Definition and Overview

Weight loss is defined as the reduction in body mass and body fat. However, extreme cases may also involve loss of protein, lean mass, and other substrates in the body. It may either be intentional, like when you go on a diet or unintentional, when it is secondary to a disease such as infection or cancer.


Multiple factors come into play when it comes to losing weight. The basic principle involved is that the body weight is influenced by the amount of energy that we use in our daily activities and the amount of energy found in the food that we eat. A person whose weight does not change is most likely burning the same number of calories as he is taking in. The excess calories taken in are stored in the body as fat. Thus, for people who want to lose weight, they can either decrease the amount of food intake or increase the amount of energy they expend in their physical activities.

Intentional weight loss is usually carried out to improve a person’s health and promote fitness. People who are obese or overweight can benefit significantly with this form of weight loss, as health risks can be reduced and diseases, such as hypertension and diabetes, can be prevented. Patients who intentionally want to lose weight can do so with lifestyle modification strategies, mainly a combination of a low-calorie diet and increased exercise or activity. Other techniques to lose weight include the use of certain medications. For patients who are severely obese, bariatric surgery can be performed to decrease the size of the stomach.

On the other hand, unintentional weight loss could be a manifestation of a number of medical conditions. Illnesses tend to increase the metabolic demands of the body, even in the resting state. At the same time, diseases can lead to a loss of appetite or an inability to eat, resulting in decreased caloric intake. Aside from these, certain diseases that affect the gastrointestinal system can result in problems in digestion or absorption of nutrients. In addition, excessive losses of calories and nutrients may also occur, especially in patients with chronic diarrhea or vomiting.

Some examples of diseases that cause weight loss include malnutrition, chronic infection such as tuberculosis and HIV, long-standing illnesses such as hyperthyroidism or Parkinson’s disease, different forms of cancer, and chronic depression. Digestive system conditions leading to weight loss include parasitic infections resulting in chronic [diarrhea, inflammatory bowel syndrome or chronic pancreatitis, among others. Stomas or enterocutaneous fistulae can also lead to weight loss due to excessive loss of nutrients. Some medications, specifically diabetes and chemotherapeutic drugs, may also induce weight loss.

Continued and progressive weight loss can result in medical condition known as wasting or cachexia. This state is associated with poor outcomes. With this condition, patients can lose weight even when they are receiving enough calories. Severe weight loss can affect various systems of the body and could result in devastating consequences, including impaired healing and immune response, weakened muscle strength, kidney dysfunction, and even death.

Key Symptoms

Weight loss can be alarming if it happens too fast. If you want to lose weight, it is best to lose an average of 1 kg a week. Otherwise, you might end up losing lean muscle instead of body fat. People who lose more than 5 to 10% of their usual body weight in a span of a year or less for no reason at all, are advised to seek medical attention. It is also recommended to consult a physician if you experience other symptoms, such as chronic cough or diarrhea, together with weight loss.

Symptoms of unintentional weight loss are:

  • Abdominal discomfort or pain
  • Fever
  • Loss of appetite
  • Constipation
  • Diarrhea
  • Physically smaller stature

Who to See and Types of Treatments Available

A general medical practitioner or family doctor can evaluate the cause of your weight loss. You will be asked about your medical history and eating habits. Your physician can also elicit symptoms that you may not have noticed but could be related to your condition. A complete physical examination and as well as laboratory tests will be ordered to determine the exact causes.

Treatment will depend on the cause of the weight loss. Patients with associated medical conditions are referred to medical or surgical specialists to manage the disease. Your health care provider may also need to work with a nutritionist or dietician in order to check if you are receiving adequate nutrition. Typically, an up building diet rich in protein and nutrients is recommended for patients in order to gain weight.


  • Weight Loss Institute – SMM Health.
  • National Weight Control Registry.
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