Systematic review of the portion size norm of discretionary foods

Abstract

Context Portion size norm is described as the perception of how much of a given food people choose to eat. Reducing the portion size norm of foods that are high in saturated fat, added sugar, and added salt toward smaller sizes might be a potential strategy to promote appropriate portion size selections. However, an overview of existing portion size norms for discretionary foods has yet to be established. Objective The aim of this systematic review was to examine the portion size norm of discretionary foods and assess the methodologies used to investigate the norm. Data Sources The literature search was conducted in 6 databases following the PRISMA guidelines (from inception to January 2022). Data Extraction Forty studies were eligible and grouped into 3 categories by portion size norm measures: normal (n = 26), appropriate (n = 8), and preferred portion sizes (n = 3). Study quality was assessed using the Joanna Briggs Institute Critical Appraisal Tools. Data Analysis A wide range of portion sizes were considered normal for each food type, with means/medians varying from 2- to 4-fold among studies. Studies differed considerably in design, with variables including the setting, food type, food presentation, the manner in which portion-size-related questions were formulated, and the range and number of displayed serving size options. The quality of reviewed studies was mixed (25 studies had low or moderate risk of bias, 15 had high risk of bias), and the method of assessing portion size was not validated in 15 of 33 quantitative studies. Conclusion The assessment of portion size in future studies should be conducted using tools that are validated for the population of interest so that more definitive conclusions can be drawn regarding portion size norms for discretionary foods. Systematic Review Registration PROSPERO registration number CRD42021249911.

Differences between the normal and perceived appropriate portion sizes of discretionary foods

“…It should be noted that serving sizes that are considered as being 'too small' potentially trigger additional intake through consuming further servings and compensatory eating at later meals [14,15]. To avoid unintended consequences, the proposed "norm range model" suggests a range of portion sizes may be considered as normal; offering serving sizes within, but at the lower end, of this range might reduce intakes unconsciously [16,17]. Nevertheless, there is a lack of knowledge and limited data on normal portion sizes (described as the portion size people would usually or typically consume at one sitting) versus perceived appropriate portion sizes (described as the portion size people consider to be an appropriate amount to be consumed at one sitting) for common discretionary foods [17,18].…”

“…Consumers' normal portion sizes may re ect their usual or typical intake based on past experiences [20]; whilst the perceived appropriate portion sizes seemed to be more closely related to social norms in terms of 'the expected amount to be consumed according to others' [20,25]. However, inconsistent de nitions of these concepts have been used, and some studies regarded the 'normal' and 'appropriate' portion size as alternative terms [17,30]. Currently, there is scant data on the extent to which the normal and perceived appropriate portion sizes overlap or differ from each other, as well as whether people "normally" consume more than the amount they consider as appropriate.…”

Development and validation of an online tool to assess perceived portion size norms of discretionary foods

“…Perceived portion size norms, described as a typical perception of how much of a given food individuals choose to eat at a single eating occasion [ 1 , 2 ], have a key role in food consumption and portion control behaviours [ 3 , 4 ]. This norm may have been distorted towards larger sizes due to the ubiquity of large serving and package sizes currently available in the food environment [ 5 , 6 ].…”

“…Different types of perceived portion size norms have been identified in previous research [ 1 , 2 ]. For example, individuals might be guided by social norms of portion sizes (that is, beliefs about how much others expect them to eat) when dining out with a group, while personal norms of portion sizes (that is, beliefs about how much to eat according to oneself) may be more salient when eating alone in a home setting [ 1 , 12 ].…”

Development and validation of an online portion size norm assessment tool

“…(2,3) Portion size norms for common EDNP foods have yet to be established, and there is currently a lack of validated tools to assess the norm. (4) Therefore, the aim of this study was to develop and validate an online image-based tool to investigate the portion size norm of commonly consumed EDNP foods among Australian consumers. An image series survey including 15 EDNP foods and drinks such as sweet and savoury snacks, cakes, fast foods, and sugar-sweetened carbonated drinks was developed using Qualtrics.…”