Signal said McDonalds and Coke are greatest product sponsors of New Zealand sports.
"And one of our most popular sports, rugby, has the unhealthiest sponsorship by far with 23 percent of brands and logos linked to unhealthy food. In contrast, netball has only 1 per cent linked to unhealthy food.
"Given the recent increase in obesity amongst New Zealand children this is of considerable concern.
"Currently, 11 per cent of children aged 5 to 14 are obese, up from 8 per cent in 2006 and 2007, and at least 20 per cent are overweight.
"The consumption of junk food is a significant contributor to this problem.
"Obesity is associated with a range of health problems including childhood diabetes, and heart disease, diabetes and cancer in later life.
"Our children deserve to be protected from the pressure to eat junk food while enjoying healthy outdoor activity, and parents need to be supported against pester advertising in their efforts to promote healthy eating to their children."
Signal said counting sponsor logos probably underestimates the extent of sponsorship of sports.
"Tactics included the use of 'Player of the Day' certificates for budding All White football players as young as four, and promotion of Powerade by the All Blacks. Powerade is not generally recommended for children."
Healthy food and beverage brands do also sponsor sport, with 21 per cent of logos on rugby websites linked to healthy foods, with cricket the next highest with 5 per cent.
The researchers said increasing such healthy sponsorship and highlighting the affect a good diet has on athletic performance is a way to support children eating a nutritious diet.
All the sports administrators interviewed in the study said the main benefit of sponsorship was financial, and although many were concerned with associating their sport with unhealthy foods or beverages, others considered sponsorship income to be more important.
The study recommended sports codes requiring members place a higher priority on health when selecting sponsors, and government regulation and funding to replace unhealthy food sponsorship with healthy sponsorship, just as was done for tobacco.