There is growing concern regarding the rapidly increasing rate of obesity in childhood, which has become epidemic in some areas and is on the rise in others, with an estimated 17.6 million obese children worldwide; particularly, there are increasing trends in emerging economies. The early onset of obesity, which is a major risk factor for a number of non-communicable diseases, including diabetes mellitus, coronary heart disease, hypertension and some forms of cancer, needs to be addressed with high-impact strategies for prevention and, where this fails, with clinical management [1–3]. Specific attention has recently focused on limiting inappropriate (in amount and typology) caloric intake within a context defined as an “obesogenic environment” of childhood, which is an environment where TV viewing, advertising, marketing strategies promoting food associated with gadgets and snacking are identified as possible risk factors [4–7].
Recent literature and scientific research has therefore focused on television and advertising and assessed their influence on children’s eating behaviours, with results showing an increased daily caloric intake. Ample studies investigating the effects of TV viewing on total energy intake have concluded that there is a positive effect of increased screen time on energy intake in children and adolescents [8, 9]. Other studies have considered the short- and long-term effects of advertising on children’s food intake and the promotion of unhealthy diets [4, 10], demonstrating a causal link between food consumption and television exposure and advertising . Snacking during screen time is often associated with high, energy-dense products, therefore undermining the healthy balance of energy intake [11, 12]. In addition, other studies suggest the existence of a specific gender effect in the sense that boys seem to be more susceptible to food cues than girls . There is also growing evidence that children with greater exposure to commercials appear to be more responsive to food promotion messages than children with lower previous advertising exposure .
In this context, a long-standing yet under-investigated factor that might influence energy intake is the promotion of food to children in association with gadgets, usually toys, aimed at capturing the attention of the child and increasing loyalty to the brand or product; this could be related to obesogenic effects . Considering the possible link between gadgets and an obesogenic effect, a recent ordinance in the U.S.A. was implemented to prohibit the distribution of toys and other incentives to children in conjunction with meals, foods, or beverages that do not meet minimal nutritional criteria .
The debate over such regulatory measures is ongoing in several other countries as well, both in established and emerging economies. In Latin America, where obesity is an emerging trend, particularly in children, the need for regulatory proposals grounded on strong evidence has faced a lack of experimental information on the behavioural factors related to obesity. In such geographical areas, decision makers often refer to evidence translated from experimental studies that are usually performed in North American or, more generally, that refer to an Anglo-Saxon cultural setting [4, 5]. Such studies are indeed designed to detect an excess of caloric intake under certain experimental conditions, particularly exposure to TV watching and snacking, advertising or branding [4, 5, 10, 12, 16].
To fill this gap, a wide experimental study has been conducted in three Latin American countries (Mexico, Brazil and Argentina) that are facing a steep growth in obesity rates in children (with obesity rates of 41.8% , 22.1%  and 19.3%, respectively ). The primary aim of this study was to assess whether including toys in food packages increases the amount of food eaten by children during a snacking occasion.
Given the abovementioned evidence of the role of TV and advertising in promoting an excessive consumption of (branded) food in children , the children were also exposed to TV and advertising during the experimental sessions, to adjust for both their potential confounding effects and their intrinsic relevance as intervening factors.
This resulted in a factorial study design, which, at the price of a certain logistical and analytical complexity, aimed in a controlled situation to evaluate the effects on the amount of snacks eaten by the children when the children (i) had food presented with toys in the package, (ii) were exposed to TV when snacking, (iii) were exposed to advertising (at an increasing intensity during TV exposure) and (iv) had potential interactions from a combination of all these factors.