Heat loss is controlled in two ways:
1. Insulation - body fat plus clothing and
2. Environmental factors - temperature, wind and wheather you are exercising in the air or in the water.
Each of these two factors plays a role in the body's ability to maintain a comfortable temperature during exercise.
Although many people aspire to have a lean figure, people with a little more body fat are better insulated and will lose less heat. Clothing adds to the insulation barrier and is clearly the most important element in performance and comfort while exercising in the cold.
Clothing is generally a good insulator because it has the ability to trap air, a poor conductor of heat. If the air trapped by the clothing cannot conduct the heat away from the body, temperature will be maintained. Unlike air, water is a rapid conductor of heat. Even in the coldest of temperatures, people will sweat and risk significant heat
loss. With this in mind, choose clothing that can trap air but allow sweat to pass through.