Apparatus and methods for treating obesity using chronic cervical vagal nerve stimulation (cVNS) of the left vagus trunk are disclosed. Four men and ten women, average age 46 years (SD.+-.10) were treated with output current typically 0.75 mA, pulse frequency 30 Hz and width 250 or 500 .mu.s, and duty cycle of 30 s power per five minutes. Mean intake weight was 91 kg (SD.+-.27, range 46 to 137 kg) with body mass index (BMI) 43 kg/m.sup.2 (SD.+-.5, range 18 to 49 kg/mn.sup.2). After 6-12 months, obese patients had marked weight loss while normal weights were maintained. Decrease in BMI was consistently proportional to initial BMI. Average weight loss at one year was 7 kg (SD.+-.3, range -6 to +24) with mean drop in BMI of 2 kg/m.sup.2 (SD.+-.3, range -2 to +8)k. All patients denied any major dieting or exercise.