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Low
Calorie Diet
Obesity affects up to one-fourth
of adult Americans, increasing risk of death from diseases
like diabetes, high blood pressure, and heart disease. Traditional
weight loss methods include low-calorie diets between 800
to 1,500 calories a day and regular exercise. An alternative
method sometimes considered for bringing about significant
short-term weight loss in moderately to severely obese people
is the very low-calorie diet (VLCD).
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What is a Very Low-Calorie Diet
(VLCD)?
VLCDs are commercially prepared formulas
of 800 calories or less that replace all usual food intake.
VLCDs are not the same as over-the-counter meal replacements,
which are meant to be substituted for one or two meals a
day. VLCDs, when used under proper medical supervision,
effectively produce significant short-term weight loss in
moderately to severely obese patients.
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Who Should Use a VLCD?
VLCDs are generally safe when used under
proper medical supervision in patients with a body mass
index (BMI) greater than 30. BMI is a mathematical formula
that takes into account both a person's height and weight.
To calculate BMI, a person's weight in kilograms is divided
by height in meters squared. Use of VLCDs in patients with
a BMI of 27 to 30 should be reserved for those who have
medical complications resulting from their obesity. VLCDs
are not recommended for pregnant women or breastfeeding
women. VLCDs are not appropriate for children or adolescents,
except in specialized treatment programs.
Very little information exists regarding
the usage of VLCDs in older individuals. Because individuals
over 50 already experience normal depletion of lean body
mass, use of a VLCD may not be warranted. Additionally,
persons over 50 may not tolerate the side effects associated
with VLCDs because of preexisting medical conditions or
need for other medications. Therefore, a physician, on a
case by case basis, must evaluate increased risks and potential
benefits of drastic weight loss in older individuals. Additionally,
people with significant medical problems or who are on medications
may be able to use a VLCD, but this too must be determined
on an individual basis by a physician.
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Health Benefits Associated With
a VLCD
A VLCD may allow a severely to moderately
obese patient 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 improve obesity-related medical conditions,
including diabetes, high blood pressure, and high cholesterol.
Combining a VLCD with behavioral therapy and exercise may
also increase weight loss and may slow weight regain. However,
VLCDs are no more effective than more modest dietary restrictions
in the long-term maintenance of reduced weight.
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Adverse Effects Associated With
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 seen with
VLCDs is gallstone formation. Gallstones, which often develop
in obese people, anyway, (especially women), are even more
common during rapid weight loss. Some research indicates
that rapid weight loss appears to decrease the gallbladder's
ability to contract bile. But, it is unclear whether VLCDs
directly cause gallstones or whether the amount of weight
loss is responsible for the formation of gallstones.
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Conclusion
For most obese individuals, obesity is
a long-term condition that requires a lifetime of attention
even after a formal weight loss treatment ends. Although
VLCDs are efficient for short-term weight loss, they are
no more effective than other dietary treatments in the long-term
maintenance of reduced weight. Therefore, obese patients
should be encouraged to commit to a long-term treatment
program that includes permanent lifestyle changes of healthier
eating, regular physical activity, and an improved outlook
about food because without a long-term commitment, their
body weights will drift back up the scale.
Endnote: This e-text is a modified version
of a previously published review article on very low-calorie
diets, appearing in the August 25, 1993, issue of the Journal
of the American Medical Association. Both the review article
and this e-text were developed with the advice of the National
Task Force on the Prevention and Treatment of Obesity, a
subcommittee of the National Digestive Diseases Advisory
Board.
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