Decreased Appetite and Unexplained Weight Loss in Men

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If you're a man who has noticed that your appetite has decreased or you've lost weight for no apparent reason, there are many potential causes. While some may resolve on their own, others might require additional treatment. Knowing what to look for can help you decide when to seek help.

Causes of Decreased Appetite

The first step in managing a diminished appetite is determining the cause. Consider whether any of these conditions or issues might be affecting your appetite or eating habits, and discuss them with your healthcare provider.

Emotional State

Appetite can decrease in times of emotional upset. This includes periods when you may feel depressed, bored, or anxious. A reduction in appetite can also be caused by stress and the effect that it has on the brain's frontal pole.

Illness or Infection

Developing an illness or infection can also lead to a decrease in appetite, either directly or due to feeling nauseous. Infections that are often associated with a reduced desire to eat include:

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

Medical Conditions

In some cases, loss of appetite may be caused by a physical health condition. Medical conditions that have been known to reduce one's appetite include:

  • Amyotrophic lateral sclerosis (ALS)
  • Appendicitis (26% of males have loss of appetite with appendicitis compared to 14.5% of females)
  • Congestive heart failure
  • Digestive disorders such as irritable bowel syndrome (IBS), Crohn's disease, celiac disease, and colitis
  • Gastroesophageal reflux disease (GERD), also known as acid reflux
  • Intestinal blockage
  • Some cancers

Nutrient Excess or Deficiency

If your blood doesn't have enough of the minerals it needs, your appetite may be reduced. One example of this is hypokalemia, or low potassium in the blood, which can be caused by severe diarrhea, vigorous exercise, or the use of diuretics.

Appetite can also decrease if you have too much of a specific mineral. If you have hypercalcemia—which is a condition in which there is too much calcium in the blood—you may notice a decrease in your desire to eat.

Allergies and Sinus Conditions

More than 50 million Americans have some type of allergy. Sometimes it's an allergy to something outdoors (such as trees, grass, or weed pollen). Other times, the person might be allergic to something indoors (mold, cat dander, or mites).

Allergies can trigger the sinuses to release more mucous. When this mucous drains into your stomach, it can make you feel nauseous and reduce your appetite.

Food Poisoning

If you get food poisoning, you may not want to eat for a bit. Your stomach will likely be upset, potentially making it hard to keep food down until it starts to feel better. This can take hours to days after eating an unsafe food.

Some studies have even connected certain insecticides with instigating a type of food poisoning, ultimately impacting appetite. While this is rare, choosing organic fruits and vegetables can help limit this risk.


Some medications are designed to suppress appetite. Others have appetite suppression as an additional, unintended side effect. Medicines that fall into the latter category include:

Illegal Drugs

Taking certain illicit drugs can also cause one's appetite to decline. Drugs that can potentially have this effect include hallucinogens, inhalants, and lysergic acid diethylamide (LSD).

Other Causes

There are a few additional factors that can potentially decrease a man's appetite. Among them are:

  • Acute pain
  • Migraine headaches
  • High alcohol intake, especially over long periods of time

Causes of Unexplained Weight Loss

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.

One potential explanation is that the intake of calories is insufficient and outstripped by the energy needs of the body. Dramatic weight loss can also be due to an inability to digest and absorb food properly.

Malabsorption is the term used to describe this 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 not sufficiently absorbed are fats (lipids); however, malabsorption can apply to nutrients like carbohydrates and proteins, minerals like iron and calcium, vitamins, and electrolytes like potassium and sodium.

Malabsorption can be caused by several factors, including:

  • Digestive enzyme problems
  • Drug abuse
  • Fever
  • Gallbladder problems
  • Hyperthyroidism
  • Parasitic infections
  • Small intestine problems
  • Some medications causing long-term diarrhea

When to Seek Help

If your loss of appetite is accompanied by depression, an eating disorder, and/or drug or alcohol use, talk to your doctor. Seeking help is also recommended if you have any other symptoms that are unexplained. This can help rule out a medical condition.

When weight loss reaches more than 10% of your starting weight over a short period of time (3 months, for example), medical attention is required to search for medical causes.

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By Jerry Kennard, PhD
Jerry Kennard, Ph.D., is a psychologist and associate fellow of the British Psychological Society.