Very Low Calorie Diets
Obesity affects nearly one-third of adults in the United States,
increasing their risk for diabetes, high blood pressure, and heart
disease. Traditional weight loss methods include low-calorie diets
from 800 to 1,500 calories a day and regular physical activity.
Health care providers sometimes consider an alternative method for
bringing about significant short-term weight loss in patients who
are moderately to extremely obese: the very-low-calorie diet.
What is a very-low-calorie diet (VLCD)?
VLCDs are commercially prepared formulas of about 800 calories that
replace all usual food intake for several weeks or months. VLCDs
are not the same as over-the-counter meal replacements, which are
meant to substitute for one or two meals a day. VLCDs, when used
under proper medical supervision, effectively produce significant
short-term weight loss in patients who are moderately to extremely
Studies have shown that meal replacements at higher calorie levels
(800 1000 calories) produce weight loss similar to that seen
with much lower calorie levels, probably due to better compliance
with the diet. In addition, VLCDs are usually part of weight-loss
treatment programs that include other techniques such as behavioral
therapy, nutrition counseling, physical activity, and/or drug treatment.
Who should use a VLCD?
VLCDs are intended to produce rapid weight loss at the start of
a weight-loss program in patients with a body mass index (BMI) greater
than 30. BMI correlates significantly with total body fat content.
It is calculated by dividing weight in kilograms by height in meters
squared, or by dividing weight in pounds by height in inches squared
and multiplying by 703.
Use of VLCDs in patients with a BMI of 27 to 30 should be reserved
for those who have medical complications resulting from their overweight.
VLCDs are not recommended for pregnant or breastfeeding women. VLCDs
are not appropriate for children or adolescents, except in specialized
Very little information exists regarding the use of VLCDs in older
people. Because people over age 50 already experience normal 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 need for other medications.
Physicians must evaluate on a case-by-case basis the potential risks
and benefits of rapid weight loss in older individuals, as well
as in people with significant medical problems or who 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.
Adverse effects of a VLCD Many patients on a VLCD for 4 to 16 weeks
report minor side effects such as fatigue, constipation, nausea,
and diarrhea, but 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 anyway 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. The drug ursodiol
can prevent gallstone formation during rapid weight loss, but is
not often used for this purpose.
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 and physical activity may help increase weight
loss and slow weight regain. In the long term, however, VLCDs are
no more effective than more modest dietary restrictions.
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