Weight loss is due to a person burning more kilojoules, or energy, than he or she takes in.
What is going on in the body?
A loss of weight is due to one of three factors:
Weight loss may or may not be intended. Though many of us strive for and probably would benefit from weight loss, weight loss that is unintended is often a sign of serious illness.
- less kilojoules are consumed
- more kilojoules or energy are burned off during activity
- a person's basic metabolism at rest speeds up
What are the signs and symptoms of the condition?
Those who lose weight through exercise and eating a proper diet have little to worry about. If anything, the main symptom of this type of weight loss is that a person feels healthier.
Unintended weight loss is a cause for concern. In this setting, the doctor will want to know more information, such as:
What are the causes and risks of the condition?
- How much weight has been lost?
- When did the weight loss start?
- Has the person's appetite or thirst level changed?
- Has the person's diet changed?
- Has the person's activity level changed?
- Has there been a change in the person's bladder or bowel habits?
- Has the person's mood changed?
- What medications or drugs is the person taking?
- What other medical conditions does the person have?
- Are there any other symptoms, such as fever or weakness?
Weight loss has many different causes, including:
Other causes of weight loss are also possible. Sometimes a cause cannot be found.
- an increased level of activity, due to exercise or manual labour
- eating fewer kilojoules
- medications or drugs. Weight loss can occur in those who abuse or regularly use amphetamines, ephedrine, cocaine, heroin, or alcohol.
- hormone imbalances, such as an increased thyroid hormone level known as hyperthyroidism
- diabetes, a condition that results in high blood sugar levels
- digestive diseases, such as inflammatory bowel disease or peptic ulcers
- conditions that affect the ability of the intestines to absorb food and other nutrients
- infections, such as HIV, tuberculosis, or endocarditis, an infection of the valves in the heart
- tumours or cancer of any kind, such as bowel cancer, lung cancer, cancer of the pancreas, or leukaemia
- psychiatric conditions, such as depression, anorexia, or schizophrenia
- severe kidney, liver, or heart disease
What can be done to prevent the condition?
Those who are trying to lose weight are often encouraged to do so. The population in Australia is overweight on average, and most people could stand to lose a few pounds.
For unintended weight loss, prevention is related to the cause. Avoiding the drugs that cause weight loss could prevent those cases due to drugs. Practicing safer sex could prevent many cases due to HIV infection. Many cases of unintended weight loss cannot be prevented.
How is the condition diagnosed?
Diagnosis of the cause of weight loss starts with a history and a physical examination. This may be all that is needed to figure out the cause in some cases. In other cases, further tests are needed. Blood and urine tests are commonly done. These can help detect hormone imbalances, kidney and liver disease, diabetes, certain infections, and other conditions.
X-ray tests may be done, such as a chest x-ray to look for heart or lung disease. A special x-ray test, called a CT scan, can look for cancer of the pancreas or liver.
What are the long-term effects of the condition?
Intentional weight loss from a healthy diet and exercise decreases the risk of: The long-term effects of unintentional weight loss are related to the cause. Cancer, diabetes, HIV, and severe heart, liver, or kidney disease are common causes of death. Many people who abuse drugs have long-term effects related to social, legal, and psychological problems from the drug abuse.
What are the risks to others?
Weight loss is not contagious. If infection is the cause of unintended weight loss, however, the infection may be contagious, as in the case of HIV or tuberculosis.
What are the treatments for the condition?
Those who are trying to lose weight should first speak with their doctor. Most people are advised to:
For people who are severely overweight, medications or surgery may be advised as well.
- exercise at least three times a week for 45 minutes at a time, using an activity that increases the heart rate
- eat healthy, following the Australian Guide To Healthy Eating
- read the labels of the food they eat. People are often surprised when they learn the kilojoule and fat content of foods.
- keep a diary of the food eaten. This also makes people more aware of their kilojoule intake and reinforces healthy habits.
Treatment for unintended weight loss is directed at the cause. For example, a person with diabetes may need insulin injections or other medications to control his or her blood sugar levels. Someone who is abusing drugs may need to enter a rehabilitation program. An individual with an infection may need antibiotics. A person with cancer may need surgery, chemotherapy, or radiation therapy.
What are the side effects of the treatments?
Side effects depend on the treatment used for weight loss. Exercise that is too strenuous can result in injury. Medications may cause allergic reactions or stomach upset. Surgery carries a risk of bleeding, infection, and allergic reactions to anaesthesia.
What happens after treatment for the condition?
A person who loses weight from diet and exercise often feels healthier and happier. Someone with unintentional weight loss may be cured by treatment, such a person with depression. Others may die, such as those with advanced cancer, HIV, or severe liver disease.
How is the condition monitored?
Weight can be monitored at home and at every visit to the doctor. Further monitoring is related to the cause. For example, a person with diabetes needs frequent blood tests to monitor his or her blood sugar level.
Author: Adam Brochert, MD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 28/02/2005
Potential conflict of interest information for reviewers available on request