Impulsivity in the supermarket. Responses to calorie taxes and subsidies in healthy weight undergraduates

The relationship between inhibitory control and food consumption or choice: A systematic review and meta-analysis

Excess consumption of unhealthy foods has become a major public health problem. Although one potential contributor to unhealthy consumption is poor inhibitory control, findings have been inconsistent. A meta-analysis of 35 studies was conducted to determine whether, and under which conditions, inhibitory control, as measured by the Go/No-Go and Stop-Signal tasks, is associated with food consumption/choice. Moderators included the type of stimuli (neutral or food-specific) used in measuring inhibitory control, sample differences (e.g., age, gender, and weight), and the measure of food consumption or choice. Overall, there was a small positive association between inhibitory control and food consumption/choice, r = .09, CI₉₅ = [0.04, 0.14], p = .001. This held for the Stop-Signal Task in general, and for the Go/No-Go Task for children and when food consumption/choice was measured objectively. The present meta-analysis provides the first comprehensive evidence that inhibitory control, as measured by the Go/No-Go and Stop-Signal tasks, is associated with food consumption or choice, and points to inhibitory control as a potential target for reducing unhealthy food consumption.

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.

Obesity under full fresh fruit and vegetable access conditions

There is no agreement regarding the role of fresh fruit and vegetables' affordability, accessibility and availability, or access in general, on obesity rates. In this article we investigated whether access to fresh fruit and vegetables is related to better biometric indicators such as weight and body mass index. Using mediation and matching methods and assuming that farmers and traditional market sellers have easy access to fruit and vegetables, we found that having better access is not associated to a reduction in weight or body mass index. Potential explanations for this result are that better access was not associated with fresh fruit and vegetables' consumption and fruit and vegetables' consumption was not associated with weight and body mass index. Also, fresh fruit and vegetables' sellers had a higher weight and body mass index compared to the rest of the population but, a similar weight and body mass index compared to people with their same educational level. Therefore, variations on weight and body mass index were more associated with educational level rather than with access. Access may not be the single story to explain fruit and vegetable consumption.

Retail Nutrition Programs and Outcomes: An Evidence Analysis Center Scoping Review

As nutrition-related diseases contribute to rising health care costs, food retail settings are providing a unique opportunity for registered dietitian nutritionists (RDNs) to address the nutritional needs of consumers. Food as Medicine interventions play a role in preventing and/or managing many chronic conditions that drive health care costs. The objective of this scoping review was to identify and characterize literature examining Food as Medicine interventions within food retail settings and across consumer demographics. An electronic literature search of 8 databases identified 11,404 relevant articles. Results from the searches were screened against inclusion criteria, and intervention effectiveness was assessed for the following outcomes: improvement in health outcomes and cost-effectiveness. One-hundred and eighty-six papers and 25 systematic reviews met inclusion criteria. Five categories surfaced as single interventions: prescription programs, incentive programs, medically tailored nutrition, path-to-purchase marketing, and personalized nutrition education. Multiple combinations of intervention categories, reporting of health outcomes (nutritional quality of shopping purchases, eating habits, biometric measures), and cost-effectiveness (store sales, health care dollar savings) also emerged. The intervention categories that produced both improved health outcomes and cost-effectiveness included a combination of incentive programs, personalized nutrition education, and path-to-purchase marketing. Food as Medicine interventions in the food retail setting can aid consumers in navigating health through diet and nutrition by encompassing the following strategic focus areas: promotion of health and well-being, managing chronic disease, and improving food security. Food retailers should consider the target population and desired focus areas and should engage registered dietitian nutritionists when developing Food as Medicine interventions.

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 ).

