The psychology of eating

The psychology of eating

We reveal how we are tricked into eating, and show you ways to outwit your brain to stop overeating.

You might think you eat when you're hungry and stop eating when you're full, but scientists know better. They know that food labels, plate size, lighting and music, what's on our plate, what the person next to us is doing and our subconscious eating routines, are more likely to influence our eating behaviours than hunger.

These external signals and cues, when added to our not-so-good subconscious habits, encourage us to overeat, which over time adds inches to our waistlines without us even noticing. If we understand why we overeat and how to beat these external influences and create new habits, we can take control of our eating behaviours, weight, and our health.

RESEARCH: See food, eat it!

The phrase 'bottomless bowl' gained new meaning when Brian Wansink and his research team cleverly designed self-refilling soup bowls.

Fifty-four adults were recruited to eat as much free soup as they desired for lunch and fill out a questionnaire – at least that's what they thought. In reality, half the participants were given bowls that secretly self-refilled as soup was pumped up from underneath their table into the bowl as they ate. The other half were given bowls that were openly refilled by waiters.

The participants with self-refilling bowls thought they had eaten the same quantity of soup as the other participants, when in fact, they had
eaten a whopping 73% more! Visual cues affected intake. As long as there was soup in the bowl, the participants kept eating, unaware of
how much they were truly eating.

How our brains trick us into eating more

While we don't want to overeat, the reality is our brains trick us all the time. They tell us to mindlessly follow the same routines at mealtimes – routines that Dr Brian Wansink, in his book Mindless Eating: Why We Eat More Than We Think, calls 'mindless eating scripts'. These ingrained routines tell us when to eat (eg. it's 10am, time for morning tea); what to eat (eg. dinner means meat and three veg); and how much to eat (eg. breakfast means a bowl of cereal, so whether we feel full part way through breakfast or not, we will eat the same sized bowl of cereal every morning).

It takes around 20 minutes for the body and brain to recognise we are full, but most meals in western society are eaten so quickly, they are finished before the 20 minutes is up. Clearly, it isn't satiation of hunger which tells us to stop eating.

Rather than consider whether we're feeling full after each mouthful, we're more likely to trust our eyes and stop eating by judging what's left on our plate.

Our eyes also mislead us. We can't 'see' kilojoules in a meal and we're not good at estimating the size of a meal on sight. Our eyes aren't good judges of food intake and worse, they're easily tempted. Remember the 'see food diet'? If we see food we think about it more. Our bodies then prepare for eating by increasing salivation and hormone production to process food, our hunger increases and consequently, we eat more.

And we don't remember exactly what we've already eaten. Did we have three or four biscuits with our coffee this afternoon? Normal weight adults will underestimate their food intake by 20% while obese people underestimate their intake by 30-40%.

RESEARCH: The 'healthy halo' effect

If a food product says 'low-fat', do you eat more? Probably. In a US study, adults were directed to one of two bowls of unusually coloured M&Ms (gold, teal, purple and white) and invited to help themselves. The bowls were labelled either 'New colours of regular M&Ms' or 'New low-fat M&Ms'.

On average, people ate 28% more of the supposedly low-fat variety.

In another study, researchers asked participants to estimate suitable serving sizes for M&Ms and muesli. Half the participants were told
these were low-fat versions of the food, the others were told they were regular versions. When people saw a food labelled 'low-fat', they estimated an appropriate serving size to be 25% bigger.

These studies found we often assume the energy (kilojoule) content of a food is much less in foods labelled 'low-fat' than they really are.

How our environment can make us fat

It's Murphy's law. The day you decide to adopt a healthier eating pattern, your workmate shouts lunch; or you're unexpectedly given chocolates; or you're served a rather large expensive restaurant dinner you feel obliged to finish. Our environment can be a minefield when it comes to healthy eating intentions. Here's what research tells us:

  • Big packages, servings, and super-sized meals subconsciously suggest big portions are normal.
  • Bigger plates, glasses and serving spoons hold more, so we serve and eat more.
  • Our brains focus on height rather than width. This is known as the horizontal-vertical illusion. We drink more from short, wide tumblers compared to tall, slender glasses.
  • TV is a 'triple eating threat', says Wansink. It encourages snacking, we don't concentrate on how much we eat, and we eat too long.
  • We can't refuse supermarket offers like 'buy two, get one free' and typically buy 30-100% more. And we eat more when it's stockpiled in our cupboards.
  • Convenience costs us. Quick, easy access to food means there is no time to consider how hungry we really are.
  • Drinks before dinner reduce our inhibitions, so we eat more than intended when enjoying a tipple.
  • More food variety encourages overeating as we're biologically programmed to seek food diversity. Having abundant food supplies (eg. in restaurants, pantries and shops) spell trouble.
  • Cooler temperatures, dimmed lighting and soft music all encourage overeating.
  • 'Healthy' restaurant perception can lull us into a false sense of security. Restaurants and fast-food chains with healthy-sounding products and advertising create a 'health halo' – we overeat at these outlets, thinking we can do no wrong.
  • 'Healthy' product perception such as fat-free labels and positive health claims may be amplified by consumers, according to Wansink. Consumers eat up to 50% more of low-fat products.

