The study, called Built Environment and Active Transport to School (Beats), painted a worrying picture of today's teenagers spending long hours in front of screens and fewer hours exercising.
Of those surveyed 22.2% were overweight and 7.1% obese.
Research team leader Dr Sandy Mandic, of the School of Physical Education, speaking after a recent symposium, said the results, which mirrored trends elsewhere, had alarming implications if the situation did not improve.
''The biggest problem is these young people, with being overweight and obese at such a young age, they are much more likely to be overweight and obese and adults.
''We are going to see chronic diseases appearing ... at a younger and younger age.
''[This] is going to impose a huge burden on our healthcare system and the quality of life of those people and eventually we may even see consequences on the longevity of these people.''
Parents could make a difference by encouraging their teenagers to walk or cycle to school, but there were no simple solutions, with a multiple-sector and agency response needed.
''It's changing the culture of young people and changing social norms.''
In future, the study could provide a baseline to see if changes to Dunedin's built environment - for instance the installation of cycle lanes - result in changes in behaviour.
The symposium was told, on average, pupils were spending 5.6 hours in front of screens - which equates to a little under a quarter of each day and adds up to 85 days every year - with only 13.1% meeting screen time guidelines of fewer than 2 hours per day.
Only 16.5% were meeting physical activity guidelines (of an hour or more of moderate-to-vigorous physical activity each day) and 28.7% dietary guidelines for both fruit and vegetable intake (more than one a day).
Only 2.7% of those surveyed met all three guidelines.
The issue of ''active transport'' - essentially walking or cycling to school - formed a large part of both the study and the symposium.
Study co-ordinator Ashley Mountfort said of the 584 students who lived within a 30-minute walk from school 65.1% walked to school regularly, 25.99% walked occasionally and 9.1% never walked.
These rates could be bettered by improving traffic safety and school bag weight, which was a barrier to some children walking to school.
Lauren Keaney explained that in a study of 74 pupils given accelerometers, those who used ''active transport'' to get to school, recorded 19 minutes more physical activity than those who used motorised transport.
The next stage of the study involved surveying parents of secondary school age students and people willing to participate could contact the study's organisers at beats@otago.ac.nz.
The Beats study is a collaboration between Otago University, the Dunedin Secondary Schools' Partnership (involving all Dunedin high schools) and the Dunedin City Council.
The stats
Dunedin secondary pupils:
• 22.2% overweight.
• 7.1% obese.
• On average spend 5.6 hours in front of screens (not including smartphones).
• Only 13.1% meet screen time guidelines of fewer than 2 hours per day.
• Only 16.5% meet physical activity guidelines.
• Only 28.7% meet dietary guidelines for both fruit and vegetable intake (more than one a day).
