Kilocalorie restrictive diets have been used for years to help overweight and obese persons to promote weight loss. According to Wim Saris in "Very Low-Calorie Diets and Sustained Weight Loss," very low-calorie diets, or VLCD, have been defined to contain 400 to 800 calories per day.
Protein
VLCDs are used to promote significant weight loss while maintaining adequate protein to prevent malnutrition as a result of the severe calorie and protein restriction. According to Saris, 50g of protein are used to maintain adequate lean body mass and prevent muscle loss while promoting weight loss. An accepted ratio of 1:3 or 25 percent to 75 percent of muscle loss to fat loss is seen in persons following a VLCD diet. As fewer calories are provided and body fat stores are used for energy, the body becomes more efficient at using eaten calories. The body disposes all of un-necessary body weight, including some muscle, in the process of losing weight. Saris states there isn't any other clinical evidence that supports the body losing more than 25 percent weight from muscle mass despite the calorie level used to promote weight loss.
Promoting Weight Loss
During the first two weeks of following a VLCD, the weight loss you will experience comes from fluid loss. The large fluid loss occurs because insulin levels are lowered and promote the loss of sodium through the kidneys, according to Saris. When insulin levels decrease, glucagon levels increase and cause a diuretic effect. Your body will also shift to using ketones (fat metabolites) for energy. The use of ketones increases sodium and potassium loss along with fluid. Once this stage of weight loss occurs, your body will start tapping more into body fat stores and will stabilize your fluids and electrolytes.
Carbs and Fats
The low calorie level of the VLCD limits the amount of calories that can be devoted to carbs and fats. Under the VLCD, 50g of carbs are provided to maintain brain function while your body produces a large amount of ketone bodies to supply energy, according to Saris. The low level of carbohydrate provides enough glucose to support ketosis and spare proteins being used for energy. Essential fatty acids are provided in the VLCD diet, but there isn't a minimum or maximum gram amount recommended.
Efficacy
VLCD produces weight loss as with any calorie-restrictive diet program. The difference with VLCD programs is that participants can expect 15 to 20 percent of their starting weight to be lost three to six months following the protocol. After completing a VLCD program, weight loss maintenance can range from 8 percent to 14 percent one to 2.5 years after the completion of the diet, according to Margaretha Haugen and colleagues in "Assessment of Very Low Calorie Diets."
Side Effects
Following a VLCD is not free of side effects. According to Saris, common side effects include dizziness, headaches, fatigue, cold intolerance, dry skin, hair loss and in females, menstrual irregularities. This is due to the restriction of calories and demand of energy production for exercise and daily living.
References
- "Very-Low-Calorie Diets and Sustained Weight Loss"; Wim H.M. Saris; Obesity Research; November 2001
- "Assessment of Very Low Calorie Diets"; Margaretha Haugen, Eline Birkeland, Jak Jervell and Mette Svendsen; Norwegian Scientific Committee for Food Safety; May 2009
