Liquid Diet

"Are Liquid Diets Used for Medical Purposes?
People who are about to undergo certain surgical procedures, such as colonoscopy and sigmoidoscopy, which call for little or no food in the intestines, might need to go on a liquid diet for a day or two before the test. Sometimes patients are put on a liquid diet for a few days after surgery or during certain medical treatments until their digestive tract is fully functioning again and they can digest food normally. Medically necessary liquid diets often include clear liquids such as soup, fruit juice, and Jell-o.
People who are obese and need to have surgery (including bariatric weight loss surgery) will sometimes go on a liquid diet to get down to a safer weight before the procedure. This type of liquid diet is supervised by medical professionals.
Some research suggests that liquid diets might help people with certain health conditions. For example, there is evidence that patients with Crohn's disease, which causes inflammation in the gastrointestinal tract, can benefit from a high-calorie liquid diet. By giving the intestines a much-needed rest, a liquid diet can help suppress the symptoms of Crohn's disease.
How Can I Safely Get on a Liquid Diet?
First, talk to your doctor about whether a liquid diet is appropriate for you. Certain people -- namely pregnant or nursing women and people with insulin dependent diabetes -- should skip liquid diets entirely."