Decreased Appetite and Unexplained Weight Loss

Decreased appetite in men often comes with weight loss and has many causes

Woman weighing herself at home. Credit: Quiet Noise Creative / Getty Images

A decrease in appetite is quite common during illness, such as when suffering from a bout of influenza or other relatively short-term illnesses. Nausea is also associated with decreased appetite.

Appetite can also decrease in times of emotional upset, depression, boredom or anxiety.

Generally when the illness or emotional problem is resolved, the appetite returns to normal. If a decreased appetite is persistent, is accompanied by other symptoms such as those listed below, or there is unexplained weight loss, medical attention should be sought.

Infections That Can Cause Decreased Appetite

Infection can lead to a decrease in appetite. Infections that are often associated with a loss of appetite include:

  • Respiratory infections that affect the lungs
  • Pneumonia
  • Influenza
  • Kidney infection, such as pyelonephritis
  • Hepatitis and conditions that cause liver inflammation

Other Causes for Decreased Appetite

Factors that can affect appetite are many and can vary greatly. Other causes can include:

  • Psychological issues such as stress, anxiety, depression, grief or eating disorders like anorexia
  • Stimulants, weight loss medications, and medications for for attention deficit and hyperactivity disorder (ADHD) like amphetamines (e.g., Adderall)
  • Illicit drugs like hallucinogenics, inhalants and LSD
  • Migraine headaches
  • Hypercalcemia, a condition in which there is too much calcium in the blood
  • Hypokalemia, a condition where there is too little potassium in the blood

When Should I Seek Help for Decreased Appetite?

If a loss of appetite is accompanied by chest pains, shortness of breath, sweating, blurred vision or confusion—the warning signs of a heart attack or stroke—seek medical attention immediately.

Also seek medical attention if any of the follow signs and symptoms accompanies decreased appetite:

  • Unable to eat or drink for more than 12 hours
  • A high fever above 103 degrees Fahrenheit (40 degrees celsius)
  • Severe headache
  • Extreme abdominal pain
  • Stiffness in the neck
  • Dehydration with symptoms including dizziness, increased thirst and low urine output

Weight Loss from Decreased Appetite

During periods of decreased appetite, weight loss can obviously occur, but there are occasions when weight loss is unexplained and may be unrelated to decreased appetite. 

When drastic weight loss reaches more than 10 percent of the starting weight over a short period of time (for example, 3 months), a search for medical causes should be undertaken, and medical attention is required. 

Typically, dramatic weight loss is due to an inability to digest and absorb food properly, or the intake of calories is insufficient and outstripped by the energy needs of the body.

Weight Loss from Malabsorption

Malabsorption is the term used to describe the inability of the body to absorb enough nutrients from the consumption of food and drink.

This can lead to malnutrition and unexplained weight loss.

The most common nutrients that are not sufficiently absorbed are fats (lipids); however malabsorption can apply to nutrients like carbohydrates, proteins, minerals like iron and calcium, vitamins and electrolytes like potassium and sodium.

Malabsorption can be caused by several factors, including:

  • Digestive enzyme problems
  • Gallbladder problems
  • Small intestine problems
  • Parasitic infections
  • Some medications causing long-term diarrhea
  • Hyperthyroidism creating an excessive energy demand
  • Fever
  • Cancer
  • Drug abuse

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