Very Low Calorie Diets

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).

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.

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.

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.

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.

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.

SOURCE: NIH Publication No. 95-3894


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