Global Food Research: Will front-of-the-package warning labels change our eating habits?


The Global Food Research Program shares their perspective on targeting ultra-processed foods with front-of-the-package warning labels, which is the only impactful approach

In the past decade a major addition to our understanding of how the modern food supply is affecting adversely the risks of all Noncommunicable Diseases (NCDs), including obesity, diabetes, hypertension, major cancers – all of which are nutrition-related as either diet or obesity or both are major determinants. At the same time countries have begun to work out sets of regulations and laws to attempt to shift our diets toward reduced intakes of these foods and toward healthier eating. The Global Food Research Program at the University of North Carolina is a leading institution working to provide research related to the design of Front-of-the-Package food labelling and working with collaborators globally to evaluate them.

The significant health impact of ultra-processed food

A large and growing body of research has highlighted the large, significant impact of excessive consumption of ultra-processed food on the risks of noncommunicable diseases (NCDs), including obesity, diabetes, and hypertension. An important link was a random controlled trial with a crossover design (each person was his or her own control) that a highly respected team of researchers at the US National Institutes of Health (NIH) conducted in 2019.1 The researchers fed normal-weight adults a diet of real food for two weeks and a diet of ultra-processed food for another two weeks. While consuming the real food the adults lost 0.9 kilograms, but while consuming the ultra-processed food the same adults gained 0.9 kilograms. Biomarkers for diabetes, hypertension, and hyperlipidemia, among others, increased equally significantly with the ultra-processed food diet. Each group started with one diet regimen and then shifted to the other.1

The 2019 NIH trial is important, as previously all the studies discussed below were observational and therefore focused on subsequent health risks according to the amount of ultra-processed food in people’s diets. Although these studies were controlled for a long list of potential confounders, such as physical activity and smoking, residual confounding never can be discarded. This 2019 NIH study put all subjects into a controlled food environment for a month.

The researchers provided each group foods with the same distributions of fiber, protein, carbohydrates, fats, and total energy. However, while ultra-processed beverages can lower energy density and total energy, all ultra-processed foods are higher in energy density than real foods. The members of the two groups were allowed to eat ad libitum or the amount they wanted. As a result, the same individuals consumed 500 kilocalories more when they were in the ultra-processed food group than when they were in the real food group, which is important. Whether the mechanism involved is hyper-palatability, energy density, or both requires further study.

This NIH work is supported by 19 wide-ranging cohort studies in Europe, the United States, Brazil, and elsewhere. These studies, mainly of adults but a few of children, link increased proportions of ultra-processed food in the diet with increased risks of obesity; many measures of cardiovascular disease (CVD), including diabetes, hypertension, overall CVD, and CVD mortality; cancer; and total mortality.2-18

The rapid growth in ultra-processed food consumption across the globe

Increasingly, pre-packaged foods and beverages are readily available in virtually every community across all parts of the globe, regardless of income level or population density.18-23 Combined with aggressive marketing of these products, this availability has dramatically affected the way people eat in many countries, resulting in less healthy diets.24-27

Many prepackaged foods are processed with high levels of added sugars, sodium, saturated fats, and refined carbohydrates.27-31 Research has connected these nutrients of concern to increased obesity and chronic nutrition-related diseases.24,32-36 The emerging evidence indicates that malnourished infants and preschoolers are fed these processed foods and beverages. Recent studies associate ultra-processed food with reduced length for age.37

The 2019 A. M. Pries et al. study is the only one that examines infant consumption of any ultra-processed food aside from infant formula, which fits into a different category but is also ultra-processed. We need longitudinal studies on cohorts with more recent full dietary intake data to reflect the increasing shift in ‘low- and middle-income countries’ infant diets toward ultra-processed food.28-30,37-39

Front-of-the-package warning labels empower informed choices:

Consumers need a clear and easy way to make healthier choices among the array of available products.

Shoppers prefer simple front-of-the-package (FOP) labels that are immediately visible and quickly evaluated.40,41 Labels that minimise effort allow customers to rapidly determine which products are healthier and thereby actually increase the intention to purchase a healthy product or, conversely, decrease the intention to purchase an unhealthy product.42-46

Among the several labelling approaches that have been devised, simple negative warning labels that identify unhealthy products are most effective in discouraging junk and ultra-processed food choices.47

Why not a healthfulness score or a traffic light?

