Originally published 2018-11-14.
Watching a horror film does make your body use a little more energy, but not enough to count as a weight-loss method. The often-quoted figures come from a small 2012 test at the University of Westminster in London, commissioned by the film rental service LOVEFiLM, in which ten volunteers watched ten scary films while researchers measured their heart rate and breathing. On average each film burned about 113 calories, with Stanley Kubrick's The Shining topping the list at 184. It is a fun result with a real physiological basis, but it was a publicity study, not peer-reviewed research.
Jack Nicholson as Jack Torrance in The Shining (1980), Kubrick's adaptation of the Stephen King novel. In the 2012 test it produced the biggest jump in energy use of any film, roughly 184 calories over its running time.
What the test measured
The work was supervised by Dr Richard Mackenzie, a senior lecturer at the University of Westminster who specialises in cell metabolism and physiology. Volunteers were monitored while they watched, and the team tracked three things: heart rate, the amount of oxygen breathed in, and the amount of carbon dioxide breathed out.
Measuring gases in and out of the lungs is a standard way of estimating energy use, called indirect calorimetry. Because the body uses oxygen to burn fuel and releases carbon dioxide as a by-product, the volume of those gases can be converted into an estimate of calories used per minute. Comparing a film's viewing period with a calm baseline gives the extra energy spent.
According to the results reported at the time, energy use rose by about a third while people watched the films. Mackenzie said that "each of the ten films tested set pulses racing", and the biggest increases came during sudden jump scares.
The ten films and their calorie counts
These are the figures released with the study, in calories per film:
- The Shining: 184
- Jaws: 161
- The Exorcist: 158
- Alien: 152
- Saw: 133
- A Nightmare on Elm Street: 118
- Paranormal Activity: 111
- The Texas Chain Saw Massacre: 107
- The Blair Witch Project: 105
- [Rec]: 101
Two things are worth noticing. First, the numbers are totals for whole films of different lengths, so a longer film has an advantage: The Shining runs well over two hours, while [Rec] is under 80 minutes. Second, the list mixes slow-burning dread with shock-heavy films, and the press material suggested that jump scares were what really raised heart rates.
Shelley Duvall's terrified scream from The Shining, one of the most recognisable scenes in horror. Moments like this, where tension suddenly peaks, are exactly where the volunteers' heart rates climbed most.
Why fear makes the body burn more energy
The explanation is the body's stress response. When the brain detects a threat, even one it knows is on a screen, it triggers the "fight or flight" system. The adrenal glands release adrenaline, the heart beats faster and harder, breathing speeds up, and muscles tense in readiness to move. All of that costs energy, so for a short time the metabolic rate rises above its resting level.
Mackenzie also suggested that a burst of adrenaline can briefly dampen appetite. That fits what we know about acute stress, but the effect is short-lived, and the study did not measure what volunteers ate afterwards. Anyone who has finished a horror film and headed for the fridge will have their doubts.
Fear is not the only emotion that does this. Excitement during a close sports match, a tense thriller or a video game can also raise heart rate. Horror just does it reliably, which is part of why the genre is so popular.
Pennywise the clown from the 2017 film It, based on another Stephen King novel. It was not part of the 2012 test, which was carried out years before the film's release, but it is a good example of the kind of modern horror that relies on sudden scares.
Putting 113 calories in perspective
An extra hundred or so calories per film sounds impressive in a headline. In practice, it is small. The fact-checking site Snopes pointed out that a person weighing about 150 pounds burns roughly 100 calories just sitting still for an hour and a half, so the figures should be read as total energy used during the film, not pure extra burn. If energy use rose by about a third, the true bonus from being scared is only a few dozen calories per film.
That is easily cancelled out by snacks. A sugary drink or a handful of sweets during the film can contain more calories than the fright burns, and a large tub of cinema popcorn can contain many times more.
Common myths about the "horror diet"
- "Science proves horror films help you lose weight." No. The test measured short-term energy use in ten people. It did not track body weight over time, and there was no comparison with other activities.
- "It was a university study, so it was peer-reviewed." It was carried out at a university, but it was commissioned by a film rental company and released just before Halloween. It does not appear to have been published in a scientific journal, and it has not been replicated.
- "Scarier films always burn more." Not necessarily. Film length, how familiar the viewer is with the film, and individual sensitivity to fear all affect the numbers. Someone who loves horror and feels relaxed watching it may barely react.
- "Fear-induced adrenaline is a healthy workout." A racing heart caused by stress is not the same as exercise. It does not build fitness or strength.
The takeaway
The 2012 experiment is a neat demonstration of how strongly the body reacts to fear, even when we know we are safe on the sofa. It is not a reason to swap a walk for a film marathon. If you are worried about your weight or your health, the right person to talk to is a doctor. If you simply enjoy a good scare, you can watch The Shining knowing that your heart is working a little harder than usual, and that the jump scares are doing more for your pulse than for your waistline.
Sources: ShortList: Watching The Shining burns 184 calories; Snopes: Does watching horror movies help you lose weight?; GIPHY: The Shining scream.
COMMENTS