Prevention of the Portion Size Effect

An increase in the portion size leads to an increase in energy intake, a phenomenon which is also referred to as the portion size effect. The increase in portion sizes in recent years is regarded as an important contributor to the increase in the prevalence of obesity. Hence, the aim of this thesis is to better understand why the portion size effect occurs and what can be done to prevent it.
We found that one of the reasons why people rely on the portion size when determining how much to eat, is because it is an indicator of what others will find an appropriate consumption quantity. To prevent the portion size effect, we explored whether it would be effective to remind diet-concerned people of their dieting goal. Such a reminder motivates diet-concerned people to control consumption, which makes it less likely that they will use the portion size as an indicator of how much they can eat. We indeed found that this reminder prevented the portion size effect. Finally, we showed that provision of a pictorial serving size recommendation can also weaken the portion size effect. A serving size recommendation provides people with an alternative reference point to rely on when determining their consumption amount, and hence they don’t need to rely on the portion size.
We conclude that with sufficient help, people will be able to rely less on environmental cues, such as the portion size, when making consumption decisions.