9 Medical Conditions That Can Cause Unexplained Weight Loss

Rapid, continuous weight loss can signal a serious medical condition, here’s what to look out for.


We live in a culture obsessed with weight loss. But what happens when you lose weight without trying — and your body keeps losing weight?

Sudden, continuous weight loss can signal a serious underlying medical condition. On Chasing the Cure, we’ve met Sean, who's lost more than 70 pounds in a single year no matter how many calories he consumes. We've also met Heather, who's lost a substantial amount of weight and continues to be plagued by bloating whenever she eats.

While the specialists at Chasing the Cure continue their hunt for answers to Sean and Heather’s health challenges, let’s have a look at nine medical conditions that can cause sudden, unexplained weight loss.

Hyperthyroidism. The thyroid gland helps regulate your body’s metabolism. When the gland produces too much thyroxine, the hormone responsible for metabolism, you can lose weight rapidly and experience a racing heartbeat.

Crohn’s Disease. This disease causes chronic (ongoing) inflammation in the gastrointestinal tract and interferes with nutrient absorption, causing weight loss. There are five types of Crohn’s Disease and each affects a different part of the GI tract: Ileocolitis (terminal ileum and large intestine); Ileitis (only the ileum); Gastroduodenal Crohn’s Disease (stomach and duodenum); Jejunoileitis (upper half of small intestine); Crohn’s Colitis (large intestine).

Parkinson’s Disease. When the body's brain cells that make dopamine, the chemical responsible for motor movement, stop working or die, that's called Parkinson's Disease. Common symptoms of Parkinson's are tremors, depression, smell loss, slowed stomach emptying and swallowing problems — all of which can lead to weight loss.

Addison’s Disease. Addison’s is an autoimmune disorder where the adrenal glands don’t produce enough cortisol and aldosterone (hormones responsible for tissue and organ function). Weight loss is a common symptom in those with Addison’s along with vomiting, fatigue, loss of appetite, abdominal pain and dehydration.

Cancer. According to Cancer.net, 40 percent of people with cancer say they experienced unexplained weight loss when first diagnosed. The reasons for weight loss with cancer have several potential causes, including loss of appetite, changes to the body’s immune system, nausea and vomiting, fatigue and loss of taste.

Parasitic infection. Intestinal parasites like to feed on the same things we do and can rob the body of the nutrients it needs. If you’ve experienced sudden weight loss after a trip abroad, eating rare steak, consumed water from a questionable source or have other digestive issues along with your weight loss, it could be time to see a doctor for a simple test to see if you have an intestinal parasite.

Diabetes. Sudden weight loss can be a warning sign of diabetes. When the body loses its ability to regulate its blood sugar, it looks for other ways to get the energy it needs. The body will turn to fat and muscle tissue and burn those for fuel, potentially exposing organs to long-term damage if blood sugar and insulin levels go unregulated.

Dementia. While the connection isn't exactly known, weight loss can be an early sign of dementia. It's also common in the end stages of the disease. Memory issues can affect remembering to eat on top of challenges with chewing, swallowing and digestion.

Anxiety. For those with undiagnosed anxiety issues, weight loss is a common side effect. When the body is always in a fight-or-flight state, organs operate in constant overdrive. This overdrive status can increase metabolism and cause the body to burn more calories. Anxiety can also suppress the appetite, making it difficult or undesirable to eat.

It’s worth noting that several other medical conditions can cause sudden, unexplained weight loss, and you should bring weight loss up with your doctor if you have a concern. While the initial drop of pounds might bring a smile to your face, weight loss that happens when you haven't changed anything about your day or diet could be a sign there's something more serious going on. It never hurts to ask if the weight loss you're experiencing is healthy.

Sean's Story Was First Featured in Episode Three of Chasing the Cure

E. Napoletano is an award-winning journalist and the recipient of the 2019 Illinois Women’s Press Association first-place prize for her feature on the traumatic effects of family separation policies at the border.