If you live in a large city, chances are good that one (or more) of your local hospitals has a "Weight Management Center" which offers medically supervised diet assistance. Adults that have been clinically diagnosed as "obese" can often enter such a program and begin a liquid protein diet that may last for 8 to 18 weeks.
The goal of such hospital-based diet programs is safe (but rapid) weight loss. Patients are then counseled to transition to a 1,500 to 1,800 calorie daily diet. Cardiovascular training (or resistance training) is almost always a part of such a program. If this might work for you, contact your local hospital or health-care professional for more information.