A textile machine receives a plurality of yarns from respective feeders, each provided with a control unit that calculates, for each garment produced, the amount of yarn consumed (YCmeas) and compares it with a reference consumption value (YCref). If the difference exceeds a preset limit value (% max) that indicates an anomaly, then an alarm is generated. Periodically, the control unit calculates an average consumption value (YCmed) on the basis of a preset number (Nmed) of already-finished garments, and compares it with the reference consumption value (YCref). If the difference exceeds a preset threshold value (% maxmed), then the reference consumption value (Yref) is set to the average consumption value (Ymed).