Does self-control modify the impact of interventions to change alcohol, tobacco, and food consumption? A systematic review

Low self-control is associated with increased consumption of alcohol, tobacco, and unhealthy food. This systematic review aimed to assess whether individual differences in self-control modify the effectiveness of interventions to reduce consumption of these products, and hence their potential to reduce consumption amongst those whose consumption is generally greater. Searches of six databases were supplemented with snowball searches and forward citation tracking. Narrative synthesis summarised findings by: consumption behaviour (alcohol, tobacco, food); psychological processes targeted by the intervention (reflective, non-reflective, or both); and study design (experiment, cohort, or cross-sectional). Of 54 eligible studies, 22 reported no evidence of modification, 18 reported interventions to be less effective in those with low self-control, and 14 reported interventions to be more effective in those with low self-control. This pattern did not differ from chance. Whilst self-control often influenced intervention outcomes, there was no consistent pattern of effects, even when stratifying studies by consumption behaviour, intervention type, or study design. There was a notable absence of evidence regarding interventions that restructure physical or economic environments. In summary, a heterogeneous, low-quality evidence base suggests an inconsistent moderating effect of low self-control on the effectiveness of interventions to change consumption behaviours.

The Relative Costs of High- vs. Low-Energy-Density Foods and More vs. Less Healthful Beverages Consumed by Children

OBJECTIVE

To compare grocery costs between relatively high energy density foods and sugar-sweetened/high-fat beverages and lower energy density foods and more healthful beverages in children's diets.

METHODS

Sixty foods were divided into high and low energy density baskets. Fourteen beverages were designated to either basket based on fat and added-sugar content. Prices were collected at 60 grocery stores and composite costs compared between baskets using Wilcoxon tests.

RESULTS

The cost per kilogram of high energy density foods was greater, but the cost per quart of sugar-sweetened/high-fat beverages was lower than more healthful beverages. The cost per 1000 calories and the cost per serving of the high energy density basket were lower.

CONCLUSIONS

The relative cost of high and low energy density foods in children's diets depends on how cost is quantified. "Pound-for-pound," lower energy density foods and more healthful beverages are generally less expensive, but high energy density foods and less healthful beverages are cheaper per serving. Cost metrics including other factors (e.g. time cost) may further clarify the role of grocery prices in children's diets.

Using a UK Virtual Supermarket to Examine Purchasing Behavior Across Different Income Groups in the United Kingdom: Development and Feasibility Study

BACKGROUND

The majority of food in the United Kingdom is purchased in supermarkets, and therefore, supermarket interventions provide an opportunity to improve diets. Randomized controlled trials are costly, time-consuming, and difficult to conduct in real stores. Alternative approaches of assessing the impact of supermarket interventions on food purchases are needed, especially with respect to assessing differential impacts on population subgroups.

OBJECTIVE

The aim of this study was to assess the feasibility of using the United Kingdom Virtual Supermarket (UKVS), a three-dimensional (3D) computer simulation of a supermarket, to measure food purchasing behavior across income groups.

METHODS

Participants (primary household shoppers in the United Kingdom with computer access) were asked to conduct two shopping tasks using the UKVS and complete questionnaires on demographics, food purchasing habits, and feedback on the UKVS software. Data on recruitment method and rate, completion of study procedure, purchases, and feedback on usability were collected to inform future trial protocols.

RESULTS

A total of 98 participants were recruited, and 46 (47%) fully completed the study procedure. Low-income participants were less likely to complete the study (P=.02). Most participants found the UKVS easy to use (38/46, 83%) and reported that UKVS purchases resembled their usual purchases (41/46, 89%).

CONCLUSIONS

The UKVS is likely to be a useful tool to examine the effects of nutrition interventions using randomized controlled designs. Feedback was positive from participants who completed the study and did not differ by income group. However, retention was low and needs to be addressed in future studies. This study provides purchasing data to establish sample size requirements for full trials using the UKVS.

Impact of sugars and sugar taxation on body weight control: A comprehensive literature review

OBJECTIVE

To conduct a comprehensive literature review in the field of added-sugar consumption on weight gain including the effect of fructose-containing caloric sweeteners and sugar taxation.

