Many of the snacks were high in sugar, fat and salt
Vending machines stocked with unhealthy snacks in leisure centres run the risk of fuelling childhood obesity, warn experts.
Crisps and chocolate are on sale where children exercise despite being banned from schools and children's TV, the British Heart Foundation found.
And children's meals on offer at the 35 venues spot-checked were dominated by chips, nuggets, sausages and burgers.
The charity wants stricter regulation over the food choices available.
The report, which was prepared by the Food Commission, looked at leisure centres, bowling alleys, ice skating rinks and park cafes.
The average calorie content of vending machine snacks was 203 calories, which would take a seven-year-old 88 minutes of swimming to use up.
Fresh fruit was displayed at less than half of the venues visited, and nutritional information was displayed at just two of the venues visited.
The BHF said this severely limits the child's and parent's ability to assess the nutritional values of the products they are buying.
BHF chief executive Peter Hollins said: "It's fantastic that these kids are getting fit and having fun at the same time but this is being undermined by venues peddling junk food at them.
"Councils and leisure providers need to rigorously reconsider the food options they are providing and make it easier for parents and children to make healthier choices."
The charity is now calling for public and private sector providers to lead the way in ensuring healthy food options are available and easily identifiable.
It says it should be made a requirement that vending machines in publicly owned facilities are stocked with healthier products.
A Department of Health spokeswoman said: "We are fully committed to encouraging the adoption of healthy vending machines across the country and expect local authorities to make sure there are healthy food options available in their leisure centres."
Confectionery, crisps and sugary fizzy drinks have been banned from all school vending machines in England since September 2007.
Judy Hargadon, chief executive of the School Food Trust, said: "Convenience doesn't have to mean unhealthy.
"Many schools are using vending to offer pupils extra choice and independence whilst still keeping their options well-balanced and consistent."