Assessing the impact of dietary health interventions for driving long-term positive changes in diet and nutrition in Scotland
Project Lead
Challenges
Rising consumer demand for foods high in energy, salt, sugar, fat, and animal protein exacerbates the prevalence of diet-related diseases, which can translate into bigger economic burdens for the health services and the food and drink sector through lost production. Furthermore, there is strong evidence that unhealthy eating plays a key role in driving health inequalities between people living in advantaged and disadvantaged circumstances. Although diet quality in Scotland has improved over recent decades, it still falls well short of international and national guidelines.
Growing evidence suggests that multiple and complex factors beyond personal decisions strongly influence dietary choices and patterns. Individual dietary habits are determined by personal preference, age, gender, culture, education, income, health status, and nutritional awareness. Wider commercial pressures, including food packaging, marketing, advertising, and sociocultural perceptions of norms, status, and prestige, further affect consumer choice. With thoughtful evidence-informed policy, leveraging these factors provides an opportunity for governments to support improvements in diets, wellbeing, and equity.
With rising diet-related diseases globally, including in Scotland, policies such as taxation, subsidies, regulation, food reformulation and labelling are heavily favoured to help align food choices with health and wellbeing. Several dietary interventions, such as fiscal measures, nutrition education, nutritional labelling, advertising control, and social marketing, have been implemented with mixed effectiveness.
In Scotland, evidence of the impact of dietary interventions on food and drink purchases and diet quality remains scarce. More evidence is needed to assess the impact of selected dietary interventions on Scottish consumers’ food and drink purchases, energy intake, and diet quality, while controlling for possible unintended consequences and the diversity of consumers’ choices and purchases.
Questions
- What behaviour change interventions can influence consumers to make long-term changes with respect to their diet and food safety; that reduce or minimise health inequalities?
Solutions
This project is evaluating the impact of dietary health interventions (fiscal measures, nutrition education, nutritional labelling, advertising control, and social marketing) for improving Scotland’s diet and nutrition and investigating whether and how their impact varies over time and across demographic groups.
Impact of dietary interventions on diet quality and wellbeing
We are analysing the evidence on the impact of dietary interventions on diet quality and wellbeing, and the methods used to assess the impact. This involves a literature review where we are identifying key dietary interventions, and their evaluation methods, to persuade consumers in the UK and elsewhere to improve their diet and will summarise their strengths, limitations, risks, and opportunities.
Analysing long-term trends in food and drink purchases
We are evaluating consumer dietary and healthy behaviours by analysing their demand for fruit and drink over time. First, we are creating specific econometric datasets for various analyses. These datasets are used to develop a demand model and to calculate price and income elasticities to explain and predict consumer food and drink purchasing behaviour for the average Scottish household and segmented across demographics (e.g., gender, age, deprivation) over time.
Assessing the impact of dietary interventions
We are selecting interventions relevant to Scotland’s context and analysing their impact on Scottish consumers’ food purchases, calorie intake, and diet quality using time-series and cross-sectional data. We are measuring Scottish consumers’ food and drink purchases and their determining factors and evaluating their trends over time and across demographic groups. We are providing new insights into Scottish consumers’ food and drink purchase patterns and their drivers.
Using market and experimental data, we are performing in-depth analyses to simulate the positive and negative impact of implementing selected dietary interventions on consumer food and drink purchasing behaviour, total calories purchased, and indices of diet quality. This is focusing on measuring the impact of the selected interventions on indices of diet quality, health, inequality, and consumer willingness to pay. We are also evaluating the potential unintended consequences of implementing dietary interventions. Further, we are investigating contextual and individual factors such as retail environment, marketing tools, socio-economic status, gender, age, education, and income, which may impact the effectiveness of dietary interventions. This new evidence and these insights are informing recommendations for dietary interventions likely to improve diet, nutrition, and health equity in Scotland.
Overall, this project contributes to the knowledge of the effectiveness of dietary interventions by assessing the impact of implementing dietary interventions on consumers’ food purchases and the nutritional content of their diet.
Project Partners
Progress
The research team has completed reviewing the literature on the impact of dietary interventions on diet quality and wellbeing, as well as the statistical methods that were used to assess the impact of these interventions. The systematic literature review was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guideline. This review covered all the fiscal interventions (i.e., food taxes and subsidies) and non-fiscal interventions (i.e., public information campaigns, advertising restrictions, nutrition/food labelling, nutrition and health claims, and nutrition education programmes) that were designed to reduce the demand for unhealthy food products and/or boost the demand for healthy food alternatives.