METHODS

A search of three databases was conducted in the time period from the inception of the databases to August 2015. Sensitive search strategies were used in order to retrieve systematic reviews (SR) of fructose, sucrose, or sugar-sweetened beverages (SSBs) on weight gain and metabolic adverse effects, conducted on humans and written in English, Spanish, or French. In addition, a review about SSB taxation and weight outcomes was conducted.

RESULTS

The search yielded 24 SRs about SSBs and obesity, 23 SRs on fructose or SSBs and metabolic adverse effects, and 24 studies about SSB taxation and weight control.

CONCLUSIONS

The majority of SRs, especially the most recent ones, with the highest quality and without any disclosed conflict of interest, suggested that the consumption of SSBs is a risk factor for obesity. The effect of fructose-containing caloric sweeteners, on weight gain is mediated by overconsumption of beverages with these sweeteners, leading to an extra provision of energy intake. The tax tool alone on added sugars appears insufficient to curb the obesity epidemic, but it needs to be included in a multicomponent structural strategy.

A process evaluation of the Supermarket Healthy Eating for Life (SHELf) randomized controlled trial

Background

Supermarket Healthy Eating for Life (SHELf) was a randomized controlled trial that operationalized a socioecological approach to population-level dietary behaviour change in a real-world supermarket setting. SHELf tested the impact of individual (skill-building), environmental (20 % price reductions), and combined (skill-building + 20 % price reductions) interventions on women’s purchasing and consumption of fruits, vegetables, low-calorie carbonated beverages and water. This process evaluation investigated the reach, effectiveness, implementation, and maintenance of the SHELf interventions.

Methods

RE-AIM provided a conceptual framework to examine the processes underlying the impact of the interventions using data from participant surveys and objective sales data collected at baseline, post-intervention (3 months) and 6-months post-intervention. Fisher’s exact, χ² and t-tests assessed differences in quantitative survey responses among groups. Adjusted linear regression examined the impact of self-reported intervention dose on food purchasing and consumption outcomes. Thematic analysis identified key themes within qualitative survey responses.

Results

Reach of the SHELf interventions to disadvantaged groups, and beyond study participants themselves, was moderate. Just over one-third of intervention participants indicated that the interventions were effective in changing the way they bought, cooked or consumed food (p < 0.001 compared to control), with no differences among intervention groups. Improvements in purchasing and consumption outcomes were greatest among those who received a higher intervention dose. Most notably, participants who said they accessed price reductions on fruits and vegetables purchased (519 g/week) and consumed (0.5 servings/day) more vegetables. The majority of participants said they accessed (82 %) and appreciated discounts on fruits and vegetables, while there was limited use (40 %) and appreciation of discounts on low-calorie carbonated beverages and water. Overall reported satisfaction with, use, and impact of the skill-building resources was moderate. Maintenance of newly acquired behaviours was limited, with less than half of participants making changes or using study-provided resources during the 6-month post-intervention period.

Conclusions

SHELf’s reach and perceived effectiveness were moderate. The interventions were more effective among those reporting greater engagement with them (an implementation-related construct). Maintenance of newly acquired behaviours proved challenging.

Trial registration

Current controlled trials ISRCTN39432901.

A systematic review of the relationship between eating, weight and inhibitory control using the stop signal task

Altered inhibitory control (response inhibition, reward-based inhibition, cognitive inhibition, reversal learning) has been implicated in eating disorders (EDs) and obesity. It is unclear, however, how different types of inhibitory control contribute to eating and weight-control behaviours. This review evaluates the relationship between one aspect of inhibitory control (a reactive component of motor response inhibition measured by the stop signal task) and eating/weight in clinical and non-clinical populations. Sixty-two studies from 58 journal articles were included. Restrained eaters had diminished reactive inhibitory control compared to unrestrained eaters, and showed greatest benefit to their eating behaviour from manipulations of inhibitory control. Obese individuals may show less reactive inhibitory control but only in the context of food-specific inhibition or after executive resources are depleted. Of the limited studies in EDs, the majority found no impairment in reactive inhibitory control, although findings are inconsistent. Thus, altered reactive inhibitory control is related to some maladaptive eating behaviours, and hence may provide a therapeutic target for behavioural manipulations and/or neuromodulation. However, other types of inhibitory control may also contribute. Methodological and theoretical considerations are discussed.

