Real-world nudging, pricing, and mobile physical activity coaching was insufficient to improve lifestyle behaviours and cardiometabolic health: the Supreme Nudge parallel cluster-randomised controlled supermarket trial.

BACKGROUND: Context-specific interventions may contribute to sustained behaviour change and improved health outcomes. We evaluated the real-world effects of supermarket nudging and pricing strategies and mobile physical activity coaching on diet quality, food-purchasing behaviour, walking behaviour, and cardiometabolic risk markers. METHODS: This parallel cluster-randomised controlled trial included supermarkets in socially disadvantaged neighbourhoods across the Netherlands with regular shoppers aged 30-80 years. Supermarkets were randomised to receive co-created nudging and pricing strategies promoting healthier purchasing (N = 6) or not (N = 6). Nudges targeted 9% of supermarket products and pricing strategies 3%. Subsequently, participants were individually randomised to a control (step counter app) or intervention arm (step counter and mobile coaching app) to promote walking. The primary outcome was the average change in diet quality (low (0) to high (150)) over all follow-up time points measured with a validated 40-item food frequency questionnaire at baseline and 3, 6, and 12 months. Secondary outcomes included healthier food purchasing (loyalty card-derived), daily step count (step counter app), cardiometabolic risk markers (lipid profile and HbA1c via finger prick, and waist circumference via measuring tape), and supermarket customer satisfaction (questionnaire-based: very unsatisfied (1) to very satisfied (7)), evaluated using linear mixed-models. Healthy supermarket sales (an exploratory outcome) were analysed via controlled interrupted time series analyses. RESULTS: Of 361 participants (162 intervention, 199 control), 73% were female, the average age was 58 (SD 11) years, and 42% were highly educated. Compared to the control arm, the intervention arm showed no statistically significant average changes over time in diet quality (ߠ- 1.1 (95% CI - 3.8 to 1.7)), percentage healthy purchasing (ß 0.7 ( - 2.7 to 4.0)), step count (ߠ- 124.0 (- 723.1 to 475.1), or any of the cardiometabolic risk markers. Participants in the intervention arm scored 0.3 points (0.1 to 0.5) higher on customer satisfaction on average over time. Supermarket-level sales were unaffected (ß - 0.0 (- 0.0 to 0.0)). CONCLUSIONS: Co-created nudging and pricing strategies that predominantly targeted healthy products via nudges were unable to increase healthier food purchases and intake nor improve cardiometabolic health. The mobile coaching intervention did not affect step count. Governmental policy measures are needed to ensure more impactful supermarket modifications that promote healthier purchases. TRIAL REGISTRATION: Dutch Trial Register ID NL7064, 30 May 2018, https://www.onderzoekmetmensen.nl/en/trial/20990.

Changes in UK price disparities between healthy and less healthy foods over 10 years: An updated analysis with insights in the context of inflationary increases in the cost-of-living from 2021.

Food prices and affordability play an important role in influencing dietary choices, which in turn have implications for public health. With inflationary increases in the cost-of-living in the UK since 2021, understanding the dynamics of food prices becomes increasingly important. In this longitudinal study, we aimed to examine changes in food prices from 2013 to 2023 by food group and by food healthiness. We established a dataset spanning the years 2013-2023 by combining price data from the UK Consumer Price Index for food and beverage items with nutrient and food data from the UK nutrient databank and UK Department of Health & Social Care's National Diet and Nutrition Survey data. We calculated the price (£/100 kcal) for each food item by year as well as before and during the period of inflationary pressure, and classified items into food groups according to the UK Eatwell Guide and as either "more healthy" or "less healthy" using the UK nutrient profiling score model. In 2023, bread, rice, potatoes and pasta was cheapest (£0.12/100 kcal) and fruit and vegetables most expensive (£1.01/100 kcal). Less healthy food was cheaper than more healthy food (£0.33/100 kcal versus £0.81/100 kcal). Before the inflationary pressure period (from 2013 to late 2021), the price of foods decreased by 3%. After this period, the price of food increased by 22%: relative increases were highest in the food group milk and dairy food (31%) and less healthy category (26%). While healthier foods saw smaller relative price increases since 2021, they remain more expensive, potentially exacerbating dietary inequalities. Policy responses should ensure food affordability and mitigate price disparities via, for example, healthy food subsidies.

The moderating role of eating behaviour traits in the association between exposure to hot food takeaway outlets and body fatness.

