Testing an online measure of portion size selection: a pilot study concerned with the measurement of ideal portion size

BackgroundPortion 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.MethodsIn 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.ResultsSupporting 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,).ConclusionsPilot 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

‘Edible seaweeds’ as an alternative to animal-based proteins in the UK: Identifying product beliefs and consumer traits as drivers of consumer acceptability for macroalgae

Edible macroalgae (i.e., ‘seaweeds’) are a nutritious and sustainable alternative to animal-based proteins. However, consumption of seaweeds in Western countries remains low, and little is known about individual drivers of acceptance. The aim of this study was to further explore the consumer acceptability of seaweed-based food products in the UK. In an online study (N = 476), participants were presented with a general description of edible seaweeds, and descriptions of seaweed-based food products (e.g., ‘seaweed burger’). Participants were asked to rate beliefs about product attributes, and reported acceptance in terms of liking, willingness to try, willingness to buy, and readiness to adopt as a meat alternative. It was predicted that positive beliefs about seaweed-based products would be significantly associated with greater acceptance, and that seaweed-based products would be more favourable than a general description of seaweeds. Supporting study hypotheses, structural equation modelling showed that positive beliefs about taste/ edibility and familiarity significantly predicted acceptance (p .05). These results support the consumer acceptance of seaweeds, and identify scope for utilising specific attributes of seaweeds (as drivers of acceptance) in future product development

Consumer perception of food variety in the UK: an exploratory mixed-methods analysis

Background: ‘Food variety’ is a key term that is frequently used in dietary guidelines around the world. Consuming a variety of foods – be it within a meal, across meals, or as part of the whole diet – is one factor that has been shown to increase food intake. However, little is known about consumer understanding of variety, and this may be a potential barrier to the success of dietary guidelines in today’s ‘obesogenic’ environment. This research sought to explore 1) consumer recognition of different forms of variety, and 2) consumer definitions of variety. Methods: In an online study (N = 240), participants were asked to discuss a range of photographs depicting different forms of variety, and to directly define the term ‘food variety’. They were unaware of the research aim. Results: Using a mixed methods approach, directed content analysis of these data showed that individuals referenced multiple forms of variety in the presence of food photographs. However, when asked to define variety, participants tended to only discuss variety in the context of the whole diet. Conclusions: These findings emphasise a need to educate consumers about variety to encourage adherence to dietary guidelines and help consumers better manage their own food intake

Food-variety-focused labelling does not increase ideal portion size, expected fullness or snack intake

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

Effect of food variety on intake of a meal: a systematic review and meta-analysis

A systematic review and meta-analysis exploring the effect of food variety on food intake (the variety effect)

Exploring the association between dietary variety and weight

This project will further investigate the relationship between dietary variety and weight at a population level, using secondary data from the UK Biobank. Specifically, this project aims to; 1) Understand the relationship between dietary diversity scores (derived from 24-hr recall questionnaire) and weight (BMI/body fatness) at a population level, considering the role of energy density as a moderator (see H4 for details on moderation). H1: Higher dietary diversity scores will be associated with a higher BMI/body fatness at a population level, and this will be moderated by energy density (directional) 2) Understand the relationship between the perception of dietary variety (the individual's rating of variety in their diet) and weight (BMI/body fatness) at a population level, considering the role of energy density as a moderator (see H4 for details on moderation). H2: Higher subjective ratings of dietary variety will be associated with having a higher BMI/body fatness at a population level, and this will be moderated by energy density (directional) 3) Examine the role of portion size selection as a potential mediator in the relationship between dietary variety and weight, considering the role of energy density as a moderator (specific portion size items from survey data will be used to indicate a tendency to choose smaller/larger portions across the diet) (see H4 for details on moderation). H3: Portion size selection will mediate the relationship between dietary variety and weight, as it is moderated by energy density; higher dietary diversity scores will be associated with having a higher BMI/body fatness when individuals report a tendency to choose larger portions, when energy density is high. This constitutes a moderated mediation. (directional) 4) Examine the role of energy density as a potential moderator in the relationship between dietary variety and weight (energy density of foods consumed will be derived from 24-hr recall dietary questionnaire data) H4: Energy density will moderate the relationship between dietary variety and weight; higher dietary diversity scores will be associated with having a higher BMI/body fatness when individuals report a tendency to consume high energy dense foods. Likewise, higher dietary diversity scores will be associated with having a lower BMI/body fatness when individuals report a tendency to consume low energy dense foods. (directional) For a full outline of the project, see the supplementary materials

Exploring the conceptualisation of ‘variety’ and its effects on food intake: A mixed methods approach

‘Food variety’ is a dietary factor with a potentially double-edged influence on consumer health. Though variety is known to support diet quality, it is also recognised as a contributing factor to overconsumption, and variety remains a concept requiring further refinement in the literature. The overarching aim of this thesis was to explore the conceptualisation of variety and its effects on food intake. Chapter 1 provides a narrative review of theoretical frameworks relevant to the concept of variety, and Chapter 2 presents a systematic review and meta-analysis of experimental studies that have explored effects of variety as a driver of meal intake. Results supported a small-to-medium effect, but highlighted significant heterogeneity across studies. Chapter 3 includes findings from two qualitative studies focussed on the consumer understanding of variety. Results showed that consumers have an awareness of variety when discussing hypothetical preferences, but that participants generally defined ‘variety’ only in the context of the whole diet. Chapters 4 and 5 further explored effects of variety within foods, specifically when measuring portion size selection using a novel online tool. Though no significant differences were found across levels of variety, key methodological issues specific to investigating effects of composite foods were highlighted. Chapter 6 reports effects of dietary variety on body weight using prospective data from the UK Biobank. Dietary variety was a significant predictor of portion size. There was also some evidence of a significant, negative association between dietary variety and body weight, though portion size as a mediator and energy density as a moderator did not significantly influence this relationship. Overall, this thesis supports variety as a robust driver of food intake. Results provide novel insight into the conceptualisation of variety from a researcher and consumer perspective, highlighting implications for tailoring future research focussed on variety to the modern eating environment