Right Sizing: Sensory-Based Product Design Is a Promising Strategy to Nudge Consumers toward Healthier Portions

Systematic review of the portion size norm of discretionary foods

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.

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Portion size selection in children: Effect of sensory imagery for snacks varying in energy density

Food sensory imagery - creating a vivid mental image of the sensory experience of eating - can lead to the selection of smaller portions because it serves as a reminder that eating enjoyment does not necessarily increase with portion size. The evidence is mostly limited to adults and to energy-dense foods for which it is particularly difficult to predict the satiating effects of consumption quantity. The objective was to study how food sensory imagery influences portion size selection of foods varying in energy density (brownie and applesauce) by 7- to 11-year-old children. During after-school time, 171 children were randomized into two conditions. Children in the food sensory imagery condition were asked to imagine the taste, smell, and texture of eating palatable foods, i.e., chocolate cereal, chocolate waffle, and chocolate candies. Children in the control condition performed a similar sensory imagery task for non-food-related activities. Children were then asked to choose between the recommended serving size, a 50% larger portion, and a 125% larger portion of either brownie or applesauce. One week later, they were placed in the same condition for the other food. Compared to the control condition, food sensory imagery led children to choose 7.1% less brownie but had no effect on applesauce portion selection. Exploratory findings showed that the food sensory imagery intervention was especially effective at reducing brownie portion size selection among children who were moderately hungry, who usually eat fast, and whose parents pressure them to eat. In conclusion, food sensory imagery may be a useful intervention to nudge children towards healthier portion size choices because it reduces the selected portion size of an energy-dense snack without reducing the selected portion size of a healthier snack.