"It's not stopped him from making the achievements that he has and that's a great message to be able to get out to people with diabetes," she said.
The walk was one of 26 around the country raising funds and awareness of the disease and how exercise can control it.
Sir Steve battled diabetes to win his record-breaking fifth Olympic Gold medal at the Sydney games in the coxless fours.
Benet Middleton, of Diabetes UK, told BBC News Online that Sir Steve "lead from the front" for most of the six-mile walk.
Role model
Mr Middleton added that Asian actor Saeed Jaffrey, jazz singer Mari Wilson, radio presenter Steve Allen and TV's Simon Biagi had also attended the launch.
The charity's Srabani Sen told BBC News that Sir Steve was a great role model for people with the condition.
"It's not stopped him from making the achievements that he has and that's a great message to be able to get out to people with diabetes," she said.
One and a half million people in the UK have diabetes, according to the charity.
It is the main cause of blindness and could also lead to strokes, heart and kidney disease, Ms Sen said.
People who were unfit, overweight, older than 40, Afro-Caribbean or Asian in origin or, like Sir Steve, had a family history of diabetes were more vulnerable, she added.
Sir Steve, from Marlow Bottom, Buckinghamshire, also won the coxed four gold in Los Angeles in 1984 and the coxless pair gold in Seoul in 1988, Barcelona in 1992 and Atlanta in 1996.
Honours List
When Sir Steve returned to his home town after Sydney he was greeted by 30,000 well-wishers who lined the streets.
The public also voted him BBC Sports Personality of the Year in 2000.
Knighted last month, he was awarded a CBE in the 1997 New Year's Honours List for services to rowing, and an MBE 10 years ago.
The Queen also featured pictures of his victory in Sydney in her Christmas message.