June 30, 2024 – ANA BALSA, CECILIA NOBOA, AND PATRICIA TRIUNFO

Previously published on VoxEU on June 27, 2024.

Overweight and obesity have risen dramatically in recent decades in both developed and developing countries. Numerous policies have been developed to help curb this increase. The success of many of these policies depends heavily on correctly identifying the factors that hinder a healthy diet. This column documents an intervention that nudged customers of a supermarket chain in Uruguay to improve their eating habits. The intervention appears to be effective by increasing salience and redirecting consumers’ attention, rather than by providing new information.

The World Health Organization (WHO) refers to the “escalating global epidemic of overweight and obesity” as one of the most challenging health issues worldwide (WHO 2024). In 2022, 43% of the world’s adult population was overweight and 16% were obese, more than twice the obesity rate of 1990 (WHO 2024). Uruguay is no exception, with two out of three adults being overweight or obese (Ministry of Public Health 2013).

Since the late 1980s, the consumption of fruits, vegetables, fibre, and complex carbohydrates has shown a sustained reduction (Popkin et al. 2012, PAHO 2015). Conversely, the volume sales of ultra-processed foods and drinks, characterised by high levels of fats, sugar, and sodium, increased by 44% between 2000 and 2013 (PAHO 2015). Greater accessibility to energy-dense, low-nutrition-value food has been identified as a key factor contributing to diet deterioration and increases in overweight, obesity, and non-communicable diseases (Zobel et al. 2016).

To tackle and prevent non-communicable diseases, the WHO recommends implementing public policies that discourage the consumption of ultra-processed foods with unfavourable nutritional profiles (PAHO 2015). Several countries have attempted to curb the upward trend in unhealthy food consumption by imposing taxes on sodas (Dubois 2007, Dubois et al. 2020) and junk food (Dubois 2007), changing advertising practices (Dubois et al. 2018, Griffith et al. 2017), posting front-of-package labelling (Barahona et al. 2023) and food items’ caloric content (Aranda et al. 2021, Cawley et al. 2020), or outright banning fast food outlets (Brown et al. 2022) and the sale of junk food in schools (Leonard 2017).

The success of these policies relies heavily on correctly identifying the drivers behind the sustained growth in the uptake of ultra-processed food and sugar-sweetened beverages, as well as the barriers that impede a healthy diet.

Behavioural nudges

New developments in behavioural economics, an interdisciplinary field that combines psychology and economics, show that people making decisions are often influenced by cognitive biases, emotions, and other psychological factors. To improve decision-making in a context of well-identified systematic deviations from rationality, behavioural economics proposes the use of nudges, defined as “any aspect of the choice architecture that alters people’s behaviour in a predictable way without forbidding any options or significantly changing their economic incentives” (Thaler and Sunstein 2008, see also Andersson and Nordblom 2022).

Nudges have been implemented in different contexts, including tax compliance (Andersson et al. 2023, Andersson and Nordblom 2022), energy conservation (Allcott and Rogers 2014), health prevention (Milkman et al. 2022), education programmes (Damgaard and Nielsen 2018), and early childhood interventions (Bloomfield et al. 2023).

In particular, systematic behavioural biases held by consumers promote and reproduce unhealthy behaviours. Present bias discourages individuals from investing in behaviours and actions that are costly in the present and beneficial in the future, such as exercising or eating fresh vegetables and fruit. Status quo bias tends to reproduce past behaviour without rationalising its costs and benefits. Limited attention and decision fatigue may lead to inaction as people avoid making decisions that are complex or require mental effort (such as changing habits). Finally, the social environment is a strong determinant of behaviour – we are less likely to incorporate healthy behaviours if we are surrounded by people who are sedentary or engage in unhealthy eating.

The effect of nudging healthy food choices

In a recently published study (Balsa et al. 2023), we evaluate the impact of an intervention that involved sending WhatsApp messages to regular customers of a supermarket chain in Uruguay with the aim of nudging healthier food purchases.

We randomly assigned a subset of 1,590 regular customers to receive three short, simple messages per week for eight weeks (from July to September 2020). These messages focused on various topics: cooking at home, eating vegetables, fruits, healthy snacks, legumes and fish, and conscious and healthy eating. Their design aimed at addressing biases that are likely to lead to suboptimal food choices (see Figure 1). For example, sending recurrent information via WhatsApp about the benefits of healthy foods helps address present bias. Proposing simple actions mitigates inaction due to inattention and decision fatigue, and highlighting public figures’ good habits makes the messages more salient and signals a social norm.

Figure 1 Intervention design and behavioural biases

We found that, on average, customers responded favourably to the messages: they increased their purchases of fruits and vegetables by 8% and substituted sugar‐sweetened beverages for sugar‐free ones.

However, as with other behavioural economics experiments, reactions to nudges were qualitatively heterogeneous. Customers more likely to be uninformed or to suffer from cognitive inattention or present bias (those with lower education, lower income, or younger children) were more likely to respond directly to the nudges, increasing their purchases of foods and vegetables.

On the other hand, better-educated customers with higher incomes or no young children tended to substitute higher-calorie ultra-processed foods with lower-calorie ones. These customers even ended up increasing their total spending on this food, without affecting or even decreasing, in certain cases, the total number of calories or fats purchased.

These results indicate that interventions may need to discourage the consumption of ultra-processed foods in addition to promoting the purchase of healthy foods. The effects do not persist in the long term, suggesting that attention management, rather than information, is the primary channel driving the changes in behaviour.

