American broadcasting, unique among media industries, relied on sponsors and their ad agencies for program content from the 1920s through the 1950s. Some sponsors broadcast educational or culturally uplifting programs to burnish their corporate images. By the mid-1960s, however, commercial broadcasting had transformed, and advertisers could only buy interstitial minutes for interrupting commercials, during which they wooed cynical consumers with entertaining soft-sell appeals. The midcentury shifts in institutional power in US broadcasting among corporate sponsors, advertising agencies, and radio/television networks reflected a fundamental shift in beliefs about how to use broadcasting as an advertising medium.

Food advertisements on mainstream television have received less research attention than those on children's television. Little is known about how television food advertisements vary internationally or if there have been changes over recent years. We describe food-related television advertisements and the nutrient content of foods advertised during prime-time television in Ontario, Canada and the UK in 1991 and 2006. Information on what advertisements were broadcast were obtained from video recordings and audience research bureaux. Data on nutrient content of foods advertised were obtained from manufacturers and standard food tables. The proportion of advertisements that were food related decreased between 1991 and 2006 in both countries. The frequency of food-related advertisements was relatively constant in Canada but decreased between 1991 and 2006 in the UK. In 1991, advertisements for beverages and meals predominated in both countries. By 2006, food-related advertisements in Canada were dominated by meals and restaurants. In the UK advisements for food stores and beverages predominated. The ‘TV diet’ in Canada in 1991 was relatively high in fat, high in alcohol and low in fibre, compared to current recommendations. By 2006, this had changed to high in fat and sodium and low in fibre. The ‘TV diet’ in the UK in 1991 was high in fat, sodium, sugar and alcohol and low in fibre compared to current recommendations. By 2006, the UK ‘TV diet’ was high in sodium, sugar and alcohol and low in fibre. Foods advertised on ‘prime-time’ television do not reflect a healthful diet.