What are the big 3 for thinning hair?

Can you please elaborate on the "big 3" that are commonly associated with thinning hair? Are these products, treatments, or lifestyle factors? If they are products, what specific ingredients or mechanisms do they utilize to combat hair thinning? Additionally, are there any scientific studies or clinical trials that support their effectiveness in preventing or reversing hair loss? Understanding the "big 3" for thinning hair could help many individuals address this common concern.