Fiber prevents constipation by adding bulk to stool and promoting regular bowel movements. It functions as a natural laxative by softening waste, making it easier to pass through the digestive system. Eating sufficient fiber from sources like fruits, vegetables, whole grains, and legumes helps increase stool weight and transit time in the intestines. Additionally, fiber's role in maintaining gut health supports a balanced gut microbiome, which is essential for digestive efficiency. Increasing fiber intake gradually and ensuring adequate hydration can further enhance its effectiveness in preventing and alleviating constipation.