CLIF BARS are great-tasting, convenient source of energy for any activity. With a mix of carbohydrates, protein, and fiber, CLIF BAR is. moderate glycemic index food. What does this mean? Basically, you'll benefit from. steady increase in blood sugar levels followed by. gradual decline (sustained energy!) Eat. CLIF BAR. to‹2 hours before. workout or race, and you'll avoid the sugar high and crash associated with refined ingredients and sweeteners.. CLIF BAR delivers the boost you need without unwanted crash and burn.