BACKGROUND: Previous studies demonstrated a relation between takeaway outlet exposure and health outcomes. Individual characteristics, such as eating behaviour traits, could make some people more susceptible to the influence of the food environment. Few studies have investigated this topic. We aimed to investigate the moderating role of eating behaviour traits (cognitive restraint, uncontrolled eating and emotional eating) in the association between neighbourhood exposure to hot food takeaway outlets (hereafter referred to as takeaway outlets), and takeaway food consumption and adiposity. METHODS: We used cross-sectional data from a cohort in Cambridgeshire, UK (The Fenland study). Takeaway outlet exposure was derived using participants' residential address and data from local authorities and divided into quarters. The Three Factor Eating questionnaire (TFEQ-R18) was used to measure eating behaviour traits. Primary outcomes were consumption of takeaway-like foods (derived from food frequency questionnaire), and body fat percentage (measured using dual-energy X-ray absorptiometry). RESULTS: Mean age of participants (n = 4791) was 51.0 (SD = 7.2) and 53.9% were female. Higher exposure to takeaway outlets in the neighbourhood and higher eating behaviour trait scores were independently associated with greater takeaway consumption and body fat percentage. Uncontrolled eating did not moderate the associations between takeaway outlet exposure and takeaway consumption or body fat percentage. The association between takeaway outlet exposure and takeaway consumption was slightly stronger in those with higher cognitive restraint scores, and the association between takeaway outlet exposure and body fat percentage was slightly stronger in those with lower emotional eating scores. CONCLUSION: Eating behaviour traits and exposure to takeaway outlets were associated with greater takeaway consumption and body fat, but evidence that individuals with certain traits are more susceptible to takeaway outlets was weak. The findings indicate that interventions at both the individual and environmental levels are needed to comprehensively address unhealthy diets. TRIAL REGISTRY: ISRCTN72077169.

Impact of taxes on purchases of close substitute foods: analysis of cross-price elasticities using data from a randomized experiment.

OBJECTIVE: To examine the effects of health-related food taxes on substitution and complementary purchases within food groups, including from unhealthier to healthier alternatives and between brands. METHODS: We used data from a virtual supermarket experiment with data from 4,259 shopping events linked to varying price sets. Substitution or complementary effects within six frequently purchased food categories were analyzed. Products' own- and cross-price elasticities were analyzed using Almost Ideal Demand System models. RESULTS: Overall, 37.5% of cross-price elasticities were significant (p < 0.05) and included values greater than 0.10. Supplementary and complementary effects were particularly found in the dairy, meats and snacks categories. For example, a 1% increase in the price of high saturated fat dairy was associated with a 0.18% (SE 0.06%) increase in purchases of low saturated fat dairy. For name- and home-brand products, significant substitution effects were found in 50% (n = 3) of cases, but only in one case this was above the 0.10 threshold. CONCLUSIONS/POLICY IMPLICATIONS: Given the relatively low own-price elasticities and the limited substitution and complementary effects, relatively high taxes are needed to substantively increase healthy food purchases at the population level. TRIAL REGISTRATION: This study included secondary analyses; the original trial was registered in the Australian New Zealand Clinical Trials Registry ACTRN12616000122459 .

Are nudging and pricing strategies on food purchasing behaviors equally effective for all? Secondary analyses from the Supreme Nudge virtual supermarket study.

Nudging and pricing strategies are effective in promoting healthier purchases. However, whether the effects are equal across individuals with different personal characteristics is unknown. This exploratory study aimed to examine differential effects of nudging and pricing strategies on food purchases across individuals' levels of impulsivity, price sensitivity, decision-making styles, and food choice motives. Data from a virtual supermarket experiment where participants were exposed to five study conditions (control, nudging, pricing, salient pricing, and salient pricing with nudging) was used. Participants completed questionnaires assessing their impulsivity, price sensitivity, decision-making styles, and food choice motives. The outcome was the percentage of healthy food purchases. Effect modification was analyzed by adding interaction terms to the statistical models and post-hoc probing was conducted for statistically significant interaction terms. We used data from 400 Dutch adult participants (61.3% female, median age 30.0 years (IQR 24.0)). The effects of the nudging and pricing conditions on healthy food purchases were not modified by impulsivity, price sensitivity, decision-making styles, and the food choice motives 'health' and 'price'. Only the interactions of the food choice motive 'natural content of foods' x pricing (B = -1.02, 90%CI = -2.04; -0.01), the food choice motive 'weight control' x nudging (B = -2.15, 90%CI = -3.34; -0.95), and 'weight control' x pricing (B = -1.87, 90%CI = -3.11; -0.62) were statistically significant. Post-hoc probing indicated that nudging and/or pricing strategies were more effective in individuals who gave lower priority to these food choice motives. The effects of nudging and pricing strategies on increasing healthy food purchasing behaviors, at least in a virtual environment, do not seem to be influenced by personal characteristics and may therefore be implemented as general health promoting strategies.

