Rapid weight loss diet is a type of diet in which you lose more than 2 pounds (1 kilogram, kg) a week over several weeks. To lose weight this quickly you eat very few calories.
How it Works
These diets are most often for obese people who need to lose weight quickly because of a health problem. People on these diets should be followed closely by a health care provider. Rapid weight loss is not safe for most people to do on their own.
These diets are only to be used for a short time and are not recommended for more than several weeks. The types of rapid weight loss diets are described below.
Very Low-calorie Diet (VLCD)
On a VLCD, you may have as few as 800 calories a day and may lose up to 3 to 5 pounds (1.5 to 2 kg) week. Most VLCDs use meal replacements, such as formulas, soups, shakes, and bars instead of regular meals. This helps ensure that you get all of the nutrients you need each day.
A VLCD is only recommended for adults who are obese and need to lose weight for health reasons. These diets are often used before weight-loss surgery. You should only use a VLCD with the help of your health care provider. Most experts DO NOT recommend using a VLCD for more than 12 weeks.
Low-calorie Diet (LCD)
These diets usually allow about 1000 to 1200 calories a day for women and 1200 to 1600 calories a day for men. An LCD is a better choice than a VLCD for most people who want to lose weight quickly. But you should still be supervised by a provider. You will not lose weight as fast with an LCD, but you can lose just as much weight with a VLCD.
An LCD may use a mix of meal replacements and regular food. This makes it easier to follow than a VLCD.
Some fad diets also severely limit calories to achieve rapid weight loss. In many cases, these diets are not safe. Once you stop the diet, you are at risk for regaining the weight if you return to your old eating habits. For most people, it is safest to choose a diet in which you lose a 1/2 pound to 2 pounds (225 grams to 1 kg) a week.
The Role of Exercise
Rapid weight loss is more about cutting calories than exercising. Talk with your provider about what type of exercise you should do while you are on this type of diet. Your provider may suggest waiting until you are on a more long-term diet to start exercising.
Rapid weight loss diet is usually for people who have health problems because of obesity. For these people, losing a lot of weight quickly can help improve:
- High cholesterol
- High blood pressure
Possible Health Concerns
You should only follow one of these diets with the help of your provider. Losing more than one 1 or 2 pounds (0.5 to 1 kg) a week is not safe for most people. It can cause you to lose muscle, water, and bone density. Rapid weight loss can also cause some side effects including:
People who lose weight quickly are also more likely to gain back the weight quickly. This can lead to other health problems.
In general, a rapid weight loss diet is not safe for children. It may also not be safe for teens, pregnant women or older adults unless a provider recommends it.
If you have a health condition, it is a good idea to talk with your provider before starting this or any diet plan to lose weight.
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Review Date 4/24/2016
Updated by: Emily Wax, RD, The Brooklyn Hospital Center, Brooklyn, NY. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.