Globally, while some countries, including Ireland, South Korea and Turkey, define children in their food marketing legislation as persons aged up to 18 years, most food marketing policies only protect younger children [13, 14•, 18••, 31].

One of the reasons why older children are not commonly within the scope of international food marketing laws is because they are considered to have greater cognitive capacity than younger children and are viewed as less vulnerable to economic exploitation. However, evidence shows that food marketing also negatively influences adolescents. Adolescents are more likely to be influenced by their peers and are reward driven, impulsive and vulnerable to the promotion of products that provide immediate gratification [32, 33]. They have more purchasing power than younger children with access to their own money [34], and consumption levels of unhealthy foods and beverages are particularly high and concerning from a public health perspective [5, 6].

Governments have also faced challenges when trying to introduce laws to protect children up to age 18 [14•, 24, 27]. For example, during the policy development of a bill to restrict food and beverage advertising to children, the Canadian government reduced the age limit from 17 years old to 13 years old [27, 35]. Reasons for this reduced age threshold may relate to the argument (by those that oppose the legislation) that it would be too hard to discern food marketing that is ‘directed to’ a 17-year-old rather than an 18-year-old [14•, 24–26, 36, 37] or that marketing ‘directed’ or ‘targeted’ at adolescents would be too similar to marketing intended for adults [14•, 24, 37].

Under Article 24 of the UNCRC children are defined as ‘every human being below the age of 18 years unless, under the law applicable to the child, majority is attained earlier’ [38]. This is relevant as the UN Human Rights Council have interpreted a child’s right to health, enshrined in Article 24, as including the protection of children from unhealthy food and beverage marketing [15, 17, 22, 23, 38, 39]. All but two UN Member States have ratified the UNCRC and therefore have the legal obligation to fulfil the right of the child to enjoy the highest attainable standard of health and therefore the obligation to restrict unhealthy food and beverage marketing to children aged 18 years and under [13, 21, 40, 41]. Therefore, given the evidence base that exists to show that adolescents are vulnerable to marketing practices and the UNCRC legally requiring protection of children up to 18, governments should ensure their legal response defines children as ‘up to 18 years of age’.

Most countries focus on restricting food marketing through broadcast channels, particularly child-specific broadcasting (mainly television) [18••, 31] as it is easier to design and enforce compared to other settings and media and is viewed as more politically acceptable [14•]. To protect all children from all unhealthy food and beverage marketing, it is essential that the legislative scope includes unhealthy food marketing across all media and settings and all marketing techniques that children are exposed to [11, 14•, 42••]. This includes school settings; retail environments (product placements and price promotions in food stores); outdoor advertising (e.g. billboards); marketing in schools (including advertising, promotion and sponsorship); marketing in other children’s settings such as recreational facilities and event venues (including advertising, promotion and sponsorship); marketing online (including social media); advertising in broadcast media (television, cinema and radio); child-directed marketing on food packaging; sponsorship of sports and other major public events; and advertising on public transport (bus shelters, trains) and print media. [11, 14•, 42••].

Several countries have introduced comprehensive food marketing restrictions, across all media and settings, but are limited by a focus on ‘child-directed’ marketing content and exemptions for brand advertising [13, 14•]. In Quebec, Canada, under the Consumer Protection Act, all commercials are prohibited where children (< 13 years) comprise more than 15% of the audience, and the product featured is exclusively designed for, or appeals to, children [43]. In Ireland, the Children’s Commercial Communication Code only applies where commercial communications target children under 18 and are broadcast during programmes where children comprise more than 50% of the total audience [44].

As part of the broadcast aspect of the Food Labelling and Advertising Law, the Chilean Government originally designed their restrictions as any unhealthy food advertising on television programmes considered to be (i) ‘child-targeted’, (ii) where > 20% of the audience consists of children aged < 14 years, and (iii) where advertising appeals to children by including characters, toys or other strategies considered to be ‘directed to children’ [18••, 45]. Research has shown that while a ‘child-targeted’ approach did reduce the exposure of advertising by 35% for pre-schoolers and 52% for adolescents, it did not eliminate television advertising for products subjected to the law [46]. The authors of this study suggest that the reasons for the remaining exposure of unhealthy food and beverage marketing on television is likely a consequence of food marketing outside of child-targeted programming and with the difficulties in interpreting ‘child-directed’ marketing and thus ensuring compliance with the law [46]. In June 2018, the Chilean Government adapted the design of the legal response to replace the ‘child-targeted’ definition with a time-based restriction that banned all unhealthy food advertising on television channels between 6am and 10 pm. While there has been no evaluation of this later policy amendment, it is expected that it will eliminate the vast majority of children’s exposure to unhealthy food advertising on television [46]. Similarly, the UK has recognised the limitations with its original legislative approach to broadcast legislation, which stated ‘no medium should be used to advertise HFSS products, if more than 25% of its audience is under 16 years of age’ and passed legislation that introduced a 6am until 9 pm watershed of unhealthy food and beverage marketing, although implementation has been stalled indefinitely [47, 48].