The effects of nudging and pricing on healthy food purchasing behavior in a virtual supermarket setting: a randomized experiment.

BACKGROUND: Evidence on what strategies - or combination of strategies - are most effective and equitable in promoting healthier diets is needed. This study examined the efficacy of nudging and pricing strategies on increasing healthy food purchases and the potential differential effect by socio-economic position (SEP) among Dutch adults in a virtual supermarket. METHODS: A randomized study design was conducted within a virtual supermarket (SN VirtuMart). Participants were exposed to five within-subject study conditions (control, nudging, pricing, price salience and price salience with nudging) and randomized to one of three between-subject study arms (a 25% price increase on unhealthy products, a 25% discount on healthy products, or a 25% price increase and discount). In total, 455 participants of low and high SEP (using either education or income as proxy) were randomized to conduct their weekly shopping in a virtual supermarket for five consecutive weeks. The primary outcome included the percentage of healthy purchases. Data were analyzed using linear mixed models. RESULTS: In total, 346 (76%) adults completed all five shops within the SN VirtuMart. Median age was 32.5, 49.2% had high education and 32.8% had high income. Out of the 12 conditions, four conditions were statistically significantly different from the control condition. Nudging and non-salient pricing strategies alone did not statistically significantly increase healthy food purchases, whereas a combination of salient price increases and discounts led to an increase in the percentage of healthy food purchases (B 4.5, 95%CI 2.6; 6.4). Combining salient pricing and nudging strategies led to increases in the percentage of healthy products in all three pricing arms, with largest effects found in the combined price increase and discount arm (B = 4.0, 95%CI = 2.0; 6.0). Effects were not modified by SEP. CONCLUSIONS: Combining health-related price increases and discounts and combining these salient pricing strategies with nudges in a supermarket setting seems to stimulate healthy food purchases for both low and high SEP populations. However, further research in real-world settings is needed. TRIAL REGISTRATION: This randomized trial ( NTR7293 ) was registered in the Dutch trial registry ( www.trialregister.nl ).

To what extent do dietary costs explain socio-economic differences in dietary behavior?

BACKGROUND: Low socio-economic position is associated with consumption of lower quality diets, which may be partly explained by the cost of healthier diets. Therefore, we aimed to investigate the mediating role of dietary costs in the association between educational level and diet quality. METHODS: We used cross-sectional data from Dutch older adults (N = 9399) in the EPIC-NL cohort. Participants provided information about their own and their partners' highest attained educational level (as proxy for socio-economic position). Dietary behavior was assessed using a food frequency questionnaire from which we derived two diet-quality scores, including the Dutch Healthy Diet index 2015 (DHD15-index) and the Dietary Approaches to Stop Hypertension (DASH) diet. Dietary cost estimates were based on food price data from food stores, and linked to reported consumption of food items. Multiple regression analyses and bootstrapping were used examine the mediating role of dietary cost in the association between educational level and diet quality. RESULTS: Mean age of participants was 70 (SD: 10) years and 77% were women. Dietary costs significantly mediated the association between educational level and diet quality, except for high versus middle individual educational level and the DHD15-index. Depending on the dietary and educational indicator, dietary costs explained between 2 and 7% of the association between educational level and diet quality. Furthermore, associations were found to be modified by sex and age. For the DHD15-index, mediation effects were only present in females and adults older than 65 years, and for the DASH diet mediation effects were only present in females and strongest amongst adults older than 65 years compared to adults younger than 65 years. CONCLUSION: Dietary costs seems to play a modest role in explaining educational differences in diet quality in an older Dutch population. Further research is needed to investigate which other factors may explain SEP differences in diet quality.

Reducing cardiometabolic risk in adults with a low socioeconomic position: protocol of the Supreme Nudge parallel cluster-randomised controlled supermarket trial.

