This study introduces a practical work activity that allows students to investigate the inhibitory effects of seed extracts on pancreatic lipase activity. The activity is related to the issue of the ongoing global obesity epidemic and involves the use of materials and chemicals readily available in high school laboratories. We show how the activity can help students understand how scientists can control the reaction rates of key enzymes involved in the digestion of dietary fat, to combat obesity. The activity also illustrates how instructional scaffolding can help students understand important procedures related to the design, measurement, and handling of data which are critical in ensuring success among students performing scientific investigations.