During Ramadan, many fasting people complain of feeling cold, even if the weather is mild or even hot. This is explained by the laws of physics governing heat and energy in the human body. The human body always tries to maintain a constant temperature (36.1–37.2°C), because biological enzymes work efficiently only within this narrow range. This is achieved through a balance between heat generated by the body and heat lost due to environmental factors. The heat generated by the body comes mainly from the food we consume. Nutrients such as carbohydrates, fats, and proteins are converted into chemical energy during digestion. Part of this energy is used to power the body's cells, and the other part is converted into heat that keeps the body warm. The heat lost is controlled by several physical mechanisms, as explained in a research article published by the U.S. National Institutes of Health. These are 'radiation,' which means the body emits electromagnetic waves carrying heat to the surroundings; 'convection,' which means heat transfers from the skin to the surrounding air when air or fluids move around the body; 'conduction,' which means heat transfers when the skin touches a colder surface like the ground, a chair, or water; and finally 'evaporation,' when water evaporates from the skin or during respiration, taking some heat with it. While the balance between the heat generated internally by the body and the heat lost through these four mechanisms occurs automatically, what happens during fasting is that heat generation sources decrease, while all heat loss methods continue, leading to the fasting person feeling cold even in warm weather. Many studies have documented this change that causes a feeling of cold, including those published in the 'Clinical Nutrition' journal, which showed that carbohydrate consumption decreased and stabilized at a low level on the second day of fasting, and also revealed a decrease in the total average energy consumed over 24 hours during fasting compared to the usual eating period. Although this feeling of cold might seem negative at first glance, the same study considers it a positive change that supports the body's health. As carbohydrate consumption decreases, the body gradually shifts to using fat as a primary energy source. These metabolic changes can enhance the body's metabolic flexibility, improve insulin sensitivity, and increase the efficiency of the body's 'power plants,' the mitochondria. That is, the cold felt by the fasting person is a temporary symptom in exchange for long-term health benefits that improve the body's vital functions in a way that supports health and longevity.
