Smaller portions recalibrate the 'normal' amount to eat

Although previous research has established the effect that portion size has on food intake, the UK scientists, publishing their findings in the American Journal of Nutrition​, said this is the first study looking at the effect of exposure to small portion sizes has on future eating.

Human eating behaviour and appetite control is flexible and there is no precise ‘correct’ amount to eat, wrote the researchers from the University of Liverpool's Institute of Psychology, Health and Society.

Therefore, they wanted to determine whether reducing the size of food portion can recalibrate the perception of what constitutes a normal amount of that food to eat, and if this would result in people selecting and consuming smaller portions in the future.

They found that eating a smaller portion size of a food resulted in participants believing a ‘normal’-sized portion was smaller, consuming less of that food one day later and displaying a tendency toward choosing a smaller ideal portion of that food one week later, although the latter finding was not significant.

Lead author Dr Eric Robinson said: "There have been suggestions that shrinking the portion size of commercially available food products could be one approach to reducing overconsumption and tackling population-level obesity.​

"The present findings indicate that if portion sizes of commercially available foods were reduced, these smaller, more appropriate portion sizes may recalibrate perceptions of what constitutes a ‘normal’ amount of food to eat and, in doing so, decrease how much consumers choose to eat."​

However, co-author Inge Kersbergen said it was unclear from the study how long the effect would last for in real-life conditions.

“The effects we observed were larger when we examined food intake the next day in the laboratory than when we looked at portion size preference one week later.​

"Based on the idea that our immediate environment influences our perceptions of what a normal portion size is, it is likely that the effect would only last if we encounter smaller portion sizes more often than supersized portions."​

Study details ​

In the first leg of the three-part study, which was partly funded by the American Beverage Association and Unilever, female participants were served either a large (200 g, 440 kcal) or small (100 g, 220 kcal) portion of a broccoli and tomato quiche at lunchtime. The next day at lunchtime, after completing an unrelated word task as a ‘cover’, they were allowed to serve themselves from a tray with large portions of the same quiche.

In the second experiment, this was repeated with male participants and, in the third, the researchers tested asked the group of 64 men and women on their preferred ideal portion size of that food after one week.

Source: American Journal of Clinical Nutrition ​

“Portion size and later food intake: evidence on the “normalizing” effect of reducing food portion sizes”​

Published online ahead of print 9 April 2018, doi.org/10.1093/ajcn/nqy013​

Authors: Eric Robinson and Inge Kersbergen