We all know how important diet and exercise are in the quest for a lean physique, but did you know laughing can help too? You can burn up to 40 more calories a day by just laughing for 15 minutes. Laughing increases your heart rate by up to 20 percent, which increases your metabolism. By the way, laughing also has been shown to bolster the immune system by increasing the production of natural killer cells. So if you want to be healthier, don’t just eat that banana—throw the peel on the floor and wait.