In America anyway, a diagnosis of anorexia is tied to BMI, so many people are under the illusion you can’t get it if overweight. Technically it becomes OSFED (other specified feeding or eating disorder) with an anorexic suptype (otherwise non specified eating disorder). This minces clinical hairs, though.
I’d still typically consider standard AN far more dangerous potentially, but the OSFED subtypes many people are unfamiliar with so they often go underdiagnosed. Most clinicians don’t treat eating disorders, never mind screen for them. It’s possible, in theory, for an OSFED disorder to be just as dangerous (if not more so) than the “big 3” EDs. They just don’t fit into other diagnostic criteria.