Each diet uses a different format to help you lose weight and improve your health. Diets that replace entire meals with prepackaged meals, bars or shakes are known as "complete meal replacement" diets. By contrast, "juice fasts" limit your food intake to fruit and vegetable juice for five to 10 days. Because each type of diet presents unique features and concerns, consulting your doctor is essential before beginning any type of diet that differs significantly from your current lifestyle.
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Complete meal replacement diets claim to reduce weight by providing prepared, appropriately proportioned meals. Steady, measured weight loss is the goal of meal replacement diets. By contrast, juicing fasts claim to improve your overall health by removing toxins from your body while providing numerous micronutrients and antioxidants. A juice fast lasting several days reduces your weight, but this is only a desirable byproduct, not the primary goal.
The length of a juice fast varies from five to 10 days. During this time, your food intake is strictly limited to the fresh juice of fruits, vegetables and herbs. Certain juice fasts allow eating a plain, starchy vegetable, such as sweet potato, once every other day. Comparatively, a meal replacement diet continues until you've reached your desired weight. Depending on the particular meal replacement diet, you can begin reintroducing your own food after a period of several weeks.
Juice Fasting Concerns
A juice fast infuses your body with vitamins and nutrients but offers few calories or protein. To function properly, your body needs a minimum of 1,200 to 1,500 calories daily, along with several dozen grams of protein. Without these vital nutrients, your muscles begin breaking down, reports Lona Sandon, spokeswoman for the American Dietetic Association. Additionally, the claim that juice fasting removes toxins from your body is unsubstantiated. Says Sacramento-based gastroenterologist Dr. Nasir Moloo, “Your body does a perfectly good job of getting rid of toxins on its own.”
Meal Replacement Concerns
Unless the diet restricts certain nutrients, such as carbohydrates, each meal in a meal replacement diet attempts to include all the nutrition of a healthy, balanced meal. This also means you’re consuming all the additives and preservatives required to condense a meal's worth of nutrition into a bar or shake. Sensitivity to specific additives, such as nitrates and benzoic acid, could cause adverse reactions, ranging from asthma to headaches, reports allergist Dr. Adrian Morris of London's Surrey Allergy Clinic.