Effects of nutrient profiling and price changes based on NuVal® scores on food purchasing in an online experimental supermarket

OBJECTIVE

The goal of the present study was to apply experimental economic methods in an online supermarket to examine the effects of nutrient profiling, and differential pricing based on the nutrient profile, on the overall diet quality, energy and macronutrients of the foods purchased, and diet cost.

DESIGN

Participants were provided nutrient profiling scores or price adjustments based on nutrient profile scores while completing a hypothetical grocery shopping task. Prices of foods in the top 20 % of nutrient profiling scores were reduced (subsidized) by 25 % while those in the bottom 20 % of scores were increased (taxed) by 25 %. We evaluated the independent and interactive effects of nutrient profiling or price adjustments on overall diet quality of foods purchased as assessed by the NuVal® score, energy and macronutrients purchased and diet cost in a 2×2 factorial design.

SETTING

A large (>10 000 food items) online experimental supermarket in the USA.

SUBJECTS

Seven hundred and eighty-one women.

RESULTS

Providing nutrient profiling scores improved overall diet quality of foods purchased. Price changes were associated with an increase in protein purchased, an increase in energy cost, and reduced carbohydrate and protein costs. Price changes and nutrient profiling combined were associated with no unique benefits beyond price changes or nutrient profiling alone.

CONCLUSIONS

Providing nutrient profile score increased overall NuVal® score without a reduction in energy purchased. Combining nutrient profiling and price changes did not show an overall benefit to diet quality and may be less useful than nutrient profiling alone to consumers who want to increase overall diet quality of foods purchased.

Consumer Acceptance of Population-Level Intervention Strategies for Healthy Food Choices: The Role of Perceived Effectiveness and Perceived Fairness

The present study investigates acceptance of intervention strategies for low-calorie snack choices that vary regarding the effect they have on consumers’ freedom of choice (providing information, guiding choice through (dis)incentives, and restricting choice). We examine the mediating effects of perceived effectiveness and perceived fairness, and the moderating effects of barriers to choose low-calorie snacks and perceived responsibility for food choice. Data was collected through an online survey, involving three waves that were completed over a seven week timespan. Information was collected on barriers and perceived responsibility, and evaluations of a total of 128 intervention strategies with varying levels of intrusiveness that were further systematically varied in terms of source, location, approach/avoidance, type, and severity. A total of 1173 respondents completed all three waves. We found that the effect of intervention intrusiveness on acceptance was mediated by the perceived personal- and societal effectiveness, and the perceived fairness of interventions. For barriers and perceived responsibility, only main effects on intervention-specific beliefs were found. Government interventions were accepted less than interventions by food manufacturers. In conclusion, the present study shows that acceptance of interventions depends on perceptions of personal- and societal effectiveness and fairness, thereby providing novel starting points for increasing acceptance of both existing and new food choice interventions.

Heterogeneity in barriers regarding the motivation, the opportunity and the ability to choose low-calorie snack foods and beverages: associations with real-life choices

Objective

Employing Rothschild’s Motivation–Opportunity–Ability framework, the present study examines the extent to which heterogeneity in barriers regarding the motivation, the perceived opportunity and the perceived ability to choose low-calorie over high-calorie snacks is associated with the proportion of low-calorie snack choices in real life. Furthermore, the study investigates which dominant barrier profiles can be discerned.

Design

Data were obtained from a survey about participants’ motivation, opportunity and ability to choose low-calorie over high-calorie snacks and an FFQ that measured habitual consumption of snack foods and beverages. Data were analysed using R packages lavaan and NbClust, and IBM SPSS Statistics.

Setting

A representative sample (n 1318) of the Dutch population based on gender (686 women), age and education level.

