The phrase "increased diameter" means that something has become larger in size, specifically the distance across its center or widest point. Full definition
By increasing the diameter of blood vessels, the pressure against the walls of these blood vessels is effectively reduced. (mypetneedsthat.com)
In dogs, many of these foods are size specific, based on findings from one study where increasing the diameter of kibble by 50 % led to a 42 % reduction in tartar. (activ4pets.com)
In one study, increasing the diameter of kibble by 50 % led to a 42 % reduction in tartar. (pets.webmd.com)