The average American eats one ton of food each year.
Literally: It’s a shade under 2,000 pounds.
But one of the most foundational reasons for all that eating is one of the most controllable.
It’s called completion compulsion.
Coined by University of Alabama psychologist Paul Siegel in 1957, completion compulsion describes an uncomfortably familiar eating habit — that we’re more likely to finish what’s on our plate than just stop eating because we’ve gobbled up enough food.
In commenting on the first-ever study of portion size, Siegel wrote that in “cookie consumption, compulsion is marked enough to stimulate a chuckle … On only one occasion was a fraction of a cookie left behind.”
Siegel’s breakthrough was the realisation that we take a meal to be a ‘unit’ of food, and we feel compelled to do everything in our power to finish it.
In the immortal words of Louis CK, “The meal is not over when I’m full. The meal is over when I hate myself!”
Since Siegel’s time, loads of research has been done around how portions relate to eating habits. The science is simple: the bigger the portion, the more people eat.
As Penn State psychologist BJ Rolls described one study,
On five occasions we served men and women an afternoon snack that consisted of 28, 42, 85, 128 or 170 g of potato chips in a plain, unlabeled foil bag.
Participants ate directly from the bag so that they had few visual cues to guide consumption.
The results showed that portion size had a significant effect on snack intake for both men and women.
For example, when served the 170-g package, women ate 18% more and men ate 37% more than when served the 85-g package. As subjects increased their snack intake with increasing package size, they reported feeling fuller; however, they did not adjust their intake at the subsequent dinner to compensate for the increased energy intake.
Similarly, when men and women were served larger portions of a ‘regular’ soda size, women drank 10% and men drank 26% than before.
So what can we do with this info?
Telling people to “eat less” probably isn’t the best approach, Rolls has argued. Instead, she suggests a strategy of eating more foods with a lower “energy density, ” or calorie count. The idea is to eat the same amount of food — you’ll still feel full — but while taking in fewer calories.
The Mayo Clinic says you need to pay attention to three things regarding energy density:
Water. Fruits and vegetables are generally high in water content, which provides volume and weight but not calories. That’s why they’re low-energy-dense foods. Grapefruit, for example, is about 90 per cent water. Half a grapefruit has just 37 calories. Raw, fresh carrots are about 88 per cent water. A medium carrot has only about 25 calories.
Fibre. High-fibre foods not only provide volume, but also take longer to digest, making you feel full longer on fewer calories. Vegetables, fruits and whole grains all contain fibre. Popcorn is a good example of a high-volume, low-calorie whole grain. One cup of air-popped popcorn has about 30 calories.
Fat. Fat is high in energy density. One pat of butter, for example, contains almost the same number of calories as 2 cups of raw broccoli. Foods that contain fat naturally, such as dairy products and various meats, or foods with added fats are higher in calories than are their leaner or lower fat counterparts.
So with a little dietary finesse, you can make completion compulsion work for you. If you have lots of low-energy-dense foods on your plate, you’ll “get full” on things that nourish you.
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