According to HowStuffWorks.com, laughing and smiling burn calories. It explains that every action, including automated body functions like breathing or the heart's beating as well as voluntary actions like walking results in burning calories. HowStuffWorks.com further states that the body burns calories even while sleeping or resting.
According to the Vanderbilt University Medical Center, laughing and smiling lead to an increase in the heart rate. As the heart rate increases, the metabolism increases as well, so laughing and smiling result in increased energy consumption. The research conducted by Vanderbilt University Medical Center revealed that 10 to 15 minutes of laughing can burn between 10 to 40 calories.