I am guessing the thing is based on the results of this:
The Nord-Trøndelag Health Study (HUNT) is one of the world’s largest population studies with data from three health surveys; HUNT 1 (1984-86), HUNT 2 (1195-97) and HUNT 3 (2006-2008). With a large collection of health data and biological material, HUNT data is used by researchers in many varied fields. At CERG, we have in part used HUNT data to study the relationship between physical activity and cardiovascular disease, for example looking at VO2max as a predictor of future health.
Over 200,000 participants so a pretty big sample. It would appear that the age is based on an average person so a fitness age of 20 or whatever is not a massive deal considering most people do no exercise.
VO2 max estimates are based on this: http://www.ntnu.edu/cerg/fitness-numbers
Not total Bollocks, it just that showing mean figures will always throw up outliers that make the predictions look a bit stupid. Like bodybuilders and BMI.