Can Intestinal Worms Cause Weight Gain?

Intestinal parasites are mainly associated with weight loss. There is even an old myth regarding the tapeworm diet. Supposedly, if a person were to ingest a tapeworm, the parasite would consume calories from the person’s meals, so they would not gain weight and would burn the pounds they have. While weight loss indeed can be a sign of a parasitic invasion (along with other symptoms), intestinal worms can cause weight gain as well.

What are Intestinal Worms?

Intestinal worms are a common type of parasitic infection. A parasite is an organism that lives off the host’s body. Although they usually live in one’s intestines (as the name suggests), they can spread to other parts of the body, including the brain.

There are several main types of intestinal worms.


Roundworms, or nematodes, belong to a large group called Nematoda. Not all roundworms are parasitic: for example, there are free-living species that play a vital role in marine and freshwater environments.

There are, however, many nematodes that parasitize humans, such as:

  • Ascarids—most common human intestinal parasite. An infection with ascarids is called ascariasis.
  • Hookworms—blood-feeding parasites. In humans, hookworm infections are caused by the Necator and Ancylostoma parasitic genera.
  • Pinworms, or threadworms, are parasites of the species Enterobius vermicularis. Pinworm infection is also called enterobiasis. It rarely develops extraintestinal growth but can affect the female reproductive system. There was also a case of spleen abscess.


A tapeworm, or cestode, belongs to a group of flatworms that includes over 5,000 species worldwide. Their size can range from 1 mm to more than 15 m. There are three most common kinds of tapeworms that affect humans and animals:

  • Taenia saginata, or beef tapeworm, uses cattle as temporary carriers. When a human consumes contaminated meat (beef, mostly), the parasite enters the human body and makes it its permanent host.
  • Taenia solium, or pork tapeworm, affects people who eat unprocessed pork meat.
  • Dibothriocephalus latus, fish tapeworm, infests humans and animals that eat fish.

Infections caused by the invasion of pork and beef tapeworms are called taeniasis. Untreated T. solium taeniasis may cause cysticercosis. It is a condition that occurs when the parasite’s larvae travel into other parts of the body (muscle, brain, eyes, skin, etc.) and form cysts there. Cysts cause lots of complications, including vision loss, headaches, and seizures, and even can be lethal.

How do intestinal worms enter the body?

A person can catch worms from contacting and/or ingesting contaminated:

  • soil;
  • water;
  • foods (such as freshwater fish, pork, beef).

Worms and their eggs may also infect other parts of the person’s environment, such as kids’ toys, bed linen, etc. For example, pinworms may remain infectious while being indoors for 2-3 weeks.


Generally, parasitic invasions do not cause too many health issues. It is an evolutionary mechanism: if the host suffers too much from the parasite, they will more likely notice it and try to get rid of it.

Nevertheless, there still can be signs that someone has been infected with intestinal worms:

  • constipation from the intestinal blockage;
  • diarrhea and other digestive disorders;
  • gas, bloated belly;
  • pain and tenderness in the abdomen;
  • fatigue (caused by malabsorption of nutrients);
  • sudden changes in weight and appetite.

How worms cause weight gain?

So, how exactly do parasites cause weight gain? Firstly, one should note that a swollen abdomen is not necessarily caused by parasites and belly fat. Intestinal parasites can sometimes cause a condition known as ascites—a pathologic build-up of the fluid in the abdominal area. It leads to rapid weight gain and enlarges one’s tummy but there is no fat involved.

In other cases, intestinal parasites and weight gain can be connected through changes that the parasites incur.

Nutrient Absorption

If the patient is deprived of nutrients due to parasitic infections, they are expected to lose weight, right? Quite often, this is exactly what happens. However, deficiency in nutrients can cause certain cravings that people may try to mitigate with snacks and junk food. Lacking specific nutrients may also affect one’s mental health which leads to dropping out of healthy eating habits. If the person eats too many sweets and other refined carbs, their diet consists of processed and canned foods, and their general calorie intake is high—they will likely gain weight with parasites or without them. In this occasion, infection is merely a trigger.

Hormone levels

A type of tapeworm called Taenia taeniaeformis is associated with lower leptin levels. Leptin is a hormone that controls feelings of hunger and saturation. Lower leptin levels mean that there will be no sense of fullness after a meal. While the main hosts for T.taeniaeformis are cats, certain human parasites, such as Entamoeba histolytica and Strongyloides, also affect leptin secretion.

Insulin resistance

Insulin resistance is an occurrence when cells become resistant to insulin and do not consume glucose from the blood to get energy. As a result, the organism receives less energy, the patient experiences tiredness over their normal levels, and blood sugar levels are elevated. Insulin resistance is a cause of type 2 diabetes. The body then stores excess blood sugar as fat.

Studies emphasize a high prevalence of hyperglycemia (high blood glucose) in patients with parasitic infections, especially hydatidosis and cysticercosis (caused by tapeworms). While the available data on the subject is limited and further research is needed, it should not be neglected.


The presence of foreign organisms in the body and the toxins they release cause chronic inflammation. Long-term inflammation makes adipose (fat) tissue produce proinflammatory mediators and promote cellular proliferation which leads to hypertrophy and insulin resistance.

Alterations to gut bacteria

Our gut microbiome controls a lot of the metabolism and foods we want. Parasites cause irritated bowel syndrome, change bowel movements, and overall antagonize our healthy gut bacteria. This explains changes in appetites, unusual cravings, digestive disorders—and, in the long run, weight gain caused by intestinal worms.


If you suspect you have been infected with parasites, contact your healthcare provider right away. They have several methods to diagnose the issue.

Stool tests

A sample of the patient’s feces can be examined under a microscope to discover the worms’ presence.

Medical imaging

MRI or CT scans can detect cysts in the tissues and help diagnose cysticercosis.

Blood tests

In the event of parasitic infections, the body forms an immune response and produces antigens specific to worms. They can be detected with a blood test.


If parasites cannot be found in stool samples, a colonoscopy may be necessary to examine the patient’s intestines.

Intestinal Worms Prevention and Treatment

Hygiene practices

Proper hygiene reduces the risk of contracting and ingesting the parasite. It includes:

  • wash your hands regularly, especially before and after cooking, before and after using the toilet, and after touching soil;
  • drink bottled or boiled water, especially in areas without modern sewage systems and toilets;
  • thoroughly wash fresh fruits and vegetables before eating them;
  • conduct regular anti-worm prophylactics for your pets;
  • do not eat undercooked meat or fish; unwashed fruits and vegetables;
  • do not walk barefoot and do not let children play in the areas where animal feces may be present.

Medications for worm infections

Some medications work on a wide variety of intestinal parasites, and some are FDA-approved for very specific cases. Depending on your diagnosis, your doctor may prescribe:


Intestinal parasitic infections are very common in humans. In some cases, worms cause weight gain by causing inflammation, affecting metabolism, and altering the mental health and eating habits of the affected patient.


Can worms in the stomach cause weight gain?

Worms rarely live in the stomach due to the acidic environment. Nevertheless, parasitic invasion can trigger sudden weight changes.

Do pinworms make you gain weight?

It does not occur as a general rule, but it is possible.

Can worms affect your weight?

Yes, sudden and otherwise unexplained weight changes may be a symptom of a parasitic infection.

Can parasites cause overweight?

That is individual but possible.