Body weight is controlled by our genes and managed by a neuro-hormonal system, in particular by insulin and glucagon. The meristematic extract of Japanese white mulberry blocks the alpha-glucosidase and then the intestinal hydrolysis of polysaccharides, thereby reducing the glycaemic index of carbohydrates. The target of our research was to evaluate the adjuvant slimming effect of the extract of white Japanese mulberry in the dietetic treatment of some patients who are obese or overweight. 46 overweight people were enrolled and divided into two subgroups: the subjects of both subgroups were given an identical balanced diet of 1300 kcal: subjects of the subgroup alpha received 2400 mg of white Japanese mulberry extract, the subgroup b subjects receive placebo. Each subgroup was followed-up every 30 days at 30, 60 and 90 days of treatment. Both in the periodic inspections and in the final inspection measurements of body weight and waist circumference in all the subjects and thigh circumference in women only were repeated. All subjects repeated blood tests. In the subgroup alpha, weight loss was about 9 kg in 3 months, equal to approximately 10 percent of the initial weight, significantly higher than subgroup beta (P<0.0001); moreover, the plasma insulin and glucose curves of the volunteers in this subgroup at the end of the trial were lower than those performed at the time of enrolment. In the 20 women of the beta subgroup treated with only low-calorie diet and with placebo, weight reduction was globally of 3.2 kg, approximately equal to 3 percent of the initial weight; moreover, the blood glucose curves and the insulin curves showed a slight decline compared to baseline, but not so significantly as was the case for group alpha. Waist circumference and thigh circumference (in women) decreased in all participants, obviously more evidently in subjects who lost more kg. The extract of white Japanese mulberry may represent a reliable adjuvant therapy in the dietetic treatment of some patients who are obese or overweight.