If they work by bioelectric impedence, no.
Hydration levels are important with these scales, and you have to enter body type, sex and height so it can do the calculation. The scale sends a very low electrical current through your body and measures the resistance it encounters. Since muscle contains lots of water and conducts electrical currents well and fat doesn't, the electrical signal the scale receives back will be representative of the amount of muscle you have on your body. Taking your height and weight into account means that signal can be turned into a bodyfat percentage figure. Be hyperhydrated, and they'll measure you lower. Dehydrated, and you'll read higher.