Very Low-calorie Diets
- What is a very low-calorie diet?
- Who should use a VLCD?
- Health Benefits of a VLCD
- Adverse Effects of a VLCD
- Maintaining Weight Loss
What is a very low-calorie diet?
A very low-calorie diet (VLCD) is a doctor-supervised diet that typically uses commercially prepared formulas to promote rapid weight loss in patients who are obese. These formulas, usually liquid shakes or bars, replace all food intake for several weeks or months. VLCD formulas need to contain appropriate levels of vitamins and micronutrients to ensure that patients meet their nutritional requirements. Some physicians also prescribe very low-calorie diets made up almost entirely of lean protein foods, such as fish and chicken. People on a VLCD consume about 800 calories per day or less.
VLCD formulas are not the same as the meal replacements you can find at grocery stores or pharmacies, which are meant to subsitute for one or two meals a day. Over-the-counter meal replacements such as bars, entrees, or shakes should account for only part of one’s daily calories.
When used under proper medical supervision, VLCDs may produce significant short-term weight loss in patients who are moderately to extremely obese. VLCDs should be part of comprehensive weight-loss treatment programs that include behavioral therapy, nutrition counseling, physical activity, and/or drug treatment.
Who should use a VLCD?
VLCDs are designed to produce rapid weight loss at the start of a weight-loss program in patients with a body mass index (BMI) greater than 30 and significant comorbidities. BMI correlates significantly with total body fat content. It is calculated by dividing a person’s weight in pounds by height in inches squared and multiplied by 703.
Use of VLCDs in patients with a BMI of 27 to 30 should be reserved for those who have medical conditions due to overweight, such as high blood pressure. These diets are not appropriate for children or adolescents, except in specialized treatment programs.
Very little information exists regarding the use of VLCDs in older people. Because people over age 50 already experience depletion of lean body mass, use of a VLCD may not be warranted. Also, people over 50 may not tolerate the side effects associated with VLCDs because of preexisting medical conditions or the need for other medicines. Doctors must evaluate on a case-by-case basis the potential risks and benefits of rapid weight loss in older adults, as well as in patients who have significant medical problems or are on medications.
Health Benefits of a VLCD
A VLCD may allow a patient who is moderately to extremely obese to lose about 3 to 5 pounds per week, for an average total weight loss of 44 pounds over 12 weeks. Such a weight loss can rapidly improve obesity-related medical conditions, including diabetes, high blood pressure, and high cholesterol.
The rapid weight loss experienced by most people on a VLCD can be very motivating. Patients who participate in a VLCD program that includes lifestyle treatment typically lose about 15 to 25 percent of their initial weight during the first 3 to 6 months. They may maintain a 5-percent weight loss after 4 years if they adopt a healthy eating plan and physical activity habits.
Adverse Effects of a VLCD
Many patients on a VLCD for 4 to 16 weeks report minor side effects such as fatigue, constipation, nausea, or diarrhea. These conditions usually improve within a few weeks and rarely prevent patients from completing the program. The most common serious side effect is gallstone formation. Gallstones, which often develop in people who are obese, especially women, are even more common during rapid weight loss. Research indicates that rapid weight loss may increase cholesterol levels in the gallbladder and decrease its ability to contract and expel bile. Some medicines can prevent gallstone formation during rapid weight loss. Your health care provider can determine if these medicines are appropriate for you.
Maintaining Weight Loss
Studies show that the long-term results of VLCDs vary widely, but weight regain is common. Combining a VLCD with behavior therapy, physical activity, and active follow-up treatment may help increase weight loss and prevent weight regain.
In addition, VLCDs may be no more effective than less severe dietary restrictions in the long run. Studies have shown that following a diet of approximately 800 to 1,000 calories produces weight loss similar to that seen with VLCDs. This is probably due to participants’ better compliance with a less restrictive diet.
For most people who are obese, obesity is a long-term condition that requires a lifetime of attention even after formal weight-loss treatment ends. Therefore, health care providers should encourage patients who are obese to commit to permanent changes of healthier eating, regular physical activity, and an improved outlook about food.
*Endnote: This fact sheet is an updated, modified version of a previously published review article appearing in the August 25, 1993 issue of the Journal of the American Medical Association. Both the review article and this fact sheet were developed with the advice of the Clinical Obesity Research Panel, formerly known as the National Task Force on Prevention and Treatment of Obesity.