Why did I eat that?!?

What we eat isn’t just about hunger or our taste buds.  There are hundreds of environmental cues that influence what and how we eat.  Brian Wansink is a Professor at Cornell University who comes up with super interesting experiments to answer just that question.  Here are some of my favourites:

The tomato soup experiment

Participants were invited to a restaurant for lunch.  All were given tomato soup, but unbeknownst to them, 50% of the bowls were slowly and imperceptibly being refilled as they were eating.  Not only did the people who were eating from the self-refilling bowls eat 73% more soup than those eating from normal bowls but frighteningly, they didn’t believe they had consumed more than anyone else at the table and they also reported the same amount of satiety as those eating from normal bowls.

Brian Wansink with his bottomless bowl.

Brian Wansink with his bottomless bowl.

The message: In Brian’s words, “people use their eyes to count calories and not their stomachs”.  The wisdom of our body’s mechanisms being able to tell us through feedback loops when we are full are fooled by visual cues.  The majority of us (in the US) eat until we clean our plates.  Our eyes influence how much we consume (because what’s on our plate is a portion, right?) and how full we feel may have more to do with how much we believe we ate and less to do with how much we actually ate.


The popcorn experiment

For this experiment Wansink went to the movies and gave movie-goers free popcorn in either medium or large containers.  The popcorn eaters who were given the bigger containers ate over 45% more popcorn – but get this, the really surprising thing is the container size influence is so powerful that even when stale popcorn was put in larger containers (and the participants said they weren’t hungry) 34% more was eaten from a bigger container.  Even when foods are not palatable, large packages and containers can lead to overeating.

The message: we overeat foods we have (not necessarily foods we want).  Not only is this a good reminder that if we’re going to have junk food go for the smallest possible portion but this phenomenon can be used in reverse for increasing consumption of healthy foods.  Want to increase your kids’ vegetable consumption?  Increase their vegetable portion sizes.

The candy experiment

A bowl of chocolate kisses was rotated around an office.  Participants ate twice as many chocolates when the kisses were placed on their desk than when they were 6 feet away and had to walk to get them.  Whilst both the visibility and the convenience of the chocolates significantly contributed to how many were consumed, convenience (ie, being in close proximity) contributed more to over eating them than visibility did.  The participants were also more likely to lose track of how many they had eaten when the bowl was located at arm’s length.

The message: keep food off the desk and out of reach at dinner time.

Slide 1

The ice cream experiment

Participants were invited to an ice cream social, given bowls and spoons of different sizes and told to help themselves to ice cream.  Those with larger bowls and spoons not only served themselves more but also ate more.

The message: Use large plates for veggies if you need to increase your healthy food consumption and use small plates for dessert (if you are going to have it at all).  Moving from a 12-inch to a 10-inch dinner plate leads people to serve and eat 22% less

Why the French are skinnier than Chicagoans

Parisians and Chicagoans were surveyed and asked how they knew they were done eating.  The French said they knew they had finished their meal when the food no longer tasted good or were full.  The Americans said they knew they were done eating when their plate was empty, the group they were eating had finished or the TV show they were watching was over.

The message:  You’re more likely to maintain a healthy weight if you learn to be influenced by internal cues instead of using external cues to know when to stop eating.


Other super interesting Wansink finds

  •  Low fat labels lead people to eat 16-23% more total calories
  • You’re 30% more likely to eat the 1st thing you see when you open the fridge or cupboard (so stock your fridges and cupboards wisely!)
  • 50% of the snack food bought in bulk is eaten within six days of purchase
  • The average person makes over 250 decisions about food in a day
  • A person will eat on average 92% of any food they serve themselves
  • Both children and adults will drink 76% more out of a short, wide glass than a tall narrow glass of the same volume (but perceive the opposite to be true)
  • If the buffet costs more you eat up to 42% more

Slide 1I wouldn’t fall for that!

 A commonality in the outcomes of these studies is that we think we are better at self monitoring than we are.   The bottomless bowl soup eaters didn’t think they had eaten any more than the people with the normal bowls; the office candy consumers lost track of how many they had when the bowl was within reach; some of the participants in the ice cream experiment were nutrition experts (and not immune to serving themselves more ice cream in the bigger bowl) and a movie-goer who had happily munched down more popcorn than the claimed “I wouldn’t fall for that!”.

We think we are better at self monitoring than we are.  Whilst knowing about these traps helps reduce our perceived vs actual consumption we still wrongly think we can self monitor to overcome bias more effectively than we actually can.

Learning to pay attention to when your body has had enough is easier said than done.  Start by using the visual cues such as smaller plates, serving smaller portions not going back for seconds or leaving food within sight and reach.  Also try to make meal times as relaxing as possible, slow down, turn off the tv, try to stop at the “I could eat more” stage rather than the “I’m stuffed stage”, and remember you don’t need to finish everything on your plate.

Want to read more from Brian Wansink?  www.mindlesseating.org and he’s He’s also the author of: Mindless Eating: Why We Eat More Than We Think (2006) New York: Bantam-Dell.


Wansink B, Painter J.E, North J (2005) Bottomless Bowls: Why Visual Cues of Portion Size May Influence Intake.  Obesity Research. 13:1 (January) 93 – 100

Wansink B, Junyong Kim (2005) Bad Popcorn in Big Buckets: Portion Size Can Influence Intake as Much as Taste.  Journal of Nutrition Education and Behaviour.  37:5 (Sept – Oct) 242 – 245

Wansink B, Cheney M (2005) Super Bowls: Serving Bowl Size and Food Consumption.  Journal of the American Medical Association, 293:14 (April) 1727-1728

Painter J.E, Wansink B, Hieggelke J.B (2002) How Visibility and Convenience Influence Candy Consumption.  Appetite, 38:3 (June) 237-238


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6 Responses to Why did I eat that?!?

  1. Fascinating post, thanks, Leaping Zucchini. Not mentioned in this particular post is sugar. I believed my switch off mechanism to indicate fullness was faulty – I could recall only a few times in my life in which I felt full and consequently had to work out portion size with my eyes (as per the research cited here). Heavily reducing sugar in the diet has activated the fullness switch for the first time in my life. I will also bear in mind the information here!

    • I totally agree and there is a lot of science that has been done around just that. Not just sugar but also sweeteners and other chemicals and additives have been shown to cause havoc with our normal systems too. Interestingly though, in these studies showed similar results across different BMIs (body mass indexes), gender and age so that suggests that it’s more than just junk food addiction that can cause us to overeat. It’s also a reason why tomato soup was chosen in the soup bowl research – it’s not something that typically we would think we over eat. Unlike popcorn, candy and ice cream in the other studies mentioned there.

  2. VJ says:

    This was really interesting.

    I got sucked in by the bulk order one the other day – really felt like a chocolate bar (yeah yeah, I know…!) and it was 1 bar for $2 or 5 bars for $4 – no prizes for guessing the rest of the story, dammit!

  3. blizzard in denver says:

    I had onion rings, 4 beers and a greek salad for dinner last night. I did feel full after that, and the plate was empty. I guess in that case there was agreement between my taste buds, gut feel and eye-meter?

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