Daily life: It is obviously easier to lose weight when the weather is hot, because as LZ said, when the weather is hot, especially when sweating, the metabolism of the human body will increase a lot. When the temperature is low, although a certain metabolism is needed to maintain the body temperature, other functions of the body consume less energy at this time, and measures such as not wearing thick clothes can't keep warm in cold weather, so generally speaking, the metabolism in cold weather is slower than that in hot weather, so it is easier to lose weight in hot weather.
The influence of hot and cold food on obesity is even less, even negligible. The heat (temperature) brought into the body by hot food does not actually make people fat, because what people usually call "heat" of food is not the concept of temperature.
Cold food really needs to reach a certain temperature to interact with the corresponding digestive enzymes, just like LZ said, but the metabolism required to heat this food can be ignored, so the impact of food cold and hot on obesity is almost zero.