When compared to other FOP labels, FOP nutrient warning labels may have different effects on consumer behaviours and ultimately on diet-related health outcomes. For example, some FOP labelling systems, such as Nutriscore or Australia’s Health Star Ratings, create summary indexes of multiple nutrients, including nutrients of concern, beneficial nutrients, or beneficial ingredients, to present a product’s overall nutritional profile on a continuum from least to most “healthy.” In these systems, the levels of nutrients of concern to the consumer are not clear, and often one nutrient can offset another in a way that impacts NCD concerns, for example, a sugar-sweetened beverage (SSB) fortified with vitamin C.

Other FOP label schemes, like the traffic light label, that colour-code multiple nutrients convey complex and sometimes contradictory information, such as a product high in one nutrient of concern but low in another, requiring consumers to evaluate all the information to come to an assessment of overall healthfulness. A consumer can become confused when a nutrient of concern, say sugar, is offset by another, say sodium. In contrast, nutrient warnings are binary, focused on nutrients of concern, and signal to consumers the presence or absence of high levels of these nutrients of concern.

These distinctions may have important implications for how labelling systems influence consumer behaviour. For example, FOP labelling systems that do not call attention to nutrients of concern or present potentially conflicting information may be more likely to encourage consumers to choose the “healthier” option among still unhealthy products rather than the proven healthy options.

Chilean studies evaluating the first year of required warning label implementation are emerging. The first study on focus groups of lower- and middle-income mothers suggests profound changes in food purchasing linked not only with the knowledge mothers gained from these labels but also with children telling their mothers not to purchase unhealthy products.48,49 We anticipate that future studies will show large changes in purchases of key unhealthy foods with warning labels.

Another Chilean evaluation of the impact of phase 1 of the implementation of the SSB warning label found that in the first year SSB purchases declined 23.7% in millilitre per capita per day.50 The phase 2 and 3 cutoffs will affect higher proportions of unhealthy foods and beverages. Chile was the world’s top country in per capita SSB consumption at the time the law went into effect.

What experiments have already been done?

Experiments in many countries with FOP warning labels on SSBs linked warning labels with decreased purchases of SSBs, decreased perceptions of their healthfulness,51,52 and decreased purchasing intent.51-53

A 2017 study comparing FOP warning labels to the industry-endorsed guidelines for daily allowance (GDA) and traffic light label systems found that warning labels were better able to help consumers correctly identify products high in unhealthy nutrients and that consumers perceived products bearing warning labels as less healthy than the same products featuring GDA or traffic light labels.54

Another 2017 study in Uruguay comparing children’s perceptions of food products with warning versus traffic light labels found that warning labels had greater relative impacts on children’s food choices compared to the traffic light system.55

Studies using eye-tracking technology to evaluate the influence of nutritional warnings alongside GDA labels have found that nutrient-based warning labels attract consumers’ attention and help them more quickly and easily identify whether a product is unhealthy.56,57

The only traffic light label study to show a positive impact combined financial incentives with the traffic light system.58 No study has shown that Nutriscore, GDA, or traffic light labels significantly impact food or beverage purchases.

A recent in-depth review of all FOP warning label systems highlights the critical value of warning labels in reaching consumers and impacting their behaviours.59 This scoping review found that many experimental studies of FOP nutrient warning labels focused on outcomes, such as comprehension and behavioural intention, but that considerable gaps in the evidence remain, particularly in the areas of negative affect and social interactions, precluding a clear understanding of the pathway through which nutrient-based FOP warnings change behaviour.

The studies found that nutrient-based FOP warnings visually attracted consumers, were easy to understand, helped consumers identify products high in nutrients of concern, and discouraged consumers from purchasing unhealthy products but do not contain as much information as other FOP labelling systems.


Please note: This is a commercial profile

1. Hall KD (2019 ) Ultra-processed diets cause excess calorie intake and weight gain: A one-month inpatient randomised controlled trial of ad libitum food intake. Cell Matabolism 30: 1-10.

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Barry M Popkin

Jr. Distinguished Professor
Gillings School of Global Public Health
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