This invention relates to the combination of α-amylase inhibitors prepared from Phaseolus vulgaris with α-glucosidase inhibitors obtained from Salacia oblonga and other species. The α-amylase inhibitor is accompanied by a quantity of lectins that reduces the amount of glucose originating from the starches present in the diet, and considerably reduces the appetite after repeated administration. The combination with α-glucosidase inhibitors, such as extracts of Salacia or the thiosugars present in it, further reduce the blood glucose, acting synergically, and consequently reduce the synthesis of fats from carbohydrates.