Policy implications

The intervention appears to work by increasing salience and redirecting consumers’ attention, rather than by providing new information.

The lack of persistence of the effects of the intervention (similar to the findings in Belot et al. 2018) suggests that recurrent messaging or stronger incentives may be needed to encourage permanent nutritional changes. Stronger incentives could include discounts or other financial incentives, possibly attached to personalised goals to take advantage of the large heterogeneity in customers’ reactions.

The findings of our study suggest several policy implications for addressing overweight and obesity through behavioural interventions. The chosen nudges are effective in the short term by increasing the salience of healthy options and temporarily redirecting consumers’ attention to them, rather than by providing new information. However, the intervention was not successful at decreasing expenditure on ultra-processed foods, indicating a need to include explicit information on the adverse health consequences of these foods when designing messages.

Interventions should target individuals according to their socioeconomic characteristics, educational levels, and household compositions, proposing messages and incentives adapted to their backgrounds and consumption patterns. Personalised nudges are more effective than universal strategies.

In summary, while nudges are a promising tool for promoting healthier eating habits, their design and implementation need careful consideration to address all the targets of a healthy diet, ensure long-term effectiveness, and be responsive to the specific needs and behaviours of different demographic groups.

Ana Balsa is a Professor at the Department of Economics of Universidad de Montevideo and holds a PhD from Boston University.

Cecilia Noboa is a research assistant at the Department of Economics at Facultad de Ciencias Sociales at Universidad de la República, Uruguay. 

Patricia Triunfo is a Professor at the Department of Economics at Facultad de Ciencias Sociales at Universidad de la República, Uruguay. 

References

Allcott, H, and T Rogers (2014), “The short-run and long-run effects of behavioral interventions: Experimental evidence from energy conservation”, American Economic Review 104(10): 3003–37.

Andersson, H, P Engström, K Nordblom, and S Wanander (2023), “Nudges and threats: Soft versus hard incentives for tax compliance”, Economic Policy, eiad017.

Andersson, H, and K Nordblom (2022), “Nudges and threats: Soft and hard incentives for tax compliance”, VoxEU.org, 29 November.

Aranda, R, M Darden, and D Rose (2021), “Measuring the impact of calorie labeling: The mechanisms behind changes in obesity”, Health Economics 30(11): 2858–78.

Balsa, A, C Noboa, and P Triunfo (2024), “Nudging healthy food choices through e‐messages in a supermarket”, Health Economics 1–21.

Barahona, N, C Otero, and S Otero (2023), “Equilibrium effects of food labeling policies”, Econometrica 91(3): 839–68.

Belot, M, N Berlin, J James, and V Skafida (2018), “The formation and malleability of dietary habits: A field experiment with low income families”.

Bloomfield, J, A Balsa, and A Cid (2023), “Using behavioral insights in early childhood interventions: The effects of Crianza Positiva e-messaging programme on parental investment”, Review of Economics of the Household 21(1): 95–130.

Brown, H, H Xiang, V Albani, L Goffe, N Akhter, A Lake, S Sorrell, E Gibson, and J Wildman (2022), “No new fast-food outlets allowed! Evaluating the effect of planning policy on the local food environment in the North East of England”, Social Science and Medicine 306: 115126.

Cawley, J, A Susskind, and B Willage (2020), “The impact of information disclosure on consumer behavior: Evidence from a randomized field experiment of calorie labels on restaurant menus”, Journal of Policy Analysis and Management 39(4): 1020–42.

Damgaard, M T, and H S Nielsen (2018), “Nudging in education”, Economics of Education Review 64: 313–42.

Dubois, P (2007), “Obesity’s on the rise – let’s have the courage to tax junk food!”, VoxEU.org, 17 October.

Dubois, P, R Griffith, and M O’Connell (2018), “The effects of banning advertising in junk food markets”, Review of Economic Studies 85(1): 396–436.

Dubois, P, R Griffith, and M O’Connell (2020), “How well targeted are soda taxes?”, American Economic Review 110(11): 3661–704.

Griffith, R, M O’Connell, and P Dubois (2017), “The effects of banning advertising in junk food markets”, VoxEU.org, 31 March.

Leonard, P (2017), “Do school junk food bans improver student health? Evidence from Canada”, Canadian Public Policy 43(2): 105–19.

Milkman, K L, L Gandhi, M S Patel, H N Graci, D M Gromet, H Ho, … and A L Duckworth (2022), “A 680,000-person megastudy of nudges to encourage vaccination in pharmacies”, Proceedings of the National Academy of Sciences 119(6): e2115126119.

Ministry of Public Health, Uruguay (2013), Second national survey on risk factors, Ministry of Public Health.

Pan American Health Organization (PAHO) (2015), Ultra-processed food and drink products in Latin America: Sales, sources, nutrient profiles and policy implications, Washington: Pan American Health Organization.

Popkin, B, L Adair, and S Ng (2012), “Global nutrition transition and the pandemic of obesity in developing countries”, Nutrition Reviews 70: 3–21.

Thaler, R H, and C R Sunstein (2008), Nudge: Improving decisions about health, wealth, and happiness, Yale University Press.

World Health Organization (WHO) (2024), “Obesity and overweight”, Fact sheets, World Health Organization, 1 March.

Zobel, E, T Wansen, P Rossing, and B von Scholten (2016), “Global changes in food supply and the obesity epidemic”, Current Obesity Reports 5: 449–55.

Photo by Matheus Cenali: https://www.pexels.com/photo/assorted-vegetable-lot-2733918/