Part GQ, part IMHO.
I am thinking mostly of nutrition, but my question applies to fitness/exercise as well.
The format is this: “In a long-term study that followed x# of individuals for y# of years, results suggested that people who ______ had a greatly increased rate of ______”
Some of these studies extend over 5, 10, 15 years. My question is, how does natural human variability affect those studies, given that I suspect very few people maintain the same habits across decades?
I mean, my nutritional habits vary greatly over time according to my finances, my age, my emotional well-being, and my understanding of current nutritional theory.
Are the long-term values averaged? Would my years of 1 veg serving/day in my thirties be averaged against the 7 veg servings/day I eat now, and be treated as an overall intake of 4 veg serving per day? I used to think it was fine to drink a quart of fruit juice every day; now I hardly touch the stuff. I’m not the only one now eating more fish, fewer potatoes.
For exercise, does anyone really maintain a constant rate/intensity over the course of years, or wouldn’t a lot of people get off track for months at a time after the birth of a child, a change in their hours/place of employment, having to care for aging family members, bad breakups, injuries?
The IMHO component to my question is: how discouraged should I be when I read these studies, thinking, wow, I don’t have a decade of (whatever the research is looking at), I wonder if it is even worth making changes? But I think I could better assess that for myself if I understood how the data in those studies gets analyzed, and there should be some protocol for that.