New Zealand teenagers aren't as fit and weigh more than their parents did at the same age - especially girls.
The University of Otago research looked at 15-year-olds across two generations and found a decline in physical fitness and an increase body weight, keeping with global trends.
"We know fitness in adolescent tracks into adulthood, and so these changes may have important long-term consequences for health and well-being," Helena McAnally, who contributed to the research, said.
The decline in fitness was particularly noticeable in females, while males were also less fit than their parents but by a smaller margin.
"It is well-recognised that girls become less physically active earlier in adolescence, and this may be why their fitness levels were so much lower," Dr McAnally said.
The study measured fitness using a cycle test, which was chosen as a more accurate method over a running test because cycling does not require you to carry your body weight.
It also means findings of reduced fitness are not likely to have been caused by an increase in body weight.
"The findings support many people's perceptions that young people are less active and fit than their previous generations," Professor Bob Hancox, the research leader, concluded.
"These trends are likely to result in an increased burden on health and society as a whole."
The findings were published in the New Zealand Medical Journal on Friday.