In a nutshell, results found that fiscal measures could potentially improve consumers' health, reduce the consumption of discretionary food products, and shift food purchases and consumption towards healthier food alternatives. It also appears that the joint implementation of taxes and subsidies (e.g., taxing sugary food and beverages and using the income generated to subsidise fruits and vegetables) is more effective than the individual implementation of food taxes and subsidies. Regarding the evidence on the impact of non-fiscal measures, results showed that public information campaigns and nutrition education are effective in increasing consumers' nutrition knowledge and intentions to make healthy choices but are only marginally effective in changing their buying and eating behaviour. Furthermore, the review found that restricting food promotions to children positively affected children's brand awareness, preferences, and requests to parents, both at the brand and category levels. However, to be effective, advertising restrictions should be implemented across all formats, both online and offline, beyond TV. Nutrition labelling and nutrition and health claims were found to be the most effective non-fiscal dietary interventions to encourage sustained positive behaviour changes of both food suppliers (e.g., reformulating their products) and consumers (e.g., reducing the consumption of discretionary food products).
The main findings of the literature review were presented to the stakeholders (Scottish Government and Food Standards Scotland) in October 2022. A short report that summarises the findings from the literature review was also shared with the stakeholders. The report also includes the research team's suggestions for dietary interventions that can potentially improve consumers' diet and nutrition in Scotland and whose effectiveness will be assessed in the remaining years of the project. After reading the short report, the stakeholders provided excellent feedback that guided the research team in writing up the findings and the selection of the dietary interventions that will be considered in the quantitative analysis planned for the next three years of the project.
The research team is finilising two journal papers on the finding of the literature review (one focussing on fiscal measures while the second focuses on non-fiscal measures).
Key findings and outputs from this project
Year 1 (literature review):
We found that fiscal measures can potentially improve consumers' health, reduce the consumption of discretionary food products, and shift food purchases and consumption towards healthier alternatives. We also found that the joint implementation of taxes and subsidies (e.g., taxing sugary food and beverages and using the generated income to subsidise fruits and vegetables) is more effective than the individual implementation of food taxes and subsidies. Regarding the evidence on the impact of non-fiscal measures, we found that public information campaigns and nutrition education are effective in increasing consumers' nutrition knowledge and intentions to make healthy choices but marginally effective in changing their buying and eating behaviour. Furthermore, the review of literature showed that restricting food promotions to children positively affected children's brand awareness, preferences, and requests to parents, both at the brand and category levels. However, to be effective, advertising restrictions should be implemented across all formats, both online and offline, beyond TV. Nutrition labelling and nutrition and health claims were found to be the most effective non-fiscal dietary interventions to encourage sustained positive behaviour change of both food suppliers (e.g., reformulating their products) and consumers (e.g., reducing the consumption of discretionary food products).
Year 2 (demand analysis):
The aim of the research for this section of the project was to measure Scottish consumers' food and drink purchases and their determining factors (e.g., price and household income) and evaluate their trends over time and across demographic groups. This has been done using the Family Food data, upon consultation with colleagues in Rural and Environment Science and Analytical Services (RESAS) and Food Standards Scotland (FSS); as this dataset includes better nutritional data (e.g., it includes information on vitamins and other micronutrients). After preparing the econometric data based on the Family Food dataset (including data on purchases, prices, expenditures and nutrition), the demand analysis was carried out. This includes conducting a descriptive analysis to gain first insights into the purchases of food and drinks in Scotland over time (from 2001 to 2022/2023) and across different economic and demographic groups (e.g., income level, ethnic group). We did the same analysis for the rest of the UK and investigated the differences between Scotland and the other UK nations. The analysis was done for all 262 available food categories (including eating out) in the data. Thereafter we proceeded with the demand analysis using the Almost Ideal Demand System (AIDS). This is an econometric analysis that allows us to estimate price and expenditure elasticities, which measure the sensitivity of the purchased quantities to changes in food prices and household expenditure on food and drinks.
Insights from this project
It is challenging to assess the impact of dietary intervention on the environmental quality of the diet. In other words, investigating whether improving the healthiness of the diet does not lead to a decrease in the environmental quality of the diet (e.g., through an increase in the demand for food products with a high carbon print). This is challenging due to the nature of the product included in market data. Many of them are unprocessed and it is very difficult to estimate their carbon print without making strong assumptions.
Recommendations for future projects
- Consider the impact on the whole diet and not only the food categories targeted by the policy interventions. We found that fiscal interventions significantly affect many non-targeted food categories leading to a significant impact on the whole diet.
- Consider the different dimensions of sustainability. We found that making the diet healthier does not necessarily lead to a more sustainable diet (environmentally and socially, e.g., animal welfare and provenance of the product).
- Consider the heterogeneity of impact across different groups of the population. For example, we found that the impact of dietary interventions varies with the level of deprivation in the household.
- Consider combining different types of dietary interventions (e.g., information-based interventions, nudges, market-based interventions, and regulatory measures) because the causes of unhealthy eating are diverse (e.g., price, information asymmetry, free riding).
This project has been completed.
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