Results

For both snack foods and beverages, motivation to choose low-calorie over high-calorie snacks was associated strongest with proportions of low-calorie choices. The perceived ability and perceived opportunity were also associated with proportions of low-calorie choices, albeit to a lesser extent. Furthermore, three dominant profiles of barriers were identified: the no-barrier profile, the lack-of-opportunity profile and the lack-of-motivation profile. These profiles differed significantly on proportions of low-calorie snack choices, daily meal consumption and sociodemographic characteristics.

Conclusions

Heterogeneity in barriers regarding the motivation, the perceived opportunity and the perceived ability to choose low-calorie over high-calorie snacks is associated with the proportion of low-calorie snack choices in real life. By identifying and appreciating heterogeneity in barriers, the present study provides further incentives for the tailoring of intervention strategies.

Differential Responses to Food Price Changes by Personal Characteristic: A Systematic Review of Experimental Studies

BACKGROUND

Fiscal interventions to improve population diet have been recommended for consideration by many organisations including the World Health Organisation and the United Nations and policies such as sugar-sweetened beverage taxes have been implemented at national and sub-national levels. However, concerns have been raised with respect to the differential impact of fiscal interventions on population sub-groups and this remains a barrier to implementation.

OBJECTIVE

To examine how personal characteristics (such as socioeconomic status, sex, impulsivity, and income) moderate changes in purchases of targeted foods in response to food and beverage price changes in experimental settings.

DESIGN

Systematic review.

DATA SOURCES

Online databases (PubMed, EMBASE, Web of Science, EconLit and PsycInfo), reference lists of previous reviews, and additional data from study authors.

STUDY SELECTION

We included randomised controlled trials where food and beverage prices were manipulated and reported differential effects of the intervention on participant sub-groups defined according to personal characteristics.

DATA ANALYSIS

Where possible, we extracted data to enable the calculation of price elasticities for the target foods by personal characteristic.

RESULTS

8 studies were included in the review. Across studies, the difference in price elasticity varied from 0.02 to 2.43 between groups within the same study. 11 out of the total of 18 comparisons of own-price elasticity estimates by personal characteristic differed by more than 0.2 between groups. Income related factors were the most commonly considered and there was an indication that own-price elasticity estimates do vary by income but the direction of this effect was not clear.

CONCLUSION

Experimental studies provide an opportunity to examine the differential effects of fiscal measures to improve population diets. Patterns in price sensitivity by personal characteristics are complex. General conclusions pertaining to the effects of personal characteristics on price sensitivity are not supported by the evidence, which shows heterogeneity between studies and populations.

TRIAL REGISTRATION

PROSPERO CRD42014009705.

Experimental analysis of the effect of taxes and subsides on calories purchased in an on-line supermarket

Taxes and subsidies are a public health approach to improving nutrient quality of food purchases. While taxes or subsidies influence purchasing, it is unclear whether they influence total energy or overall diet quality of foods purchased. Using a within subjects design, selected low nutrient dense foods (e.g. sweetened beverages, candy, salty snacks) were taxed, and fruits and vegetables and bottled water were subsidized by 12.5% or 25% in comparison to a usual price condition for 199 female shoppers in an experimental store. Results showed taxes reduced calories purchased of taxed foods (coefficient = -6.61, CI = -11.94 to -1.28) and subsidies increased calories purchased of subsidized foods (coefficient = 13.74, CI = 8.51 to 18.97). However, no overall effect was observed on total calories purchased. Both taxes and subsidies were associated with a reduction in calories purchased for grains (taxes: coefficient = -6.58, CI = -11.91 to -1.24, subsidies: coefficient = -12.86, CI = -18.08 to -7.63) and subsidies were associated with a reduction in calories purchased for miscellaneous foods (coefficient = -7.40, CI = -12.62 to -2.17) (mostly fats, oils and sugars). Subsidies improved the nutrient quality of foods purchased (coefficient = 0.14, CI = 0.07 to 0.21). These results suggest that taxes and subsidies can influence energy purchased for products taxed or subsidized, but not total energy purchased. However, the improvement in nutrient quality with subsidies indicates that pricing can shift nutritional quality of foods purchased. Research is needed to evaluate if differential pricing strategies based on nutrient quality are associated with reduction in calories and improvement in nutrient quality of foods purchased.

