Well...eating mostly processed food could be a factor....
Yes, as a function of being overweight mostly. Your medical age is a factor derived from height, weight and any medical conditions that fall outside a demographic "normal". It is arbitrary in that sense like having your BMI compared to an Ethiopian.
Anecdotally, I look at pictures on youtube for random events in the USA and see a lot, maybe >30% of the young people meeting the criteria for being obese.
But hasn’t this country been doing that for generations?