This approach of restricting unhealthy food marketing that is ‘targeted at’, ‘directed at’, ‘appealing to’, ‘child-directed’, specific to ‘children’s programming’ or specific to ‘children’s media’ is limited for several reasons [13, 14•, 34]. With this approach, governments have to discern exactly what is subject to the legal response. Children’s media or programming (particularly television) is often defined using audience thresholds, using the proportion of children in the audience. This is problematic as many children consume the same media and attend the same settings as adults, so a small proportion may represent a very large number of children [34]. The frequency of these mixed-audience environments increases as children grow older; therefore, the use of audience thresholds becomes increasingly difficult. Similarly, marketing techniques that are defined as being targeted to children are commonly determined by a ruling of whether the marketing is ‘child-appealing’; however, understanding what is ‘child-appealing’ is nuanced and subjective and therefore incredibly difficult to implement and enforce [27, 49]. Therefore, ‘child-directed’ marketing definitions are not sufficient as children are exposed to a wide range of media sources and content that are not specifically ‘targeted’ or ‘directed’ at them [34].

Brand marketing is a key marketing tactic where a food company advertises their master brand or logo, which emphasises a corporate brand instead of a specific product. However, including brand marketing within the scope of a legal response can be difficult, and globally, there are no legal responses of unhealthy food and beverage marketing that include brand marketing within their scope [31]. This is, in part, because the legal design is underpinned by a nutrient or food classification system, which has been designed to classify foods and beverages as ‘permitted’ or ‘not permitted’ to be marketed, not brands. Therefore, marketing that does not feature a food or beverage product is exempt.

Exemptions of brand marketing are a public health issue as evidence shows that advertising of brands that are primarily associated with unhealthy foods and non-alcoholic beverages (e.g. quick service restaurants or confectionary) increases reward pathways in the brain and selection and consumption of unhealthy products [50, 51]. Similarly, unhealthy food sponsorship (from the local to elite level), which is often reciprocated through the advertisement of sponsors' brands, has been shown to increase brand awareness and preference for branded products [52, 53]. Legal responses that do not incorporate brand marketing may also result in the unintended consequence of shifts in marketing spend from restricted forms of food marketing to unrestricted marketing of brands and logos.

This can be addressed by creating a brand classification system for assessing which brands will be subject to a restriction. For example, a brand’s top five selling items by market share could be identified, and if three or more of these products are not permitted to be marketed according to the legislated food classification system, then any associated brand advertising could also be prohibited.

Only with a broad definition of marketing will every child be given the same level of protection, regardless of how they access their media content. Further, a comprehensive legislative response that covers all types of unhealthy food and beverage marketing, across all settings and media, will minimise shifts of marketing practices from regulated to unregulated media, settings and times, as was seen in the earlier phases of regulating tobacco marketing [54–56].

Given the inadequacies of a ‘child-directed’ approach, governments need to consider how each setting, media and technique will be regulated, as a blanket ban on all unhealthy food and beverage marketing is unlikely to be a realistic alternative. To ascertain the most appropriate legislative design, each media, setting and technique can be assessed to understand the practicalities of effectively restricting the exposure of unhealthy food and beverage marketing in the specific context.

Typically, most marketing practices can be categorised into a setting-based, time-based, media-based or content-based design approach (see Table 1). For example, in settings where there is frequently a high number (not proportion) of children present at all times (e.g. public spaces or retail environments), a whole-of-setting ban on unhealthy food and beverage marketing should be considered. For media types that are more linear in nature (e.g. broadcast), a time-based approach may be utilised, restricting all unhealthy food and beverage marketing between times when large numbers (not proportions) of children are in the audience. In other media, where the audiences are highly mixed between adults and children and when the advertising models are complex and difficult to control during specific hours or times (e.g. online media), a media-based restriction that covers the entire medium, at all times, should be considered. For any marketing media, settings or techniques where it would be ineffective or inappropriate to be regulated with a time-, media- or setting-based legal design, a content-based regulation could be considered. A content-based design would ban unhealthy food and beverage marketing where the creative content of the marketing message is considered to be ‘directed to children’. This should not be considered as the primary legal design but rather a default design approach that captures any unhealthy food and beverage marketing that children are exposed to that is not captured in the setting-, time- and media-based design approaches. For example, this may be appropriate for marketing of product packaging of unhealthy foods and beverages or during television times that are outside of the specified time-based restrictions. Table 1 categorises these different approaches to regulatory design.

Food and nutrient classification systems are those that scientifically determine whether a food may or may not be marketed under a relevant food marketing regulatory regime. Many countries have adopted a nutrient-based classification, often with pre-defined food categories that are considered within scope of the legal measures [18••]. Governments can adapt regional nutrient profile models developed by the WHO [57–59] or apply the NOVA classification system [60], which categorises foods according to the levels of processing. In reality, most countries develop their own systems and in doing so end up using a food classification model that is not comprehensive enough to cover all foods and beverages that are harmful to health. For example, almost all countries do not restrict the marketing of beverages containing non-nutritive sweeteners, despite recommendations that they be banned within WHO nutrient profile models [58, 59, 61] and the increasing evidence that these products increase the risk of adverse health outcomes [61]. Weaker food classification models can weaken the strength of the legislation and the intended effect.

The reasons for the adoption of weaker food classification models again likely relate to the powerful opposing force of the food and beverage industry. To protect against both domestic or international legal and trade challenges, governments must ensure that the evidence base for the foods chosen is scientifically robust and not unjustifiably discriminatory against certain food groups or products, particularly those from other countries [14•, 62]. Where certain food groups are exempted from being in scope of the law by a government, for example, certain types of dairy products, those exemptions must be scientifically justified and not be arbitrary or discriminatory in nature [14•, 62]. A strong classification system that aligns with national dietary guidelines is critical, but the WHO models are a strong starting point because they are evidence-based.