In 2010, 954 members of the Dunedin Study were assessed on for their apparent age on a wide range of biological markers. All participants were aged 38 at the time.
Good News: Clearly from the study, you can greatly influence the rate at which you age, for good or (too often) for worse.
The participants in the study aged at very different rates. The biological age of the youngest small group was 30-31, and the biological age of a similar small group at the older end of the scale, was 57-59. (Chronological age 38.)
10 died in accidents
12 died from cancer, disease or genetic defects
8 committed suicide
When the participants were 38 they were tested using 18 biomarkers as follows.
The 18 Biological Markers
Blood Test Markers (9)
Glycated hemoglobin. (Tests the stability of blood sugars)
C-reactive protein. (Measure of inflammation)
High density lipoprotein. (HDL - That's the "good cholesterol.")
Lipoprotein(a) (Risk factor for CVD)
Total Cholesterol (Once considered a risk factor for CVD)
Triglycerides (Fatty acids in the blood)
White blood cell count ( A measure of your immune system)
Leukocyte telomere length (The caps that protect the ends of gene strings.)
Apolipoprotein B100/A1 ratio (Identifies small, dense LDL particles)
Kidney Function (2)
Urea nitrate. (Ability of the kidney to remove nitrogen)
Creatinine clearance. (Measure of kidney health)
Exercise Related (3)
Forced vital capacity ration. (FEV1/FVC)
Forced expiratory volume in one second. (FEV1)
Cardio-respiratory fitness. (VO2Max)
Physical Condition (4)
Blood Pressure
Periodontal disease. (Gum disease)
Waist-hip ratio
Body mass index
So MOST of the participants were biologically older than their 38 chronological years. Why is that? We might begin by questioning the dietary guidelines first issued in 1997. This is the basis of the New Zealand Guidelines which I believe are unhelpful.
We should also understand that we live in "prosperous times" and our diet is not typical of diets through history at all.
What then is normal aging like? I think we don't really know. But certainly it need not include all the obesity and lifestyle diseases we currently see.
Dunedin Multidisciplinary Health & Development Study originally had 1037 participants. There were 1007 remaining in 2010. 
What then is normal aging like?