Although supplemented fasting is now established as an efficient means of achieving substantial weight reduction in massively obese persons, widespread application of this treatment is contingent on its successful adaptation to a large-scale outpatient regimen. Of 519 patients treated as outpatients, 78% lost a minimum of 18.2 kg during the course of treatment. The overall rate of weight loss was 1.5 kg/wk, with females averaging 1.3 kg/wk and males, 2.1 kg/wk. The majority of patients tolerated the regimen well and were able to continue normal daily activities without experiencing any serious side effects.