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 chosen by obese people who want to lose weight quickly. These diets are rarely recommended by health care providers. People on these diets should be followed closely by a 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.
People who lose weight very quickly are much more likely to regain the weight over time than people who lose weight slowly through less drastic diet changes and physical activity.
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 provider. Most experts DO NOT recommend using a VLCD for more than 12 weeks.
Low-Calorie Diet (LCD)
These diets usually allow about 1,000 to 1,200 calories a day for women and 1,200 to 1,600 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 1 pound (225 grams to 500 grams) 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 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.
Very low-calorie diet; VLCD; Low-calorie diet; LCD; Very low energy diet; Weight loss - rapid weight loss; Overweight - rapid weight loss; Obesity - rapid weight loss; Diet - rapid weight loss
Academy of Nutrition and Dietetics website. Staying away from fad diets. www.eatright.org/resource/health/weight-loss/fad-diets/staying-away-from-fad-diets. Updated January 2, 2017. Accessed July 9, 2018.
Cowley MA, Brown WA, Considine RV. Obesity: the problem and its management. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 26.
Parretti HM, Jebb SA, Johns DJ, Lewis AL, Christian-Brown AM, Aveyard P. Clinical effectiveness of very-low-energy diets in the management of weight loss: a systematic review and meta-analysis of randomized controlled trials. Obes Rev. 2016;17(3):225-234. PMID: 26775902 www.ncbi.nlm.nih.gov/pubmed/26775902.
Review Date 5/17/2018
Updated by: Brent Wisse, MD, board certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.