https://www.radionz.co.nz/news/national/366950/modern-teens-less-fit-than-parents-at-same-age-study
The findings were part of the long-term University of Otago's Dunedin Study which has surveyed health for more than 40 years.
The Dunedin Multidisciplinary Health and Development Study compared the fitness of members of the study measured in 1986 and 1987 with the results of 343 of participants' 15-year-old children.
Heart rates of teenagers taken an exercise bike were worse than their parents at the same age.
Researcher Dr Helena McAnally said there was a difference between genders.
Girls were about 25 percent less fit than their mothers generation, and boys' fitness was about 15 percent lower than their parents.
Can't say I'm surprised to see this. Shame that there's no way to see one generation further back using the same metrics - I'd guess there may have already been a similar decline. Anecdote only - but I think supported by looking at old school photos and comparing - on average IMO a class photo of Form 5 from about 1972 - the average looks underweight or almost malnourished by today's standards.