Offering within-category food swaps to reduce energy density of food purchases: a study using an experimental online supermarket

Background

Swaps are often used to encourage healthier food choices, but there is little evidence of their effectiveness. The current study assessed the impact of offering swaps on groceries purchased within a bespoke online supermarket; specifically the objective was to measure the impact on energy density (ED) of food purchases following the offer of lower ED alternatives (a) at point of selection or at checkout, and (b) with or without explicit consent to receive swap prompts.

Method

Participants were asked to complete a 12-item shopping task within an online shopping platform, developed for studying food purchasing. 1610 adults were randomly assigned to a no swap control condition or to one of four interventions: consented swaps at selection; consented swaps at checkout; imposed swaps at selection; or imposed swaps at checkout. Each swap presented two lower ED options from the same category as the participant’s chosen food. Swap acceptance rate and purchased food ED were the primary outcomes.

Results

Of the mean 12.36 (SD 1.26) foods purchased, intervention participants were offered a mean of 4.1 (SD 1.68) swaps, with the potential to reduce the ED of purchased food (effect (95 % CI): −83 kJ/100 g (−110 – -56), p = <0.0001). A median of one swap (IQR 0 to 2) was accepted, not significantly reducing the purchased food ED (effect (95 % CI): −24 kJ/100 g (4 – -52), p = 0.094). More swaps were accepted when offered at selection than at checkout (OR (95 % CI) = 1.224 (1.11 – 1.35), p < 0.0001), but no differences were seen with consent. Purchased food ED was unaffected by point of swap or consent, but reduced with number of swaps accepted (effect per swap (95 % CI) = −24 kJ/100 g (−35 – -14), p < 0.0001).

Conclusion

Within category swaps did not reduce the ED of food purchases reflecting the observation that the use of swaps within an on-line shopping platform offered small potential gains in ED and a minority was accepted.

Electronic supplementary material

The online version of this article (doi:10.1186/s12966-015-0241-1) contains supplementary material, which is available to authorized users.

Understanding consumer acceptance of intervention strategies for healthy food choices: a qualitative study

Background

The increasing prevalence of overweight and obesity poses a major threat to public health. Intervention strategies for healthy food choices potentially reduce obesity rates. Reviews of the effectiveness of interventions, however, show mixed results. To maximise effectiveness, interventions need to be accepted by consumers. The aim of the present study is to explore consumer acceptance of intervention strategies for low-calorie food choices. Beliefs that are associated with consumer acceptance are identified.

Methods

Data was collected in the Netherlands in 8 semi-structured interviews and 4 focus group discussions (N = 39). Nine archetypical strategies representing educational, marketing and legal interventions served as reference points. Verbatim transcriptions were coded both inductively and deductively with the framework approach.

Results

We found that three beliefs are related to consumer acceptance: 1) general beliefs regarding obesity, such as who is responsible for food choice; 2) the perceived effectiveness of interventions; and 3) the perceived fairness of interventions. Furthermore, the different aspects underlying these general and intervention-specific beliefs were identified.

Conclusions

General and intervention-specific beliefs are associated with consumer acceptance of interventions for low-calorie food choices. Policymakers in the food domain can use the findings to negotiate the development of interventions and to assess the feasibility of interventions. With respect to future research, we recommend that segments of consumers based on perceptions of intervention strategies are identified.

Effectiveness of subsidies in promoting healthy food purchases and consumption: a review of field experiments

OBJECTIVE

To systematically review evidence from field interventions on the effectiveness of monetary subsidies in promoting healthier food purchases and consumption.