BACKGROUND: Unhealthy lifestyle behaviours such as unhealthy dietary intake and insufficient physical activity (PA) tend to cluster in adults with a low socioeconomic position (SEP), putting them at high cardiometabolic disease risk. Educational approaches aiming to improve lifestyle behaviours show limited effect in this population. Using environmental and context-specific interventions may create opportunities for sustainable behaviour change. In this study protocol, we describe the design of a real-life supermarket trial combining nudging, pricing and a mobile PA app with the aim to improve lifestyle behaviours and lower cardiometabolic disease risk in adults with a low SEP. METHODS: The Supreme Nudge trial includes nudging and pricing strategies cluster-randomised on the supermarket level, with: i) control group receiving no intervention; ii) group 1 receiving healthy food nudges (e.g., product placement or promotion); iii) group 2 receiving nudges and pricing strategies (taxing of unhealthy foods and subsidizing healthy foods). In collaboration with a Dutch supermarket chain we will select nine stores located in low SEP neighbourhoods, with the nearest competitor store at > 1 km distance and managed by a committed store manager. Across the clusters, a personalized mobile coaching app targeting walking behaviour will be randomised at the individual level, with: i) control group; ii) a group receiving the mobile PA app. All participants (target n = 1485) should be Dutch-speaking, aged 45-75 years with a low SEP and purchase more than half of their household grocery shopping at the selected supermarkets. Participants will be recruited via advertisements and mail-invitations followed by community-outreach methods. Primary outcomes are changes in systolic blood pressure, LDL-cholesterol, HbA1c and dietary intake after 12 months follow-up. Secondary outcomes are changes in diastolic blood pressure, blood lipid markers, waist circumference, steps per day, and behavioural factors including healthy food purchasing, food decision style, social cognitive factors related to nudges and to walking behaviours and customer satisfaction after 12 months follow-up. The trial will be reflexively monitored to support current and future implementation. DISCUSSION: The findings can guide future research and public health policies on reducing lifestyle-related health inequalities, and contribute to a supermarket-based health promotion intervention implementation roadmap. TRIAL REGISTRATION: Dutch Trial Register ID NL7064, 30th of May, 2018.

The association between population density and blood lipid levels in Dutch blood donors.

BACKGROUND: In low and middle-income countries (LMIC), the total and LDL cholesterol and triglyceride levels of residents of urban areas are reported to be higher than those of rural areas. This may be due to differences in lifestyle behaviors between residents of urban areas and rural areas in LMIC. In this study, our aims were to (1) examine whether or not LDL cholesterol, total/HDL ratios and triglyceride levels of individuals in densely populated areas are higher than those of individuals living in less-densely populated areas in a high-income country (HIC) and (2) investigate the potential mediating roles of physical activity and sedentary behavior. METHODS: We used cross-sectional data from 2547 Dutch blood donors that participated in Donor InSight-III. Linear regression was used to analyze the association between population density and LDL cholesterol, total/HDL cholesterol ratio and HDL cholesterol. The mediating roles of moderate-to-vigorous physical activity (MVPA) and sedentary behavior were investigated in a subsample (n = 740) for which objectively measured MVPA/sedentary behavior data was available. Multiple mediation with linear regression analyses were performed and the product-of-coefficients method was used to calculate direct and indirect effects. RESULTS: Mean LDL cholesterol and median total cholesterol/HDL cholesterol ratio and triglyceride levels were 2.89, 3.43 and 1.29 mmol/L, respectively. Population density was not associated with LDL cholesterol [ß 0.00 (- 0.01; 0.01)], log transformed total/HDL cholesterol ratio [ß 1.00 (1.00; 1.00)] and triglyceride levels [ß 1.00 (0.99; 1.00)]. No statistically significant direct or indirect effects were found. CONCLUSION: Contrary to previous findings in LMIC, no evidence was found that population density is associated with blood lipid levels in blood donors in the Netherlands or that MVPA and sedentary behavior mediate this association. This may be the result of socioeconomic differences and, in part, may be due to the good health of the study population and the relatively high population density in the Netherlands. Also, compared to LMIC, differences in physical activity levels in more versus less populated areas may be less pronounced in HIC.

Associations of takeaway outlets with takeaway food consumption and adiposity: longitudinal analysis of the Fenland cohort.

