Obesity or fat deposits are treated with ultrasound. In one embodiment, a waveguide-based apparatus and method are disclosed for applying ultrasound to a treatment-subject for the purpose of providing treatment or therapy for obesity, fat-deposits, cosmetic benefit or other bodily therapy tasks. In another embodiment, a novel apparatus and method are disclosed for providing at least one such treatment or therapy using a liquid-based waveguide. In yet another embodiment, a wearable apparatus is disclosed that incorporates a waveguide of the invention. Any of the embodiments has application to hospital use, clinical use or home use, for example, and the place of use will likely be determined by which treatment mechanism is employed and at what power-level.