A nutritional supplement composition contains inhibitors of alpha-glucosidase and alpha-amylase substantially in the absence of lipase inhibitors. The composition can include touchi extract and phaseolamin as the alpha-glucosidase and alpha-amylase inhibitor, respectively. A method of limiting the absorption of carbohydrates contained in a foodstuff includes administering the nutritional supplement composition prior to consumption of the carbohydrates, and a method promoting weight loss in an individual includes administering the nutritional supplement composition to the individual over a period of days.