Ask most health systems what "first-line treatment" means and physical activity rarely comes up first — a prescription usually does. The evidence points the other way for a long list of conditions.
Roughly 150 minutes a week of moderate activity is associated with meaningfully lower rates of cardiovascular disease, type 2 diabetes and several cancers — and the relationship keeps improving with more activity up to a point, the kind of clean dose-response curve a single drug rarely produces across that many conditions at once. It also arrives with side effects that run the opposite direction of most medication: better sleep, better mood, more strength, instead of a list of things to watch out for.
The gap is rarely awareness — most people already know movement helps. It is that a first-line strategy needs the same things a prescription gets by default: a clear starting dose, a plan for when life gets in the way, and someone checking back in. A routine built around one or two forms of movement someone will actually keep doing beats an ambitious plan abandoned in three weeks, and that is the design problem worth solving before adding anything else.