Purpose: Childhood obesity is a serious health concern (World Health Organization (WHO), 2013) and advertising exposure is known to be a contributing factor (Institute of Medicine (IOM), 2006). In recent years consumers have expressed an increased interest in products appearing healthy and food companies have committed to changing their child-targeted marketing practices to promote a healthy lifestyle. The purpose of this paper is to examine depictions of physical activity in food advertising and assess how recognition of a promoted food's healthy and unhealthy traits influences dietary selections among youth in Southern Arizona in the USA. Design/methodology/approach: A content analysis of food advertisements aired during 2009-2013 (n = 534 and 354, respectively) identified changes to child-targeted food marketing messages. A structured interview determined differences in recognition of "juxtaposed beliefs" (i.e. that are contradictory and both healthy and unhealthy e.g. connecting exercise with a food high in sugar) among younger children, five to six years of age (n = 34) and older children, ten to 11 years of age (n = 34). Children were offered snacks to determine how this ability to recognize juxtaposition related to their dietary selections. Findings: There has been an increase in the frequency with which physical activity is depicted in advertisements for high-sugar foods. When presented with such advertising, a greater number of older than younger children recognized juxtaposed beliefs. Those younger children who showed recognition were more likely to select the advertised item, although this was not the case with older children. Research limitations/implications: The findings from this research relate to children's responses to advertisements for sugared cereal that depict physical activity and may not be generalizable further. Practical implications Children who are able to recognize both the healthy and unhealthy aspects of food are paradoxically likely to find it more appealing. Given the increased practice of associating high-sugar foods with physical activity in child-targeted food marketing, this raises concerns for nutrition education strategies, and the regulation of food marketing to children. Originality/value: Little research has examined the depiction of physical activity in food marketing targeting children, nor children's ability to recognize, and react to, juxtaposed beliefs regarding a product's healthfulness.