A liquid diet is used for body cleanses, extreme or moderate weight loss or before or after certain surgeries. It can mean either partial or full meal replacement by either clear or non-clear fluids. Liquid diets fall into two categories, either an ultra low calorie or meal replacement liquid diet. The ultra low calorie liquid diet is practiced under strict medical supervision only. This diet provides on an average about 500 – 800 calories daily. This is normally a short-term diet plan, and can be useful for those who have serious obesity problems and need to lose a lot of weight quickly.

By contrast, the meal replacement liquid diet can be used for slower, more stable weight-loss. It replaces one or two whole meals with nutritious liquids, often carefully formulated to be high in fiber, protein vitamins and minerals, and low in fat. Certain liquid diets also permit the consumption of solid food, although portion size is carefully regulated.

The origins of liquid diets date back centuries. Many religious ceremonies involve fasting, to focus on the mind, heighten concentration, while cleansing the body. In most cases, during the fast, consumption of liquid is allowed, which is similar to a liquid diet. Another ancient use was to treat the sick. Many ancient cultures served only broth to sick patients, to reduce the strain of digestion on the organs. Only recently, in the past few decades, have several medically monitored weight loss programs, such as Optifast, and commercially available weight loss programs, such as Slim Fast, become available.


  • Medical Procedures – It is generally accepted that, for certain medical procedures, it is necessary for patients to refrain from eating solid foods for at least 24 hours before the procedure. Most hospitals have prepared patient literature about the precise dietary restrictions to be followed. The liquid diet is done to clear out the digestive system and decrease the strain on the digestive organs. The tests that might require this include sigmoidoscopy, colonoscopy, MRI, and certain x-ray, or serious oral, stomach, bariatric, or bowel surgery.
  • Obesity – When a person is extremely obese, a physician may prescribe a medically monitored weight loss program that will usually involve replacing solid foods with a liquid substitute for a total of about 500 – 800 calories daily. After a number of weeks of rapid weight loss and frequent meetings with a physician, who monitors the health and progress of the patient, solid foods may be slowly reintroduced. The entire process is difficult and can pose health risks, and requires careful monitoring by a physician. The metabolism slows, as the body goes into starvation mode. With the resulting hunger, the person does not gain the desired healthy eating habits or learn about portion control. Usually, this sort of liquid diet is only prescribed when serious health risks, caused by obesity, outweigh any risks from the program.
  • Weight Loss – There are many commercially available liquid diets for weight loss and their acceptance depends upon the brand and its program. In general, for moderate, rather than extreme weight-loss, the liquid component will form only part of one’s daily nutrition, with solid food being eaten in one or two meals. Brands where the diets also include regular food, and advocate a daily caloric intake of at least 1200 calories, and some kind of exercise recommendations, like Slim Fast, are generally more accepted by the medical establishment than programs that are very low in calories and do not include exercise, such as the Hollywood Celebrity Miracle Diet.

Side effects

  • Diminished Nutrition – The person on liquid diet may get very little fiber, antioxidants, or other essential vitamins and minerals. This can lead a reduced resistance to disease. While some liquid diet products are fortified with vitamins and minerals, they are unlikely to meet all your nutritional needs long term. And once you stop the liquid diet, the challenge is still transitioning back to real food successfully.
  • Possible Organ Damage – Short-term liquid diets for use before or after a medical procedure carry few risks and are generally considered safe. Doctors normally give the patient prescribed guidelines to make sure the body is prepared for the procedure without any negative health effects. Longer fasts are unlikely to meet all your nutritional needs, and carry several risks including possible damage to the intestinal tract, impaired liver or kidney function, and hypoglycemia.
  • Immune System – Fasting also impairs the body’s immune system, which makes the body more vulnerable to communicable diseases such as influenza or streptococcus. Gaining fat is also a common risk of fasting because, though the body may use stores of fat during the fast, once the fast is over the body usually rebuilds these stores quickly.
  • Digestive Complications – Liquid diets may be used to treat certain digestive problems, such as diverticulitis, or inflamed pouches in the intestine. However, treatment is usually only for a few days, or until the infection clears. When continued for longer weeks, e.g. several weeks or longer, liquid diets can cause gallstones, nausea, fatigue, constipation, and diarrhea.

Liquid diets are used for fasting, cleansing, to prepare the body for a medical procedure and for rapid weight loss. If they are done for more than a few days, it is strongly that a liquid diet is done under the supervision of a dietician or doctor. Liquid diets are unlikely to provide the body with sufficient nutrition, so in the long term, can cause immune, digestive problems and possible organ damage. Meal replacement drinks can be an effective tool for dieting, especially when used in combination with solid food, to make sure that the body does not go into starvation mode. However, the nutritional aspect can vary in quality, so its’ best to buy one that comes highly recommended.