One specific liquid diet doesn't exist. Many variations of a very-low-calorie diet that has you subsist on juice, clinically prepared nutritional drinks, smoothies, or concoctions of cayenne pepper and lemon juice for days, weeks or even months persist, however. Some of these diets are used by medical professionals to intervene in cases of morbid obesity; others are followed by Hollywood starlets seeking to slim down for a role; some are followed by people hoping for miracle weight loss. If you want to lose weight quickly using a liquid diet, educate yourself on the implications and risks before choosing one. Also, check with your physician -- some are simply not a good idea to follow unless you're under medical care. You can lose weight fast if you do follow one, but it may not be worth the long-term consequences.
About Liquid Diets
A liquid diet involves replacing all whole, solid food with juice, smoothies, soups, frozen bars or a combination of any or all of these products. A liquid diet usually results in quick weight loss, because you restrict calories severely when you cut out whole foods. Weight loss occurs when you eat fewer calories than you burn; you lose a pound when that deficit reaches 3,500 calories. The average person needs about 2,000 calories to maintain body weight. Most liquid diets contain 600 to 1,000 calories per day, meaning you are creating a large deficit -- essentially starving yourself -- and will inevitably lose weight.
Don't confuse a liquid weight-loss diet with an all-liquid diet that is prescribed before or after certain surgeries or medical procedures. These diets aren't designed to be low in calories, but to be gentler on the gut and easier to digest.
Losing Weight on Liquid Diets
In cases of extreme obesity, a physician may place a patient on a very-low-calorie liquid diet to help shed pounds quickly. This can avert an immediate medical consequence resulting from excess weight or prepare a patient for bariatric surgery. A patient typically loses 3 or more pounds per week, but is followed closely by the doctor to make sure no complications arise.
Many non-medical versions of liquid diets exist too. To lose weight quickly, proponents of liquid diets require you to stick primarily to vegetable juices or low-sugar liquids, and avoid solid food. You may choose to drink home-pressed or purchased juice for all meals. Other liquid diets may have you sip broth or smoothies instead of eating vegetables, fruits, lean protein and whole grains. These diets aren't usually developed by a dietitian or doctor, but simply reduce your calorie intake so you lose weight. You see faster results if you stick to the liquids only and don't snack to supplement.
Side Effects of Liquid Diets
Whether you're following a juice fast that's promoted as "cleansing" or a liquid diet that promises to help you drop 10 pounds quickly, you're essentially starving your body and denying it the whole foods it needs to survive. A juice fast risks overloading your body with carbohydrates and sugar while forcing it to burn your muscle mass for energy. You may lose weight quickly if you subsist on juice alone, but you risk nutritional deficiencies, loss of energy, quick muscle loss and nausea.
Even medically supervised very-low-calorie liquid diets can have serious consequences. Followers may develop liver inflammation, abdominal discomfort, diminished immunity, muscle loss, nutrient deficiencies, bad breath, headaches, dehydration, severe fatigue, gallstones and kidney stones.
Liquid Diet Deficiencies
A juice fast can provide you with generous phytonutrients, carbohydrates and vitamins -- but is missing essential fatty acids, which support a healthy brain, and protein, to support muscle. Medically supervised liquid diets require hospitalization or regular checkups to ensure complications are not developing; a very-low-calorie liquid diet should not be followed for more than 12 weeks, even in a medical setting. Most people do not need to follow a very low-calorie diet and should follow a whole foods low-calorie diet to lose weight.
Liquid diets also fail to teach you how to craft meals that will support any weight loss in the long term. At some point, you'll start to to eat whole foods again; if you don't have good, healthy habits in place, you could end up regaining any lost weight and possibly more when you return to old ways of eating.