Watching 90 minutes of adrenaline-pumping terror can use up as much as 113 calories, close to the amount burned during a half-hour walk and the equivalent to a chocolate bar.
A study at the U.K.'s University of Westminster (yes, sometimes they do study such things) measured the total energy expenditure of 10 people as they watched a selection of frightening movies. Scientists recorded their heart rate, oxygen intake and carbon dioxide output - and discovered the number of calories used increased by a third on average during the films.
The research also revealed films featuring moments designed to make viewers jump in terror are the best calorie-burners, as they cause heart rates to soar.
The top calorie burners:
Read more from the Telegraph.