Soup has a high water content, which can help you feel full. And, just like salad, it’s a good vehicle for vegetables (the fiber in vegetables also promotes feelings of fullness for few calories). Research backs this up. In one study, published in the journal Physiology & Behavior, people consumed the fewest calories on days when they ate soup rather than the same ingredients in solid form.
In another study, published in Appetite, people who started lunch with vegetable soup ended up eating 20 percent less than those who skipped the soup. Broth-based soups packed with veggies give you the biggest bang for your caloric buck. (For an extra weight-loss boost, try these Recipes for Soups to Rev Your Metabolism.)