Action. We have to increase our activity and consume less calories to see significant changes in our bodies. What makes the Herbalife 21 day challenge meal plan so effective? Let's cover some of this below.Also, the recommended herbalife 21 day challenge meal plan is to drink 3 Herbalife shakes coupled with water each day. In addition, you want to drink your shakes mixed with 250ml of semi-skimmed milk per shake.Drink three Herbalife shakes each day for 3 weeks