Your doctor may recommend a clear liquid diet before or following surgery. Photo Credit: Lesyy/iStock/Getty Images A clear liquid diet includes foods that are liquid at room temperature. These foods are easily digested, leaving no undigested residue in your intestinal tract. You doctor might prescribe a clear liquid diet prior to medical tests or surgery. He might also recommend it as a short-term diet if you have certain digestive problems such as nausea, vomiting or diarrhea. A clear liquid diet is not adequate for the long term, as it does not provide the body with all the essential nutrients. Video of the Day