Answer:
BD's are generally the dimentional specs of the planet Jupiter. Once an object reaches the mass of Jupiter, increased size(mass) manifests size as increasing density, while diameter, circumpherence, radius, volume, ect. pretty much stay the same w/ increased mass. Only density increases, I believe. Also, I think an increasingly dense object is difined as a BD when it reaches about 30 Jupiter masses, & is capable of becoming a true star at about 60 JM's. I believe the resulting star would become a red dwarf. Thermonuclear pulses from its interior cause it to try to explode but gravity checks the blast. Stars(suns) increase size differently than brown dwarfs. Their dimentional size(diameter ect.) increases a lot greater than their mass does & their average density decreases dramatically. That's because a more massive star burns much faster, resulting in far more expansion.