Science Interviews


Tue, 9th Sep 2014

Can Bruce Willis make you gain weight?

Aner Tal, Cornell University

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Obesity is a growing problem across the world, but some of our eating habits Popcorncould be influenced by the type of TV we are watching. Aner Tal, from Cornell University in the US, looked at how much food volunteers ate while watching either an action-packed movie or a sedate talk show. He explained to Chris Smith how our watching and eating habits are closely linked... 

Aner -   Being distracted by watching TV can lead people to eat more.  What we wanted to find out is, if different TV content can lead people to eat more or less, depending specifically on how dynamic the content was or how engaged they are with the content.

Chris -   So literally, TV consumption can affect food consumption.

Aner -   Yeah.

Chris -   In what way?

Aner -   Basically, your attention is limited.  So, the more you're paying attention to what you're watching on the TV, the less you're paying attention to what you're eating.  So, if you're watching something that’s very absorbing, you can just go on eating without realising it.

Chris -   So, how did you do the study?

Aner -   We randomly divided participants into three groups and each group watched 20 minutes of programming.  One group was given a segment of the action movie “The Island.”  Another group was given a segment of the talk show, the “Charlie Rose Show” which is a fairly laid back, relaxed conversation type of talk show.  The third group was given the same segment from “The Island” but without sound.  Each person watching the shows was given an amount of snacks they had in front of them and they could eat while they're watching the shows.  And when they were done watching the show was, we measured how much they had eaten.

Chris -   What came out of it?  What did you find?

Aner -   People watching the action movie ate more snacks than people who were watching the talk show.  Even people who watch the action movie without sounds still ate considerably more than people watching the talk show.  So, they are 46% more calories, even watching the action movie without sound.  With sound, they ate 65% more calories.

Chris -   How many calories did they burn because it was exciting?

Aner -   I don’t think it works that way?  I wish we could just watch like exciting TV or a sports TV and that would be our exercise.

Chris -   Was it genuinely that there's something about the content or the way that the programming works that makes people compulsively eat?

Aner -   I think so.  So, we’re still doing some follow up investigations to get a more precise idea of what the process is, but you can, to some extent, have divided attention or shift your attention.  But if you're completely absorbed in something, then it’ll be much more difficult to pay attention to something else.  So, if you're watching TV, you're not watching what you eat.

Chris -   And does this in some way subvert your brain’s circuitry which logs how many calories are going in and tells you to stop eating?

Aner -   I would say, more than that, it’s your paying attention to how you're feeling.  So, kind of getting that feeling that you know, “I've had so much chips, I already kind of feel like throwing up, so maybe I should stop.”  If you're not paying attention to how you're feeling, you can just continue eating on automatic.

Chris -   Is there a relationship between sex – I don’t mean the physical act of sex.  I mean, gender and this effect.  Do you see that men or women are more susceptible?

Aner -   Yeah, so I mean, there's probably a relation between the physical act of sex as well but…

Chris -   The reason I asked this is because obviously, we know that men find certain types of action movie more compelling than women.  If I turn on a thriller, my wife will often fall asleep whereas I’ll still be watching it at midnight.  So, is there a sex susceptibility in this effect, do you think?

Aner -   We do think so and that’s one of the initial pieces of evidence we got from this study that gives us a hint about what's going on because there was a bit higher consumption for males watching the action film than for females.  So, it had more of an effect of them and that might be because it engaged their attention more.

Chris -   So, what would your recommendations be to people who are traipsing off to the cinema or to their home cinema, armed with a box of popcorn?

Aner -   Leave the box of popcorn at home.  No, I think it’s partly about controlling how you'll act when you're unconscious.  So, just assume you're going to go into a movie coma, you're going into something that you're going to be swallowed up in and either get a healthy snack.  That way, you'll be eating baby carrots versus chips or chicken wings.  Or just restrict the quantity you have.  So, just have a pre-determined amount and then you know that’s what you're going to eat because that’s what you have.  Even you can have a situation where you have more if you want to, but you'll need to actually go for the effort of getting up walking all the way to the kitchen which will also burn a lot of calories and getting more.  And setting things up that way versus just having a huge amount in front of you is going to prevent some of this mindless eating trap.

Chris -   So basically, make the fridge really hard to open so you'll at least burn some calories retrieving the supplementary salts.

Aner -  Yeah, you'll do aerobic activity walking to the fridge and then you'll build your muscles opening it.  Yeah, that’s a good idea.


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There has to be a reason why advertisers pay to sponsor television. I have a vague suspicion that it is because it influences our behaviour. The alternative explanation, that advertisers are even more stupid than their audiences, is improbable. alancalverd, Tue, 9th Sep 2014

The explanation given in the report "Can Bruce Willis make you gain weight" do not sound convincing to me. If the film were taking the attention of the subject, then surely they would pay less attention to eating. Isn't another possibility that because the action movie is more fast paced, the subject's perception of time is sped up. They eat more frequently, but they don't realise it - they feel that they're eating at a constant rate. RussellJones, Thu, 11th Sep 2014

Hi Russell

That's correct - the argument put forward by Aner Tal to account for the effect is that the action movie is more engaging - or distracting - and therefore renders a person less sensitive to their own internal physiology, including satiety signals. The result is a greater tendency to overeat. chris, Sat, 13th Sep 2014

I'm saying that it's nothing to do with satiety. If I eat one crisp, I'm not satiated, but that doesn't mean that I would eat another one immediately. I would wait a period of time, and then I might have another, but I'm still not satiated. In a movie I'm not going to be looking at my watch - I make an unconscious estimate of the amount of time that has elapsed. But it is known that people's perception of time is based on the number of events that are experienced. In a state of sensory deprivation, time appears to pass much more slowly than in a highly stimulated state. So, during an action movie time may seem to pass more quickly, and this would make the viewer eat more frequently (in absolute time). Obviously they would reach satiation sooner (again, in absolute time), but it's not clear from the report whether the tests were long enough for that to actually happen.
In any case, if the subjects did reach satiety but kept eating anyway, would one not expect them to report some discomfort once the viewing had finished? RussellJones, Sat, 13th Sep 2014

They watched for 20 minutes. If they had begun to reach the "i feel really sick" stage then the effect would have saturated so the interval was set to 20 minutes to catch everyone in the active-eating phase.

The researchers didn't assess behaviourally why the subjects ate more, or their sensations of hunger or otherwise. That may well be the topic of a future paper. chris, Sun, 14th Sep 2014

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