OBJECTIVE: This study builds on prior findings that link increased availability of takeaway food outlets in home, workplace, and commuting environments to greater takeaway consumption and adiposity. Using longitudinal data, we examine associations of takeaway availability at baseline with changes in consumption and adiposity between baseline and follow-up. METHODS: We analyzed data from the Fenland Study, with baseline data from 2005 to 2015 and follow-up from 2015 to 2020. Takeaway outlet availability within 1 mile of participants' home and workplace addresses, based on 2011 local authority data, was assessed. Outcomes included takeaway food consumption (from a food frequency questionnaire) and body fat percentage (measured via dual-energy x-ray absorptiometry) at follow-up. RESULTS: Among 7581 participants (mean [SD] age, 49.3 [7.4] years) with a mean follow-up of 6.7 years, no positive association was found between takeaway outlet availability at baseline and changes in consumption or body fat percentage. However, among the 12 associations tested, the highest combined home-workplace availability of takeaway outlets, compared with none, was associated with a 0.68 decrease in body fat percentage (95% CI: 0.24-1.12). CONCLUSIONS: Although takeaway outlet availability was linked to greater consumption and adiposity at baseline, it did not predict changes over time, underscoring the complexity of dietary behaviors and their relationship with the neighborhood food environment.

Who uses what food retailers? A cluster analysis of food retail usage in the Netherlands.

The aim of this study is to describe how individuals use different food retailers and how food retail usage varies according to socio-demographic and diet-related characteristics. A cross-sectional survey among Dutch adults (N = 1784) was used. Results from the Two-step cluster analysis indicated that there were five clusters of food retail users. Use of discount supermarkets, organic supermarkets, fast-food outlets, and restaurants contributed to clustering, but use of regular supermarkets, local food shops and whether food retailers were close to home or further from home did not. The clusters included mixed food outlet users, discount supermarket and restaurant users, fast-food and restaurant users, predominant discount supermarket users and supermarkets, fast-food and restaurant users. Participants in each cluster had their own characteristics especially in terms of socio-economic position and diet quality. Future studies need to consider further how food retail selection links physical exposure to the food environment and diet.

Socioeconomic distribution of food outlet availability through online food delivery services in seven European countries: A cross-sectional study.

This area-level cross-sectional study examined online food outlet availability through the most popular online food delivery service platforms (OFDS) across seven European countries, and explored how this online food outlet availability was socioeconomically distributed. Data collection of online food outlet availability was automated in England, Italy, Luxembourg, the Netherlands, Portugal, Spain and Switzerland. We used a geographic information system to join online food outlet availability to socio-demographic information. Median number of food outlets delivering through OFDS was highest in England and lowest in Italy, Portugal and Spain. We also found that high-income areas have the greatest online food outlet availability in most countries. In England, areas with a middle income had the least online food outlets available and no income data was available for Switzerland. Further work is needed to understand drivers of disparities in online food outlet availability, as well as possible implications for public health.

The role of material and psychosocial resources in explaining socioeconomic inequalities in diet: A structural equation modelling approach.

We examined whether material and psychosocial resources may explain socioeconomic differences in diet quality. Cross-sectional survey data from 1461 Dutch adults (42.5 (SD 13.7) years on average and 64% female) on socio-demographics, diet quality, psychosocial factors and perceptions of and objective healthiness of the food environment were used in a structural equation model to examine mediating pathways. Indicators for socioeconomic position (SEP) were income, educational, and occupational level and the 2015 Dutch Healthy Diet (DHD15) index assessed diet quality. Material resources included food expenditure, perceptions of healthy food accessibility and healthfulness of the food retail environment. Psychosocial resources were cooking skills, resilience to unhealthy food environments, insensitivity to food cues and healthy eating habits. Higher SEP was associated with better diet quality; Beducation 8.5 (95%CI 6.7; 10.3), Bincome 5.8 (95%CI 3.7; 7.8) and Boccupation 7.5 (95%CI 5.5; 9.4). Material resources did not mediate the association between SEP and diet quality and neither did the psychosocial resources insensitivity to food cues and eating habits. Cooking skills mediated between 13.3% and 19.0% and resilience to unhealthy food environments mediated between 5.9% and 8.6% of the relation between SEP and the DHD15-index. Individual-level factors such as cooking skills can only explain a small proportion of the SEP differences in diet quality. On top of other psychosocial and material resources not included in this study, it is likely that structural factors outside the individual, such as financial, work and living circumstances also play an important role.

The cost of healthy versus current diets in the Netherlands for households with a low, middle and high education.

