lever to control how much a person eats. When the food feels right for the weather, like a cool dish on a hot day, it can prevent the natural drop in eating that usually happens in the heat. This is important because it offers a practical way to help people maintain their energy levels when they are working or training in high temperatures. In cold weather, the body's need for extra energy seems so strong that it pushes people to eat more no matter what they are served, but in the heat, matching the meal to the climate might be the key to avoiding a dangerous energy deficit. The study did not find a single biological switch that explains why this happens, but it clearly shows that the simple act of serving a meal at the right temperature can change how much fuel a person takes in.
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