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Background Portion size is known to be a key driver of food intake. As consumed portions are often pre-planned, ‘ideal portion size’—an individual’s preferred meal size selected prior to eating—has been identified as a strong predictor of actual consumption. However, assessments of ideal portion size have predominantly relied on laboratory-based computer tasks, limiting use online. Therefore, this cross-sectional study sought to pilot test the validity of a web-based tool to measure ideal portion size. Methods In an online study (N = 48), participants responded to images of a range of foods. Each food was photographed in a series of different portions and loaded into an ‘image carousel’ that would allow participants to change the size of the displayed portion by moving a slider left-to-right. Using this image carousel, participants selected their ideal portion size. They also completed measures of expected satiety and expected satiation and self-reported their age and body mass index (BMI). A non-parametric correlation matrix was used to explore associations between ideal portion size and identified predictors of food intake. Results Supporting convergent validity of this measure, ideal portion size was significantly correlated with expected satiety (rs = .480) and expected satiation (rs = −.310) after controlling for effects of baseline hunger and fullness, consistent with past research. Similarly, supporting divergent validity of this measure, ideal portion size was not significantly correlated with age (rs = −.032) or BMI (rs = −.111,). Conclusions Pilot results support the validity of this web-based portion size selection tool used to measure ideal portion size, though further research is needed to validate use with comparisons to actual food intake.

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Background Many studies have shown that food variety—the presence of multiple foods and/or sensory characteristics within and across meals—increases intake. However, studies report mixed findings, and effect size remains unclear. Objectives A systematic review and meta-analysis were conducted to 1) synthesize data across experimental studies that examined effects of variety on total meal intake, relative to a control condition with comparatively less variety; 2) quantify support for this effect; and 3) assist in the identification of important moderating factors (registration: CRD42019153585). Methods In November 2019, we searched the following databases for relevant experimental studies, published in English from 1980, with human participants: PubMed, Cochrane Library, Web of Science, ClinicalTrials.gov, PsycINFO, and OpenGrey. This search was updated in September 2020. Means, standard deviations, and sample sizes were extracted from included articles, and Hedges' g was used to calculate effect sizes. Risk of bias was assessed using the Cochrane Collaboration's tool. Results Of 7259 references identified in an initial search, 34 articles consisting of 37 studies contained sufficient information for review, and data from 30 studies (39 comparisons) were included in the meta-analysis. Results from a random-effects model showed a significant small to medium effect of variety on intake (in weight and energy), with greater variety being associated with increased consumption (Hedges' g = 0.405; 95% CI: 0.259, 0.552). However, heterogeneity was considerable across studies (I2 = 84%), and this was unexplained by subgroup analyses based on form of variety, test foods, sensory characteristics, age, sex, and body weight. Conclusions Our findings support the conclusion that variety is a robust driver of food intake. However, risk of bias was high across studies, and this review highlights methodologic limitations of studies. It is recommended that further attention is given to the development of preregistered, well-powered randomized controlled studies in eating behavior research.

As greater food variety has been shown to increase intake and is associated with a higher BMI, interventions that modify the effects of food variety have implications for combatting obesity. Previous research has shown that labelling a food with ‘high variety’ flavour-specific labels can reduce an individual’s satiation whilst eating. We were interested in whether the effects of ‘variety labelling’ would also be observed on portion size selection and ad libitum food intake. Therefore, two studies were conducted to explore the effects of labelling foods with different levels of variety on ideal portion size, ratings of expected fullness, and actual intake. In Study 1 (N = 294), participants viewed images of a range of foods that were presented with either high variety labels (descriptions of within-food components), low variety labels (general names of food items), or no label. They selected their ideal portion size and rated their expected fullness for each food. In Study 2 (N = 99), they also consumed one of these foods ad libitum. It was hypothesised that foods presented with high variety labels would have an increased ideal portion size, reduced expected fullness, and increased intake compared to foods presented with low variety labels or no label. Our findings failed to support these predictions, and we found no evidence of an effect of variety labelling on ideal portion size, expected fullness or food intake. These findings highlight the importance of considering how consumer research studies translate to a more ‘real world’ setting.