The cost of food is an important driver of food choice and most evidence suggests that healthier diets are more costly than less healthy diets. However, current attempts to model the cost of healthy and current diets do not take into account the variation in diets or food prices. We calculated the differential cost between healthy and current diets for households with a low, medium and high education in the Netherlands using the DIETCOST program. The DIETCOST program accounts for variations in dietary patterns and allows for the calculation of the distribution of the cost of bi-weekly healthy and current household diets. Data from the Dutch National Food Consumption Survey 2012-2016 was used to construct commonly consumed food lists for the population as a whole and for households with a low, medium and high education and linked to a local food price database. The average cost of current household diets was €211/fortnight (SD 8.9) and the healthy household diet was on average €50 (24%) more expensive. For households with a low, medium and high education, healthy diets were on average 10% (€17), 26% (€50) and 36% (€72) more expensive compared to current diets, respectively. All healthy diets could be classified as affordable (i.e. requiring less than 30% of the average disposable income) as diets required around 20% of the income. To conclude, while healthy diets were found to be affordable, we found that these were more expensive than current diets, especially for those with a higher educational level. This suggests that individuals will need to spend more money on food if they aim to adhere to dietary guidelines under the assumption that they will minimally adjust their diet. Bridging the gap between the cost of healthy and less healthy foods could be an important strategy for improving population diets.

Shifting toward a healthier dietary pattern through nudging and pricing strategies: A secondary analysis of a randomized virtual supermarket experiment.

BACKGROUND: Nudging and salient pricing are promising strategies to promote healthy food purchases, but it is possible their effects differ across food groups. OBJECTIVE: To investigate in which food groups nudging and/or pricing strategies most effectively changed product purchases and resulted in within-food groups substitutions or spillover effects. METHODS: In total, 318 participants successfully completed a web-based virtual supermarket experiment in the Netherlands. We conducted a secondary analysis of a mixed randomized experiment consisting of 5 conditions (within subject) and 3 arms (between subject) to investigate the single and combined effects of nudging (e.g., making healthy products salient), taxes (25% price increase), and/or subsidies (25% price decrease) across food groups (fruit and vegetables, grains, dairy, protein products, fats, beverages, snacks, and other foods). Generalized linear mixed models were used to estimate the incidence rate ratios and 95% CIs for changes in the number of products purchased. RESULTS: Compared with the control condition, the combination of subsidies on healthy products and taxes on unhealthy products in the nudging and price salience condition was overall the most effective, as the number of healthy purchases from fruit and vegetables increased by 9% [incidence rate ratio (IRR) = 1.09; 95% CI: 1.02, 1.18], grains by 16% (IRR = 1.16; 95% CI: 1.05, 1.28), and dairy by 58% (IRR = 1.58; 95% CI: 1.31, 1.89), whereas the protein and beverage purchases did not significantly change. Regarding unhealthy purchases, grains decreased by 39% (IRR = 0.72; 95% CI: 0.63, 0.82) and dairy by 30% (IRR = 0.77; 95% CI: 0.68, 0.87), whereas beverage and snack purchases did not significantly change. The groups of grains and dairy showed within-food group substitution patterns toward healthier products. Beneficial spillover effects to minimally targeted food groups were seen for unhealthy proteins (IRR = 0.81; 95% CI: 0.73, 0.91). CONCLUSIONS: Nudging and salient pricing strategies have a differential effect on purchases of a variety of food groups. The largest effects were found for dairy and grains, which may therefore be the most promising food groups to target in order to achieve healthier purchases. The randomized trial on which the current secondary analyses were based is registered in the Dutch trial registry (NTR7293; www.trialregister.nl).

Recruitment of Participants for a 3D Virtual Supermarket: Cross-sectional Observational Study.

