Not every food is created equally and not every calorie is burned equally in your body. According to Dr. Neal Barnard, author of Foods That Cause You to Lose Weight: The Negative Calorie Effect, there are a variety of foods that create a negative-calorie effect, which improves your metabolism and helps you lose weight effectively. These foods are usually plant-derived foods that are high in water content and rich in fiber: grains, legumes, vegetables, and fruits, except for fatty fruits like avocados and olives. Since your body takes a longer time to burn off fibrous foods, your metabolism continues to stay revved up, giving you a jumpstart to your weight loss. Get started by adding these 20 foods into your recipe rotation.