The board's healthy eating, healthy action manager, Rosie Gordon, said staff who led active, healthy lives were in a better position to promote healthy lifestyles to patients.
A staff survey in 2007 found 73% of respondents thought it was important to be good role models for healthy eating and activity, but 20% of respondents only got one to three hours of exercise a week.
The fitness classes would hopefully also promote greater use of the board's well-equipped staff gym, she said.
"When I first started [working here], I was told it was there, but didn't know where it was for ages."
It costs staff $45 a year to use the gym.
The idea of having lunchtime lectures on topics they could apply to their own lives or use clinically with patients had come from a group of motivated staff, who acted as "staff champions for healthy eating, healthy action".
The group came from a wide range of staff, including nurses, occupational therapists and Public Health South staff.
The first lecture, on how to understand labels on food packets, and to be held today, is from one of the board's dietitians. Other suggested topics have been how to get started on a fitness programme and how to lose weight.
The lectures will be held monthly and the fitness classes will be held three times a week at Dunedin Hospital and once a week at Waikari Hospital, at a cost of $5 each.
About 15 staff had attended a couple of free fitness classes two weeks ago, and Ms Gordon hoped once word got around the new classes would be popular.
Last October, the board launched its nutrition and physical activity policy to encourage healthy lifestyle choices among staff.
