A visually healthier-appearing individual at chronological age 50 likely has a younger biological age than a less healthy-appearing individual of the same chronological age.

“so if you took two people who were 50 years old and looked at them and one had lots of muscle mass and great posture and you know looked like a physical specimen of health and the other one was sort of slumped over maybe uh morbidly obese you know you take the exact opposite of that um it's it's probably the case that the fitter person would look younger”