Fast-food restaurants in the United States are 'disproportionately' targeting black children and kids in middle-income and rural areas, according to a newly published study.

Researchers at Arizona State University and University of Illinois at Chicago looked at 6,716 fast-food outlets nationwide to check the extent of indoor and outdoor marketing aimed at youngsters.

Marketing towards children ranged from free toys to ads featuring sports celebrities and cartoon characters, as well as play areas and promotions for kids' birthday parties.

Fast-food restaurants in the United States are 'disproportionately' targeting black children and kids in middle-income and rural areas, according to a newly published study

'Majority black communities, rural areas and middle-income communities are disproportionately exposed (to child-directed marketing) and specifically to indoor displays of kids' meal toys, a popular strategy among chain restaurants,' the study said.

'In light of these findings, it is important to urge the fast-food industry to limit children’s exposure to marketing that promotes consumption of unhealthy food choices.'

The enduring popularity of fast food is widely seen as contributing to an obesity crisis in the United States, where one in three adults are considered obese, according to the Centers for Disease Control.