Food58: analysing the microbiome would only really make sense alongside a general medical ‘work-up’.So also consider lists of symptoms (even mild), signs (other health tests), risk factors for or diagnoses of medical conditions.
The average young person is more interested in how they feel now and look now than in twenty or forty years time. Heck many of us supposedly ‘mature’ adults are just the same!
Skin conditions (and hair/ nails), menstrual cycle/ fertility/ sexual activity, body fat and muscle distribution (ie. body shape), mental wellbeing (depression/ anxiety/ social), energy, asthma, sports performance ….
Link these sort of issues to diet and lifestyle and they often want to make healthier choices. That is based on working in healthcare not parenting teenagers BTW!