The portion size effect and overconsumption – towards downsizing solutions for children and adolescents

Portion sizes of foods offered to consumers have increased at the same time as overweight and obesity levels have risen. It has been suggested that large portions of high energy density (HED) foods increase total energy intake and that this is not compensated for in the short- to medium-term, potentially promoting weight gain. In the laboratory setting, offering large portions of HED foods increases overall energy intake in both children and adults. This phenomenon is known as the portion size effect (PSE), and it is robust, reliable and enduring. The possible impact of the PSE is that large portions served over time may facilitate overeating and could contribute to overweight and obesity. Explanations for the PSE vary from simple heuristics, such as the tendency to clear the plate, to more complex biobehavioural processes, including individual differences in susceptibility to external food cues through eating traits. Consumers may eat in accordance with available consumption norms or eat opportunistically when large portions are made available. An obvious solution to the PSE is to ‘downsize’ HED meal items and snacks, but whether this strategy is acceptable or feasible is not clear. In adults, the effects of downsizing are mixed and for children and adolescents, as yet unclear. The contention is that for those who are still learning about social norms and appropriate portions, there remains the potential to counter the PSE through downsizing strategies.