Portion distortion

by Jennifer Bowden / 12 November, 2015
One easy way to reduce your food intake is to change your crockery.
The Last Supper of Christ by Santacroce. Photo/Thinkstock
The Last Supper of Christ by Santacroce. Photo/Thinkstock


Can you afford to eat another chocolate or not? In reality it’s almost impossible to estimate how much food we can consume in a day without packing on the kilos. So instead we use a range of subconscious cues to guide our intake, such as package and plate size and the amount others are eating.

But these aren’t an accurate measure, and in the past few decades, the size of standard food servings and dinner plates has grown. That’s led to changes in perceptions of what’s considered a normal ­portion size – or portion distortion.

Not even Christ and his disciples were immune to the phenomenon. Analysis of depictions of the Last Supper – Da Vinci’s 15th-century painting is one of the most famous – dating from about 1000AD to the present, found the main course had increased in size by nearly 70%, and the bread and plates had grown by 23% and 66% respectively.

Overeating is common these days, resulting in increased risk of heart disease, diabetes and cancer. The extent to which larger portions are to blame has been the subject of much research. Most studies have found people eat more when given bigger servings or plates.

But one New Zealand clinical trial found plate size did not affect energy intake among a group of 20 overweight and obese women. What’s more, portion sizes here are almost certainly smaller than those in the US, where much of this research has been done.

However, New Zealand has its share of portion-related problems. A study this year in Public Health Nutrition, for example, found our sweetened-beverage package and serving sizes are larger than those of Australia, Canada and the Netherlands. Another found extreme variations in energy and fat content between countries: McDonald’s New Zealand Chicken McNuggets had 21.1g of fat per 100g, more than many other countries and almost double Germany’s 12g.

Scientists at the behaviour and health research unit at Cambridge University combined the results of 61 studies involving more than 6700 participants to investigate the influence of portion, package and tableware size on food intake.

Their analysis showed people consistently ate and drank more when given larger portions, packages or tableware than when offered smaller servings. They estimate smaller portions could decrease average daily energy intake from food by 12-16% among UK adults (about 1167kJ) or 22-29% among US adults (up to 2205kJ).

Review co-leader Gareth ­Hollands says the findings cast new light on the tendency to portray personal characteristics such as being overweight or a lack of self-control as the main reason people overeat.

“In fact, the situation is far more complex. Our findings highlight the important role of environmental influences on food consumption. Helping people to avoid ‘over­serving’ themselves or others with larger ­portions of food or drink by reducing their size, availability and appeal in shops, restaurants and in the home, is likely to be a good way of helping lots of people to reduce their risk of overeating.”

Portion, packaging and tableware sizing affected food intake irrespective of body weight, gender or eating behaviour, the review found. So we’re all potentially influenced by these external factors.

Meanwhile, the most accurate food intake gauge we have – our appetite – often ends up ignored, although some cultures are more adept at using internal cues. French women are often envied for their ability to eat rich foods and not gain weight. Researchers have found some startling differences in eating cues when comparing the eating habits of American and French adults. The French are more likely to report that they stop eating when they start to feel full, wanting to leave room for dessert or simply that they no longer feel hungry. In contrast, Americans use more external cues, stopping eating when others thought it was normal (not a good idea when over one-third of Americans is obese), or when they run out of a beverage, or the tele­vision show they are watching is over.

There are many reasons some countries have less of an obesity problem than the US, but differences in eating cues are a likely contributor. But knowledge is not power in this situation, according to the ­researchers. Even when university graduate students were given a 90-minute lecture on the effect of serving sizes and how to overcome this influence, six weeks later they still overconsumed snacks served in a larger bowl versus a smaller bowl. That points to the importance of environmental change to alter food cues and the need to relearn how to listen to appetite cues.

Enough’s enough


•  Use smaller bowls, plates and spoons. Dust off your grand­parents’ dinner set, which is likely to be more modestly sized than modern ones.

•  Serve main portions such as meat and pasta in advance in the kitchen but dish up veges and salads at the table.

•  Use scales or cups to measure serving sizes of rice, pasta, cereals and milk. Failing that, judge meat servings, for instance, by your palm size.

•  Eat slowly, which allows time for your stomach to signal your brain that it’s full. If you eat quickly, you’ll overeat before you know it.

•  Eat mindfully – at the table without distractions such as the TV, phones or computers.

•  You don’t have to finish everything on your plate. Forget what your parents said – if you’re full, stop eating.

•  Never eat directly from a ­package, as you’re likely to eat up to 30% more than you would from a plate. The bigger the package the more we’ll eat.

•  Buy food that’s packaged into portion-controlled sizes.

•  Repackage bulk foods into single servings in zip-lock bags or similar.

•  Choose small portions when eating out – if you buy more you’ll eat more. The “share plates” trend can be helpful to reduce intake.

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