Winter swimming, i.e. swimming in ice-cold water, is not only a wonderful method of tempering the body, but also of increasing the energetic might of the organism.
Nutrition and Appetite
There are suggestions that swimming doesn't cause the same drop in appetite that accompanies heavy running and cycling training. Many people feel extremely hungry after training in the pool, and may simply replace all the calories they've burned with a large post-exercise meal. "Many people observe that they feel like 'eating a horse' after they have finished a swim training session, and may overcompensate for the energy they have just burned." "Some research suggests that this is due to the cool temperatures in which swimmers train. By contrast, runners and cyclists usually experience an increase in body temperature during training, which may serve to suppress appetite - at least in the short term." In one recent study, researchers examined the effect of water temperature on calorie intake after exercise . A group of 11 men exercised for 45 minutes in "neutral" and "cold" water temperatures. After the workout, they were allowed to eat as much food as they wanted. The men burned a similar number of calories in the cold and neutral water conditions, averaging 505 and 517 calories, respectively. However, calorie intake after exercise in the cold water averaged 877 calories, which was 44% more than for the neutral temperature. The problem here is that the water temperature during the "cold" condition was extremely cold (60 degrees F), and isn't really indicative of the water temperature of most pools (which is usually nearer 80 degrees F).
Professor Louise Burke, Head of Nutrition at the Australian Institute of Sport, also points out that competitive swimmers typically have body fat levels that are higher than those of runners or cyclists who expend a similar amount of energy when they train.
Professor Burke also points out that swimmers are less active outside their training sessions. They are so tired from the hours spent training that they sleep, sit or otherwise avoid any real physical activity outside their sessions. In one study, researchers compared collegiate swimmers and collegiate distance runners, the runners had lower body fat levels than swimmers. However, detailed three-day food records and one-day activity records offered no convincing explanation as to why.
Coach Pedro H. Ordenes, ASCA