Diseases that cause weight loss 
The reduction of body weight can be caused by a disease. 

Sometimes a patient may not know the disease that is causing weight loss because the signs and symptoms are not obvious.

The most common cause of unintentional weight loss is the consequence of:

Another cause may be reduced mobility that impedes or hinders the preparation and consumption of food. 
In case of sudden weight loss, it is necessary to go to the doctor as soon as possible, because the reason can be a serious illness.

Cachexia is a medical term to indicate severe weight loss and muscle loss that occurs in the following cases:


Causes of unintentional or pathological weight loss

The diseases listed below are some of the most common causes of weight loss. Not all symptoms or clinical signs listed may be evident. There are other causes that should be considered in cases of unexplained weight loss.

Weight loss is a common feature of most types of addiction, including:

  • Alcoholism ,
  • Abuse of narcotic medications.

The nicotine can also cause a decrease in appetite.

A malignant tumor may not be seen until the late stages of the disease. 
The fatigue ,  and unexplained weight loss may be the only signs in the early stages. 
Slimming occurs even when eating as before, because the cancer cells consume a lot of energy to grow. 
A tumor can also cause symptoms such as:

Be the diabetes mellitus that diabetes insipidus can cause a loss of weight. 
It can occur with other symptoms, for example:

Metformin is a medicine used to treat diabetes;  if given regularly, may cause a slight reduction in body weight.

Eating Disorders
Weight loss is a common feature in most eating disorders , especially in anorexia nervosa . 
This cause should be suspected in adolescents and young people, especially in women. 
It can occur along with other behaviors, for example:

  • Avoid food;
  • Compulsive food;
  • Vomiting ;
  • Lack of selfesteem;
  • Obsession with body weight or shape.

Gastrointestinal infections
May be due to viral, fungal, bacterial or parasitic infectious agents. The intestinal parasites humans can remain undetected for long periods of time. 
The other symptoms that cause gastroenteritis are:

Gallbladder Problems
Gallstones are cholesterol deposits that form in the gallbladder when the liver produces an excess of:

  • Cholesterol,
  • Bile.

Most people who develop gallstones do not have symptoms, but  when the biliary tract is blocked, the symptoms are:

The infection with the human immunodeficiency virus ( HIV ) or the onset of AIDScan cause weight loss and cachexia visible in the latter stages. The other symptoms of the disease are:

  • Night sweats ;
  • Fever;
  • Fatigue;
  • Repeated infections, such as colds  or seasonal flu .

Also called thyrotoxicosis, weight loss is due to an overactive thyroid and high levels of thyroid hormones that increase the basal metabolic rate. Other symptoms of hyperthyroidism include:

  • Heat intolerance;
  • Excessive or abnormal sweating;
  • Tremor;
  • Leading eyes (exophthalmos);
  • Fatigue ;
  • Irritability;
  • Anxiety ;
  • Insomnia .

Mental illnesses
These include:

  • Depression ,
  • Bipolar disorder ,
  • Schizophrenia ,
  • Dementia .

Mental illnesses can cause the following symptoms:

  • Lack of self – esteem ,
  • Delirium,
  • Cognitive abilities or altered perception,
  • Irrational behavior,
  • Abnormal patterns of behavior in daily activities and social interaction,
  • Insufficient or excessive appetite.

Weight loss can be caused by an active infection with Mycobacterium tuberculosis. 
The TB primarily affects the lungs but can also affect other organs without lung involvement.

Enter the symptoms are:

Weight loss can be caused by mental or emotional stress due to lack of appetite and reduced food intake. 
Usually the person is worried about an activity or a past event, but also the hormonal causes (stress hormones) may be involved in the lack of appetite. 
They can cause a temporary loss of appetite and weight:

  • Work stress ,
  • Financial worries,
  • Recent traumatic events (such as death or divorce),
  • Post-traumatic stress disorder (war, criminal acts).

It can occur with other symptoms, for example:

  • Irritability;
  • Depression;
  • Panic attacks ;
  • Insomnia ;
  • Nightmares.


Weight loss and menstrual cycle

Overweight women are not the only ones who can have problems with the  menstrual cycle . 
delay of the menstrual cycle that can last a few months can occur in:

  • Women with eating disorders that cause extreme weight loss (eg, anorexia nervosa ),
  • Women with low weight.

Women with low body fat may have fewer menstrual cycles. 
A drastic diet can cause blockage of ovulation. 
Hunger, extreme exercise and stress can affect the activity of the hypothalamus . 
Some women are so underweight that the body stops producing the hormones. In addition, lack of fat does not allow cells to convert cholesterol to estrogen.


Side Effects of Very Fast Weight Loss

Muscle Loss
An important side effect of sudden weight loss is the reduction of lean muscle tissue. Eating an insufficient amount of calories leads to a lack of energy for the body.

In the case of fasting , after the first 24-48 hours, the body decomposes fats and creates ketone bodies:

  • Acetoacetic acid,
  • Beta-hydroxybutyric acid,
  • Acetone.

Many people worry because they believe that fasting causes a loss of lean body mass; instead the opposite happens because, when the body runs out of glucose, it uses fat. 
The loss of muscle mass can occur in case of low calorie diet because the body does not produce ketone bodies, so it can also use muscle proteins.

Feeling Cold
A temporary but unpleasant side effect of very rapid weight loss is the chills and the feeling of cold. 
Fat insulates the body and prevents loss of body heat. 
Rapid weight loss removes a portion of that insulation. 
On the contrary, some overweight people sweat excessively.

Hair Loss
Another side effect of rapid short term weight loss is hair loss. 
It usually occurs as a result of insufficient protein intake; the body sacrifices some hair-derived proteins to support other important functions of the body. 
The good news is that when you turn to a correct diet with an adequate amount of protein, your hair grows again.

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