Every year around late October, a number surfaces again: 113 calories, apparently the amount you burn sitting through a horror film, roughly what a short walk would cost you. It arrives dressed as science, gets shared as a fitness curiosity, and disappears until the next Halloween. It has been doing this for well over a decade. The figure is real, in the sense that someone once measured something. The trouble is what people take that measurement to be.

What the number actually came from

The source is a 2012 exercise run at the University of Westminster in London, supervised by Dr Richard Mackenzie, a senior lecturer in cell metabolism and physiology. Researchers measured the heart rate, oxygen intake and carbon dioxide output of ten people while they watched a selection of frightening films, and calculated energy expenditure from those readings. The reported average worked out to around 113 calories across a roughly 90-minute film, which the coverage compared to a half-hour walk or a small chocolate bar.

The films at the top of the list burned more. The Shining came first at an average of 184 calories, followed by Jaws at 161 and The Exorcist at 158, per the figures carried by UPI in October 2012. Films built around frequent jump scares tended to score higher, which fits the stated mechanism: a sharp fright lifts the pulse, and the associated adrenaline briefly raises the metabolic rate.

Worth flagging, since the phrasing has drifted over the years: a good deal of the recirculated coverage says viewers burned “up to 113 calories,” then lists several films above that figure in the same breath. The 113 was the average, not the ceiling. That is a small slip, but it is the kind that happens when a statistic is copied rather than read.

Who paid for it, and why the timing matters

The experiment was commissioned by LOVEFiLM, the UK movie-rental service later acquired by Amazon, and released just ahead of Halloween. The company’s editor at the time was quoted encouraging viewers to keep their eyes on the screen rather than hide behind a pillow, framing that reads more as a nudge toward renting films than as a research conclusion.

The study appears never to have been peer-reviewed or formally published, a point Snopes made in its review of the claim. That does not mean nothing was measured. The work was done at a genuine institution under a genuine specialist, and the physiology it describes is unremarkable: fear raises heart rate, and a raised heart rate burns marginally more energy. But a commercial commission, a sample of ten, and no publication is a long way from the settled finding the number is usually presented as.

What it does and doesn’t support

Taken on its own terms, the result is modest and roughly plausible. Sitting through a tense film will cost you slightly more energy than sitting through a calm one. Nobody needs a laboratory to find that credible.

None of this makes it a weight-loss method, and the original work never claimed otherwise. A hundred-odd calories is a biscuit. The 113 is also an average drawn from ten people watching specific films on a specific day, which says little about what any one person would burn on their sofa. The stat has survived not because it is important but because it is pleasant, letting a night in front of the television borrow a little of the language of exercise.

Why it keeps coming back

The more durable story here has little to do with calories, and everything to do with how a seasonal marketing statistic hardens into a permanent fact. A rental company wanted attention in the week before Halloween, so it paid for a small measurement, attached a real university’s name to it, and released a shareable figure at exactly the moment editors were looking for something spooky and light. The number did its job, then kept working long after the company that commissioned it was folded into Amazon.

The stat resurfaced again in October 2025, still framed as a study, still rounded to the same 113, in outlets that did not exist when the measurement was taken. Nobody along the way set out to mislead anyone. The number simply outlived the small print that came with it, which is how most of these things last.