"London has learned from this and it will build its games around legacy and sustainability," Rogge said. London, with a 9.3 billion pound (USD 13.9 billion) budget for venue construction and regeneration, is struggling to secure private funding for the athletes' village and has moved some venues to save money.

Rogge said the Beijing Games had left China with immense benefits from infrastructure improvements, a new airport, subway lines, sports facilities and environmental upgrades.

Rogge said the Olympics have long been a force for social, urban and political change, citing the impact on Tokyo (1964), Seoul (1988) and Barcelona (1992).

"Benefits like these don't happen by accident," he said. Rogge delivered the "Pierre de Coubertin Lecture" organized by the RSA, which was founded in 1753. De Coubertin, a French baron who founded the modern Olympics, spoke to the RSA in 1904.

Rogge's speech coincided with weeklong meetings in which Chinese organizers are passing on lessons learned from the Beijing Games to London organizers.

Rogge praised London officials for trying to encourage young people to get into sports, citing figures that British children now spend an average of 5 hours, 20 minutes a day glued to television screens.

Rogge, who is waging a campaign against youth obesity, said 22 million children worldwide under the age of 5 and 1 in 10 school-age children are overweight.

"These inequalities result in an unjust and unhealthy global society," he said.