RESEARCH: How our environment makes us eat more

Distractions during mealtime caused women participating in a French study to eat significantly more than normal. The women were invited to eat lunch in four different laboratory situations in four successive weeks: alone without instruction; alone with instruction on how to eat; alone while listening to a recorded detective story; and at a lunch with all the women together.

The women ate between 200-400kJ more energy during the meal they consumed while listening to the recorded detective story. The researchers believe listening to a story presented sufficient distraction to alter normal eating habits.

Small changes that make a big difference

Deprivation diets don't work as our brains, bodies and environments fight them. A healthy weight-loss is around 1/2 to 1kg per week. So the secret to reaching a healthy weight is making small changes to daily eating habits. Reducing your energy intake by just 400kJ/day could lead to a 4-5kg weight-loss at year's end. Here are some simple changes to make your day at least 400kJ lighter:

  1. Don't have that extra glass of wine. A small 100ml glass has 340-375kJ. Or say no to that extra bottle of beer – a 330ml can or bottle has 400-600kJ.
  2. Use low-fat instead of regular ice cream for dessert. Save about 140kJ on ½ cup; or change to a low-fat yoghurt to save around 240kJ; make it low-fat unsweetened (or artificially sweetened) yoghurt to save about 340kJ.
  3. Have 1/2 cup of pretzels instead of that small bag of chips. Save around 400kJ.
  4. Drink only one trim flat white today. Save 500-550kJ.
  5. Keep your handful of dried fruit and mixed nuts small. Save 700kJ by having 1/4 cup instead of having 1/2 cup.
  6. Instead of pouring oil into the frying pan, measure 1 tablespoon of oil. If it halves your usage, you've saved 520kJ.
  7. Still making vinaigrette the old-fashioned way with 2/3 oil and 1/3 vinegar? Change that ratio to 1/2 and 1/2 to save 170kJ in 2 tablespoons.
  8. Replace 1/4 cup of grated cheddar with 1 tablespoon of more strongly flavoured grated parmesan when making sauces. Save 430kJ.
  9. If you have a large avocado, use 1/4 in your sandwiches rather than 1/2. Save over 600kJ.
  10. Still hungry? Instead of taking another cup of rice, fill yourself up with another cup of low-kJ vegetables. Save over 200kJ.

RESARCH: Menu descriptions affect our choices

Research by Wansink and his colleagues has been taken on board by the food and beverage industry in the US. He provides the example of causal dining chains making menu foods sound more descriptive – with items like 'Succulent Italian Seafood Fillet'  – since their research found more appetising names could increase sales by 23% and make people think the food tasted a lot better.

How to retrain your brain

Habit change 1: Conscious eating

  • Think about whether you are really hungry. Physical hunger appears slowly after a meal, your stomach rumbles, and the sensation disappears after eating. Emotional hunger involves cravings and often isn't satisfied by eating.
  • Consciously decide how much to eat before you start your meal.
  • Cut your portions but not too much. Reducing the size of your meal by 1/5 will mean you eat less, but you won't notice nor feel deprived.
  • Eyeball your food. Whatever the meal, put all the food you plan to eat on your plate instead of picking from serving dishes on the table. Then you can see and understand the quantities.
  • Don't spoil healthy choices by adding unnecessary high-fat/sugar accompaniments.
  • Be the last person to start eating at meals, and put your knife and fork down between bites.
  • Save empty treat wrappers as a reminder of how many treats you have eaten over the day/week.
  • Create food trade-offs or food policies, suggests Wansink. For example:
    – Tell yourself, "I can have dessert only if I take a 30-minute walk first." (ie. a food trade-off.)
    – "I can have a latté on Monday, Wednesday and Friday, herbal teas on other days."
    – "I can only eat snacks away from my work desk." (This gives you time to reconsider your desire.)
    – Swap fruit juice and dried fruit snacks for fresh fruit (ie. set yourself a food policy).
  • Eat more slowly. Ways to do this:
    – Use chopsticks.
    – Eat using utensils in your non-dominant hand.
    – Chew your food 30-50 times each mouthful.
    – Eat sitting down.
    – Make a healthy-sized plate of food last 20 minutes.
    – Pace yourself with the slowest eater at the table.
  • Think outside the square. For example, order an entrée and side salad instead of an over-sized main when dining out.

    RESEARCH: The horizontal-vertical illusion

Even professionals in the food service industry are fooled by the size and shape of plates, bowls and glasses.

