well, I was thinking like this. ...cold water once enters the body needs to be heated up. The body would require a certain amount of calories to burn to heat up the cold water, hence burning more energy.

Another line of thought went like ... if you eat food with cold water, the body will have to devote more energy to reheat the cold food in your stomach before digestion can take place. Also since it's cold, the food in the stomach will take longer to be digested.