Every claim we assess carries the same two marks: how strong the evidence is, and which way it points. This is the method behind them, and the reason we sometimes say "we don't know."
"A study found" tells you almost nothing until you know what kind of study it was. A quick tour from anecdote to meta-analysis.
"Doubles your risk" and "raises it from 1 in 10,000 to 2 in 10,000" can describe the exact same finding. One sells papers; the other tells you what to do.
A scientific consensus is not a vote, and not a demand for silence. It is what remains standing after decades of people trying to knock it down.
The pipeline from a modest finding to a confident health myth is short, well-worn, and easy to spot once you know the stations it passes through.
It is one of the most confidently repeated claims in parenting. It is also one of the most thoroughly tested, and the tests do not support it.
The famous rule is everywhere. A clear scientific basis for it is not.
On a subject where much is contested, this one is not: across an enormous body of research, regular movement is among the best-supported things you can do for your health.