While you might lose weight quickly by limiting your intake to 900 calories a day, you can't get everything your body needs to stay healthy when following this type of very-low-calorie diet, or VLCD. VLCDs are not traditional diets with meal plans made of regular foods. Instead, these diets are prescribed by a doctor and made up of specially formulated meal replacements to help meet vitamin and mineral needs while keeping calories low. You'd be followed closely by a doctor for the duration of any VLCD, including a 900-calorie diet.
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Weight Loss on Only 900 Calories
A pound of fat contains 3,500 calories. Reducing your daily calorie intake by 500 may help you lose 1 pound in a week. While calorie needs vary greatly depending on age, gender and activity, men need 2,200 to 3,200 calories a day and women need 1,600 to 2,400 calories a day to maintain a healthy weight. Depending on where you fall in this range, restricting your daily intake to 900 calories a day may help you lose 1 1/2 to 5 pounds a week.
People losing weight at a rate greater than 2 pounds a week may be losing muscle tissue and water, along with the fat. These types of VLCDs are recommended for people who are extremely obese and need to lose weight quickly for health reasons. VLCDs are often short-term, lasting no longer than 12 weeks, and are meant to help initiate fast weight loss at the beginning of a long-term weight-loss plan.
The Plan Uses High-Protein Meal Replacements
Because it's difficult to get all the nutrients your body needs eating 900 calories worth of regular foods, very-low-calorie diets are primarily made up of low-calorie meal-replacement shakes, soups, bars and other packaged goods high in protein and fortified with all the essential nutrients. These aren't the same type of meal-replacement drinks found at your grocery store, though, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Those over-the-counter shakes are meant to be substituted for only one or two meals a day.
Protein is essential for VLCDs because it helps preserve muscle mass while you lose the fat, supports immune health and acts as a source of energy when carbs aren't available. Plus, emphasizing protein on a weight-loss diet may also help with hunger control. Your doctor can help you determine how much protein you need for good health and weight loss, but most very-low-calorie diets aim to provide 60 to 80 grams a day.
What to Eat on a VLCD
Although you may be limited to the meal-replacement products on your 900-calorie diet, some plans may allow you to include foods as well. Food options may be limited to lean sources of protein, such as poultry, seafood and veggie burgers, and low-calorie veggies, such as spinach, lettuce, cucumbers and peppers. To further limit calories, these foods should be prepared without any added fat or sauces. That means meats that are baked, boiled or broiled and raw or steamed veggies. While corn, peas, potatoes and winter squash normally make healthy veggie choices, they're usually restricted or eliminated when following a very-low-calorie diet to help keep overall calories under control. Fruit and fats such as oil, nuts and seeds are also restricted for the same reasons.
Although you might lose weight faster eating only 900 calories a day, there are some side effects and possible health risks. Common, although often temporary, complaints include fatigue, constipation, nausea and diarrhea. A more serious issue might include the formation of gallstones, which is linked to the rapid weight loss.
Unfortunately, weight regain is also a common side effect, according to the National Institute of Diabetes and Digestive and Kidney Diseases. You may be able to prevent or limit gains by getting the proper support after you've lost the weight through participation in a weight-maintenance program that includes exercise and a mindful approach to eating.