Rapid Weight Loss – Methods, Side Effects, Dangers

With over two-thirds of the American population being obese, the demand for weight loss methods is ever growing. There are many ways to lose weight and while some can be safe, others can be dangerous or even deadly. The main problem with some of the more dangerous methods is that weight loss is too rapid. While this may seem desirable, rapid weight loss can be dangerous, even deadly, and usually does not last.

What is rapid weight loss?

Losing weight at a rate of 1 to 2 pounds (around 0.5kg to 1kg) per week is considered to be safe. Therefore losing weight at a faster rate is considered to be rapid. This can be relative as people who are morbidly obese may find weight loss at a much faster rate and this may still be safe. Bariatric (weight loss) surgery may be an exception where the weight loss may be much higher but is still considered safe.

However, it is important to note that on some relatively safe weight loss methods there may be an initial rate of weight loss that can exceed 2 pounds per week. This is usually short lived, lasting only a week or two. Then the rate of weight loss returns to a safe level of 1 to 2 pounds per week. This temporary increased rate is not considered to be a problem provided that it stabilizes a short while thereafter.

Methods of Rapid Weight Loss

Safe weight loss methods involve reducing the intake of food by 500 calories per day or exercising to burn the equivalent of 500 calories per day. Within a week this reduction of 3,500 calories will lead to weight loss of around 1 pound. Slightly higher calorie reduction may be advised for some people.

Read more about weight loss myths.

Although many methods, including supplements and diets, may claim to be able to achieve rapid weight loss there are very few that can actually do so. It is important to note that rapid weight loss is never desirable from a medical perspective due to the dangers.

However, there are instances where rapid weight loss may be considered necessary like in cases where surgery needs to be done but the body weight has to be reduced quickly. In these instances the rapid weight loss has to be monitored by a medical professional and should only involve a dietary approach.

Starvation Diets

These diets involve living off water with lemon juice or certain spices added to the water. There is no food intake while on the diet. Contrary to popular belief these diets are not effective in the long term. It may cause short term  weight loss but is usually not sustainable and often a person who persists on this type of diet will need medical attention within a few days to a week or two, rapidly bring the diet to an end.

Very Low Calorie Diets

These diets involve consuming a maximum of 800 calories per day. At this calorie level there is a high risk of nutritional deficiencies, side effects and complications. Therefore very low calorie diets (VLCDs) are only reserved for certain cases and has to be overseen by a medical professional. To maintain the calorie restriction, nutrition is usually administered in the form of carefully measured liquid shakes.

Drugs and Supplements

There are a number of pharmaceutical drugs and nutritional/herbal supplements that are used for weight loss. Some of these drugs have been thoroughly researched and are indicated for weight loss purposes. With supplements, the research is often scanty and at times claims are made on anecdotal evidence. Neither drugs nor supplements can cause rapid weight loss. Doses should never be exceeded. Always consult with a medical professional.

Read more about weight loss drugs.

Excessive Physical Activity

While most methods focus on reducing calorie intake, weight loss can also occur with burning the excess calories than what is needed from the daily diet. Long periods of very strenuous activity on a daily basis can also lead to weight loss but it is rarely used as a method for rapid weight loss. This type of activity is not recommended for a daily basis. It can lead to heart strain and even breakdown of muscles which can be potentially deadly.

Read more about medical weight loss.

Side Effects of Rapid Weight Loss

The common side effects of rapid weight loss includes fatigue, headaches, nausea, irritability, difficulty concentrating, weakness and dizziness. These side effects arises within days. Constipation, menstrual disturbances hair loss and loss of muscle mass arise within weeks.

There is an increased risk of the following:

  • Gallstones
  • Dehydration
  • Nutritional deficiencies and its complications.
  • Malnutrition
  • Hypoglycemia

Dangers of Rapid Weight Loss

Organ Strain and Failure

One of the main dangers of rapid weight loss is the strain on the heart. This may occur for a number of reasons. It can lead to heart attacks (myocardial infarction), irregular heartbeat (arrhythmia) and may also contribute to heart failure. Rapid weight loss may affect any organ apart from the heart. When dehydration is severe it can also affect the kidneys, brain and nerves.


Another danger with rapid weight loss is that common side effects like dizziness and weakness may impair the ability of a person to operate a motor vehicle or work with dangerous equipment. This can lead to accidents which may be deadly and even put others at risk. There is also a risk of loss of balance and falls which may in turn result in serious and sometimes even fatal injuries.

Weight Fluctuations

Rapid weight loss is not sustainable. It is often followed by weight gain and even weight gain beyond the original body weight. The sudden loss of weight and the subsequent weight gain can have adverse effects on the body. It may impair the metabolism, weaken the heart and blood vessels, affect bones and disrupt bowel habit. In the long term the rapid weight loss can affect life adversely.

Always consult with a medical professional before starting any weight loss program. Rapid weight loss is never advisable except in a select cases where the weight loss is being medically supervised. Choose a weight loss program that is sensible and weight loss is moderate.


  1. www.webmd.com/diet/guide/rapid-weight-loss
  2. www.mayoclinic.org/healthy-lifestyle/weight-loss/expert-answers/fast-weight-loss/faq-20058289

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