DESIGN

Keyword and reference searches were conducted in five electronic databases: Cochrane Library, EconLit, MEDLINE, PsycINFO and Web of Science. Studies were included based on the following criteria: (i) intervention: field experiments; (ii) population: adolescents 12–17 years old or adults 18 years and older; (iii) design: randomized controlled trials, cohort studies or pre–post studies; (iv) subsidy: price discounts or vouchers for healthier foods; (v) outcome: food purchases or consumption; (vi) period: 1990–2012; and (vii) language: English. Twenty-four articles on twenty distinct experiments were included with study quality assessed using predefined methodological criteria.

SETTING

Interventions were conducted in seven countries: the USA (n 14), Canada (n 1), France (n 1), Germany (n 1), Netherlands (n 1), South Africa (n 1) and the UK (n 1). Subsidies applied to different types of foods such as fruits, vegetables and low-fat snacks sold in supermarkets, cafeterias, vending machines, farmers’ markets or restaurants.

SUBJECTS

Interventions enrolled various population subgroups such as school/ university students, metropolitan transit workers and low-income women.

RESULTS

All but one study found subsidies on healthier foods to significantly increase the purchase and consumption of promoted products. Study limitations include small and convenience samples, short intervention and follow-up duration, and lack of cost-effectiveness and overall diet assessment.

CONCLUSIONS

Subsidizing healthier foods tends to be effective in modifying dietary behaviour. Future studies should examine its long-term effectiveness and cost-effectiveness at the population level and its impact on overall diet intake.

Experimental research on the relation between food price changes and food-purchasing patterns: a targeted review

One way in which to modify food purchases is to change prices through tax policy, subsidy policy, or both. We reviewed the growing body of experimental research conducted in the laboratory and in the field that investigates the following: the extent to which price changes influence purchases of targeted and nontargeted foods, total energy, or macronutrients purchased; the interaction of price changes with adjunctive interventions; and moderators of sensitivity to price changes. After a brief overview of economic principles and observational research that addresses these issues, we present a targeted review of experimental research. Experimental research suggests that price changes modify purchases of targeted foods, but research on the overall nutritional quality of purchases is mixed because of substitution effects. There is mixed support for combining price changes with adjunctive interventions, and there are no replicated findings on moderators to price sensitivity in experiments. Additional focused research is needed to better inform food policy development with the aim of improving eating behavior and preventing obesity.

The effects of a 25% discount on fruits and vegetables: results of a randomized trial in a three-dimensional web-based supermarket

Background

Lowering the price of fruit and vegetables is a promising strategy in stimulating the purchase of those foods. However, the true effects of this strategy are not well studied and it is unclear how the money saved is spent. The aim of this study is to examine the effects of a 25% discount on fruits and vegetables on food purchases in a supermarket environment.

Methods

A randomized controlled trial with two research conditions was conducted: a control condition with regular prices (n = 52) and an experimental condition with a 25% discount on fruits and vegetables (n = 63). The experiment was carried out using a three-dimensional web-based supermarket, which is a software application in the image of a real supermarket. Data were collected in 2010 in the Netherlands. Participants received a fixed budget and were asked to buy weekly household groceries at the web-based supermarket. Differences in fruit and vegetable purchases, differences in expenditures in other food categories and differences in total calories were analyzed using independent samples t-tests and multiple linear regression models accounting for potential effect modifiers and confounders.

Results

The purchased amount of fruit plus vegetables was significantly higher in the experimental condition compared to the control condition (Δ984 g per household per week, p = .03) after appropriate adjustments. This corresponds to a 25% difference compared to the control group. Both groups had similar expenditures in unhealthier food categories, including desserts, soda, crisps, candy and chocolate. Furthermore, both groups purchased an equal number of food items and an equal amount of calories, indicating that participants in the discount condition did not spend the money they saved from the discounts on other foods than fruits and vegetables.

Conclusion

A 25% discount on fruits and vegetables was effective in stimulating purchases of those products and did neither lead to higher expenditures in unhealthier food categories nor to higher total calories purchased. Future studies in real supermarkets need to confirm these findings.