Researchers recruited 45 experienced US bartenders to pour single-shot drinks of gin, whiskey, rum and vodka with the proviso that the bartenders weren't allowed to use a measuring device or pouring spout.

Half the bartenders were given tall, thin glasses, and the other half were given short, wide tumblers. They were then required to manually pour one shot of spirits into their assigned glasses. Even the researchers were shocked by the results. The bartenders consistently poured an average 27% more spirits into the short, wide tumblers compared with tall, slender glasses.

Habit change 2: Set up a 'no-fail' environment for weight-loss

We subtly gain weight and we can lose it the same way – by making small changes to our environment. It's much easier to change our environment than our mind. Try these techniques:

  • Use smaller plates and bowls. They discourage overeating.
  • Keep treat and snack foods out of sight and out of mind. Seal in non-transparent containers and place on top shelves of the pantry. Wrap tempting leftovers in tinfoil and store at the back of the fridge.
  • Use tall, slim glasses rather than short, wide tumblers.
    Place healthy, low-energy foods at the front of the pantry and fridge.
  • Use smaller serving spoons so you'll take smaller servings.
  • Make snacking inconvenient. Put snack and treat foods somewhere you have to get up and walk to – or better still, don't have them in the house, so if you really want a treat, you have to go out to get it.
  • Repackage foods from large boxes and packets into smaller zip-lock bags, and hide spare packets at the back of the cupboard.
  • Replace the cookie jar on the kitchen bench with a fruit bowl.
  • Avoid temptation. Don't drive past the takeaway shop, don't walk through the kitchen, turn off the TV to avoid food adverts – develop a plan to avoid your weaknesses.
  • Make eating 'seconds' inconvenient. Leave serving dishes in the kitchen – the walk from the table deters overeating.
  • Don't eat in front of the TV, computer or while reading. Eat at the dinner table, on a plate.

RESEARCH: Convenience rules!

Easy access to chocolates proved irresistible for US office workers. When researchers placed chocolates on the desks of office workers, the workers ate an average of 5.6 more chocolates each day than if the chocolates were placed two metres away on another table.

Habit change 3: Cope with danger foods

Danger foods are different for everyone – they can range from chocolate to crackers! But if we deny ourselves something, we crave it more – be it food or relaxation. Our bodies and minds fight against food deprivation and our environment conspires to make it a losing battle. Instead, try these coping strategies for your danger foods:

  • Embrace your danger food. Eat it slowly, savour it, be conscious of every mouthful and don't feel guilty.
  • Face the danger head-on. Try this brave technique before you indulge: Imagine your doughnut or pie, picture what it tastes like and how you will feel after you have eaten it. Then think: do I really want it? If yes, savour it consciously. If you're not sure, tell yourself you will see doughnuts again, so you can enjoy one another time.
  • Go for quality not quantity. Love cheese? Choose a couple of slices of a creamy, dreamy brie over half a block of reduced-fat cheese. If wine's your temptation, invest in smaller glasses and a lovely wine stopper and have a glass of water at the same time.
  • Only eat danger foods outside the home. Eat a muffin at a café rather than taking a packet home, for example.
  • Plan for danger times. If your danger foods are party snacks, plan ahead. Have a small healthy meal or substantial snack before you go out and stand well away from the nibbles when you are there.
  • 'De-convenience' danger foods. Wrap the tempting food in extra packaging, box up and store away. Repackage foods like chips and nuts into small serving sized zip-lock bags for storage. These are now the 'official' serving size.
  • Find other ways to treat yourself. When you have done well or achieved one of your goals, do something nice for yourself. Make the time to catch up with a friend, get your hair cut, have a massage or buy a new magazine and some flowers.

RESEARCH: Super-sized stale food

Any chocolate-lover can tell you buying a smaller bar is the easiest way to control how much chocolate you are going to eat. But surprisingly, studies show if we're given a bigger portion of an unappetising food, we still manage to chomp our way through more.

Researchers randomly gave movie-goers either a medium-sized or large-sized bucket of stale popcorn. These people had all eaten dinner before attending the movie, so they weren't hungry. Still, the people given the large bucket consumed 35% more of the popcorn. And the popcorn was 14 days old!

Small but satisfying snacks

Chocolate>Low-fat chocolate drinkORChocolate dairy foodORSmall portion like Whittaker's dark chocolate squares


Handful of dried fruit and nutsORBerries (fresh or frozen)ORCouple of fresh dates
Potato chips


Roasted chickpeasORPita or bagel crispsORPopcorn
Sweet mega muffin


Slice whole grain fruit loafORWhole gain toast with honeyORLow-energy muesli bar


Author: Jennifer Bowden

Healthy Food Guide

First published: Sep 2008

2017-04-03 17:20:15

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