A very low-calorie diet (VLCD) is not just any diet that is low in calories. It is a special type of diet that replaces all of your meals with prepared formulas, often in the form of liquid shakes.
A VLCD may be used for a short time to promote quick weight loss among some people who are considered to be obese. The diet requires close care from your doctor and is usually combined with other ways to lose weight (see How is obesity treated? below).
This fact sheet will tell you more about the risks and benefits of this type of diet. Do not go on a VLCD on your own. If you need to lose weight, talk to your health care provider about the approaches that may work best for you.
Obesity is treated using one or more of these strategies:
- a diet low in calories
- increased physical activity
- behavior therapy
- prescription medications
- weight-loss surgery
What is a VLCD?
A VLCD is a special diet that provides up to 800 calories per day. VLCDs use commercial formulas, usually liquid shakes, soups, or bars, which replace all your regular meals. These formulas are not the same as the meal replacements you can find at grocerystores or pharmacies, which are meant to replace one or two meals a day.
Depending on a number of factors, healthy adults need different amounts of calories to meet their daily energy needs. A standard amount is about 2,000 calories. VLCDs provide far fewer calories than most people need to maintain a healthy weight. This type of diet is used to promote quick weight loss, often as a way to jump-start an obesity treatment program.
VLCD formulas are designed to provide all of the nutrients you need while helping you lose weight quickly. However, this type of diet should only be used for a short time—usually about 12 weeks.
Very low calorie diets allow those who are moderately to extremely obese to lose an average of 3-5 pounds per week. This rapid weight loss can result in improvement of medical complications of obesity such as diabetes and high blood pressure. The rapid weight loss can also be a strong motivating factor for those wishing to lose a large amount of weight. Side effects of the diet can include fatigue, mild nausea, constipation, or diarrhea and dizziness.
A low-calorie diet, even in people who are not obese, can lead to changes in metabolism and body chemistry that have been linked to better health and longer life, researchers are reporting.
The findings lend support to the theory that eating less, long known to prolong life in rats and mice, may do the same for people, by preventing heart disease, cancer, diabetes and other diseases, and by slowing aging.
The notion that going hungry could be the fountain of youth has captivated scientists and the public. Calorie restriction, the scientific name for a regimen high in nutrients but low in calories, is the subject of intense research, and some people have already begun trying it on their own.
Research results from the RFO program have been published in the medical literature and have documented weight loss ranging from 50 to 250 pounds, depending upon the patients’ initial weight. Eighty five percent of patients successfully achieved their weight loss goals, and three years later sixty percent of them had maintained all or most of their lost weight. Accompanying this weight loss, there were marked reductions in blood pressure, improvement of diabetes control, improvement of serum cholesterol and lipid levels, and greater psychological well-being.
What are the health benefits of a VLCD?
A VLCD may allow you to lose about 3 to 5 pounds per week. This may lead to an average total weight loss of 44 pounds over 12 weeks. Such a weight loss can rapidly improve medical conditions linked to obesity, 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 also includes lifestyle changes may 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.
What are the health risks of a VLCD?
Doctors must monitor all VLCD patients regularly—ideally every 2 weeks in the initial period of rapid weight loss—to be sure patients are not experiencing serious side effects.
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 gallstones. Gallstones, which often develop in people who are obese, especially women, may be even more commonly developed during rapid weight loss. Some medicines can prevent gallstones from forming during rapid weight loss. Your health care provider can determine if these medicines are appropriate for you. For more information, see the WIN fact sheet on dieting and gallstones, listed under Resources.
What Are the Other Drawbacks of Very Low-Calorie Diets?
To be healthy, you need a balance of foods from different food groups. It’s difficult to get good nutrition and feel satisfied on a very low-calorie diet. In addition, consuming as few as 800 calories daily may not give you the energy you need for daily living and regular physical activity, especially if you eat the same foods every day.
Talk to your doctor or dietitian to make sure you get the nutrients you need while on a very low-calorie diet.