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.
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.
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.
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.
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.
