Parasites & Weight Loss

Parasites invade your stomach and intestines, causing gastrointestinal problems that can lead to weight loss. The symptoms of intestinal parasitic infections can easily be confused with the symptoms of other gastrointestinal illnesses in the early stages of the infection. A delay in identifying a parasite as the source of the illness can result in frequent diarrhea, vomiting and subsequent weight loss.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.


Parasites are small organisms that live inside your body. Parasites enter your body through your skin and mouth and can be acquired if you touch contaminated soil, come in close contact with an infected person or drink or swim in contaminated water. Two water-borne illnesses, giardia and cryptosporidium, cause a significant number of parasitic infections in the U.S. Giardia is estimated to cause 2 million infections in the U.S. annually, while cryptosporidium causes 300,000 infections annually, according to the Centers for Disease Control and Prevention.

Weight Loss

Parasites interfere with your body’s ability to absorb calories and nutrients by triggering diarrhea and vomiting. The giardia parasite attaches itself to the lining of the small intestine, sabotaging the body’s absorption of fats and carbohydrates from digested foods. Nausea, another common symptom of parasitic infections, can affect your desire to eat, worsening the problem. Chronic vomiting, diarrhea and nausea can also lead to dehydration, a condition that occurs if your body does not receive enough liquids and water.

Symptoms of dehydration include dry mouth, reduced urination, sunken eyes and fatigue. If you have a weak immune system, due to cancer, AIDS or other conditions that affect the immune system, you may be at increased risk of developing severe symptoms if you have a parasitic infection.

Children and Parasites

Young children may suffer more severe symptoms due to immature immune systems. Because young children weigh much less than adults, any weight loss can quickly affect a child’s overall health. Pregnant women and young children may be more susceptible to dehydration and reports that rapid loss of fluids from diarrhea may be especially life threatening to babies.


Doctors treat parasitic infections with antibiotics and medications that kill parasites. Treatment results in a decrease in vomiting or diarrhea, allowing you to once again absorb nutrients from the food you eat. Your doctor may recommend drinking clear liquids and adding semi-solid and low-fiber foods, such as toast, crackers, eggs and chicken, as your bowel movements return to normal. Severe infections may require hospitalization.


While it may seem like a good idea to take an over-the-counter antidiarrheal medication if you have diarrhea, taking the medication may prolong your illness if your infection is caused by a parasite. Using an antidiarrheal medication prevents your body from shedding the parasite and may worsen your condition.