Former NASA scientist Ray Cronise was watching Michael Phelps in the 2008 Olympics when the broadcast said Phelps consumed 12,000 calories per day. Cronise calculated that even if Phelps swam three hours a day and had a superior metabolism, he would still have not been in a good shape given his diet. But soon Cronise figured it out. Since Phelps was spending hours every day in the water, his body was burning additional calories just to keep its core temperature stable.

Soon, Cronise was doing everything he could to incorporate cold into his life. In six weeks he lost 27 pounds without altering his caloric-restrictive diet. Given all the variables, cold exposure’s effect on fat-loss is difficult to research scientifically. Still, studies have shown that cold exposure can boost someone’s metabolism by 8 to 80 percent to burn fat depending on degrees of water, duration, diet, age, gender, and fat mass.

Additional testing is being done to get more precise variables. It is believed that the fat loss in cold water comes for brown adipose tissue, or BAT. Once thought of as to only exist in animals, recent studies show a prevalence of BAT fat cells in humans. Normal fat tissue just stores calories. BAT cells burn calories to produce heat. If the effects of cold-water exposure are real, BAT fat cells are the reason.

And some studies have found that these cells continue to burn fat after the subjects exit the pool. Even then, the body is burning calories to get back to its normal temperature.

The proof is there that more fat is lost when working out in cold water. And as we’ve shown, the pool is a great place to workout. There are infinite techniques to stay fit. So the question is, why wouldn’t you take advantage of cold exposure and burn more fat while working out in the pool?