BACKGROUND: Virtual supermarkets offer a practical and affordable setting to test the efficacy of different pricing and nudging strategies before they are implemented in the real world. Despite the advantages of using virtual supermarkets for this purpose, conducting studies in online settings is challenging with regard to recruitment and retention of sufficient and suitable participants. OBJECTIVE: To describe cost, time, and retention with regard to participants recruited using various strategies and potential sociodemographic differences between participants recruited via different strategies. METHODS: This cross-sectional study used data from a randomized controlled trial in which 455 Dutch adults with low and high educational levels were invited to shop 5 times in a 3D virtual supermarket. Participants were recruited via social media and flyers. A log that tracked the costs of and time spent on the different recruitment strategies was kept by the study team. Outcome measures included the cost of recruitment strategies, the time investment by researchers, and recruitment and attrition rates of participants in the study. RESULTS: The median age of study completers was 31.0 (IQR 25.0) and 157 out of 346 study completers (45.4%) were highly educated. Out of the 455 included participants, 235 (51.6%) were recruited via social media campaigns, 131 (28.8%) via home-delivered flyers, 38 (8.4%) via flyers directly distributed by the study team, and 46 (10.1%) via word-of-mouth. Of all paid recruitment strategies, social media campaigns were the cheapest and least time-consuming, whereas the distribution of flyers by the study team was the most expensive and time-consuming recruitment strategy. Age, sex, overweight status, employment situation, and number of adults within the household varied by recruitment strategy. CONCLUSIONS: Using different recruitment strategies resulted in the efficient recruitment of a representative study sample and retention of participants was relatively high. While "word-of-mouth" was the most cost- and time-effective recruitment strategy, using only one type of recruitment strategy could result in a demographically skewed study population.

Body size ideals and body satisfaction among Dutch-origin and African-origin residents of Amsterdam: The HELIUS study.

OBJECTIVE: Obesity is highly prevalent among ethnic minorities and acceptance of larger body sizes may put these ethnic minorities at risk of obesity. This study aimed to examine body size ideals and body satisfaction in relation to body weight, in two Sub-Saharan African (SSA)-origin groups in the Netherlands compared to the Dutch. Additionally, in the two SSA-origin groups, this study assessed the mediating role of acculturation in the relation between ethnicity and body size ideals and body satisfaction. METHODS: Dutch, African Surinamese and Ghanaians living in Amsterdam, the Netherlands, participated in the observational HELIUS study (n = 10,854). Body size ideals were assessed using a validated nine figure scale. Body satisfaction was calculated as the concordance of current with ideal figure. Acculturation was only assessed among SSA-origin participants and acculturation proxies included age of migration, residence duration, ethnic identity and social network. Weight and height were measured using standardised protocols. RESULTS: SSA-origin women and Ghanaian men had larger body size ideals compared to the Dutch; e.g. Surinamese and Ghanaian women had 0.37 (95%CI 0.32; 0.43) and 0.70 (95%CI 0.63; 0.78) larger body size ideals compared to Dutch women. SSA-origin participants were more often satisfied with their weight compared to the Dutch. Similarly, SSA-origin participants had more than twice the odds of being satisfied/preferring a larger figure compared to the Dutch (e.g. BSurinamese men 2.44, 95%CI 1.99; 2.99). Within the two SSA-origin groups, most acculturation proxies mediated the relation between ethnicity and body size ideals in women. Limited evidence of mediation was found for the outcome body satisfaction. CONCLUSION: Public health strategies promoting a healthy weight may need to be differentiated according to sex and ethnic differences in body weight perception. Factors other than acculturation may underlie the ethnic differences between African Surinamese and Ghanaians in obesity.

The Moderating Role of Social Neighbourhood Factors in the Association between Features of the Physical Neighbourhood Environment and Weight Status.

BACKGROUND: This paper investigated the independent and joint associations between aspects of the physical neighbourhood environment and social neighbourhood factors with BMI and overweight status in European adults. METHODS: Data from 5,199 participants in the SPOTLIGHT survey were analysed. Participants reported on their height, weight and perceptions of the neighbourhood. Objectively measured aspects of the physical neighbourhood environment included: presence of recreational facilities, features of the active transportation environment, neighbourhood aesthetics and presence of different types of food outlets. Social factors included the self-reported variables social network, social cohesion, social trust and perceived crime and the census variable neighbourhood socioeconomic status. Outcome measures were BMI and overweight status. Main associations between physical and social factors and BMI/overweight status were analysed using multilevel regression analyses adjusted for confounders. Moderation analysis was conducted by adding the interaction terms between physical and social neighbourhood factors one by one to the multivariable models. Significant interaction terms were then stratified. RESULTS: Significant associations with BMI/overweight status were found for features of the active transportation environment and all social factors, except perceived crime. Several significant interaction terms were detected, but no significant associations between the physical neighbourhood environment and BMI/overweight status were found after stratification. CONCLUSION: We did not find consistent interactions between physical and social neighbourhood factors to explain BMI and overweight status.