Many people are delusional - but that does not negate the fact that people's lifestyle and environment affects how they age (far more so than their genetics, which is now believed to account for only 20-25% of how we age), and people's biological age can be significantly younger than their calendar age, and it can also be significantly older, care of lifestyle factors within most people's control - such as how the eat, whether or not they smoke or drink alcohol excessively, and how active or sedentary they are.
I find it weird that it can be acknowledged that some of our peers, or some random of similar age as us we see on the news on tv, look a lot older than their age and us, but not acknowledge the reverse.
I am reading a book about the new science around ageing, called "Why We Die", written by the Nobel Prize winner Venki Ramakrishnan, who knows his way around cells... He writes:
"We all know that people age at different rates. Some people look old at fifty, while others are remarkably youthful into their eighties."
It's not just good genes, it's about epigenetics, and factors that switch genes on and off - and that is lifestyle, levels of stress and hardship, and to a degree environment (so, pollution, etc). I would also say, attitude.