18 Reasons You’re Losing Weight for Seemingly No Reason, According to Doctors

Weight loss is a common symptom of hyperthyroidism (overactive thyroid) says Anne Cappola, M.D., an endocrinologist and professor of medicine at the University of Pennsylvania. This means your thyroid—the butterfly-shaped gland in your neck that helps regulate your metabolism and growth—is pumping out too many hormones, resulting in a slew of body changes.

“If I suspected a thyroid issue, I’d probably look for increased hunger or heart palpitations,” she explains. Sleeping problems or feeling hot all the time are also common symptoms of an overactive thyroid, she says.

Treatment: Medication is often required to manage an overactive thyroid condition.

Dr. Hildreth mentions something experts refer to as the “obesity paradox.” Later in life, weight loss—not weight gain—is associated with a greater risk of death. “As we age, the stomach empties more slowly, which makes you feel fuller longer,” she says. “Also, some of the brain signals that control appetite and fullness become attenuated,” Dr. Hildreth adds. All of this can lead to older adults eating less, losing weight, and failing to get enough nutrients to support their bodies’ needs.

Treatment: Consult a registered dietitian or healthcare professional and find a meal plan that works for you. Be sure you’re eating enough protein to help your body carry out important bodily functions, like curbing hunger, stabilizing blood sugar, and building muscle mass—which people lose as they get older. “Many medications can also affect your appetite, so you need to pay attention to how much and how often you’re eating,” Dr. Hildreth adds.

Celiac disease—an autoimmune disorder in which ingesting gluten causes damage to the small intestine—can lead to a drop in weight, and tends to be accompanied by other GI symptoms like bloating and diarrhea, says Jamile Wakim-Fleming, M.D., a gastroenterologist at Cleveland Clinic.

If you have celiac disease and eat gluten, your immune system can go a little out of whack. This reaction can mess with the lining of your small intestine, hampering its ability to help you absorb nutrients properly, according to the Mayo Clinic.

Treatment: According to the Celiac Disease Foundation, the only treatment for celiac disease at the moment is to adhere to a strict gluten-free diet.

Dr. Ali notes that stress and depression can make weight fluctuate to some extent. Loss of appetite is a common side effect of clinical depression and one that can promote unexplained weight loss if you’re unaware that your mood swings are something a bit more serious. “In a lot of cases, the person doesn’t even notice they’re losing weight because they’re mired in the depression,” Dr. Cappola explains. Irritability, heavy drinking, indecision, and problems sleeping are other common symptoms of depression.

Treatment: Talk to your medical provider to find out your treatment options. Many doctors will prescribe antidepressants and talk therapy.

Problems with your pancreas, which produces enzymes that aid in digestion, can also lead to unexplained weight loss, Dr. Wakim-Fleming says. People with chronic pancreatitis—a disease in which the pancreas becomes inflamed—tend to lose weight quickly (even if they are eating normally) because the body simply doesn’t produce enough enzymes for proper digestion of food to occur, according to The National Pancreas Foundation. Look for symptoms like stomach pain, discolored (or oily) poop, diarrhea, or nausea after eating fatty foods.

Treatment: Your doctor might prescribe painkillers, a change in diet, and antibiotics if you have an infection, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

“Especially early on, new-onset diabetes can cause weight loss,” Dr. Cappola says. While this typically occurs in a type 1 diabetes diagnosis, it can occur in type 2 as well, per the Cleveland Clinic. You may also feel super thirsty and notice you’re peeing all the time. “Your body is literally peeing out glucose because you can’t absorb it, and that drives thirst,” she explains. If you have continuously high blood sugar frequently, it can cause your body to suck nourishment from your muscles, which fuels the sudden weight drop.

Treatment: Your doctor may prescribe oral drugs for prediabetes or type 2 diabetes. Or in cases of type 1 diabetes and some type 2 diabetes, insulin therapy will be required.

Dr. Hildreth says inflammatory conditions like rheumatoid arthritis (RA)—an auto-immune disease where your immune system attacks your healthy tissues by mistake—or some types of infection can knock out a sufferer’s appetite, causing a drop on the scale. These conditions can also cause inflammation in your gut, which could mess with nutrient absorption, leading to unexplained weight loss before diagnosis.

Treatment: RA can be treated and managed with medications like disease-modifying antirheumatic drugs (DMARDS) and biological response modifiers (biologicals). Some may choose to add pain management strategies to their treatment plan, too, according to the Centers for Disease Control and Prevention (CDC).

Addison’s disease is a condition of the adrenal glands where they don’t produce the right amounts of cortisol and aldosterone. Though not very common, Addison’s disease can cause endocrine-related weight loss that presents itself with thirst, salt cravings, and weakness, says Rekha Kumar, M.D., endocrinologist and associated professor of Clinical Medicine at Weill Cornell. This is because the adrenal glands aren’t functioning properly, which may throw your metabolism off.

Additionally, Addison’s disease impacts the salt and water balance in your body, blood pressure, and your ability to manage stress, says Lydia C. Alexander, M.D., chief medical officer at Enara Health and president-elect of the Obesity Medicine Association. Weight loss can happen due to loss of appetite from nausea or abdominal pain, fatigue, or dehydration, she adds.

Treatment: Medication is often prescribed to treat Addison’s disease, according to the Mayo Clinic, which may include hormone replacement therapy or corticosteroids.

As you age, Dr. Kumar says it’s very common to experience muscle loss from lack of physical activity, which can turn into weight loss. This is because muscle is heavier than fat, which can tip the scale lower.

“This is particularly a serious concern in adults over age 65. One of the biggest concerns resulting from unintentional weight loss in this group is Sarcopenia, meaning loss of muscle mass and strength,” warns Dr. Anegawa. “Sarcopenia is associated with worsening functional impairment, disability, falls, and mortality.”

Treatment: A healthy diet and regular exercise can help you build back muscle that has atrophied, according to the Cleveland Clinic.

Though weight loss isn’t necessarily a symptom of autoimmune disease Sjögren’s syndrome (a disease that impacts saliva production), the condition may cause you to not be eating as you normally would, Dr. Kumar says. Though an autoimmune disease would present itself alongside other symptoms beyond weight loss, she notes.

Treatment: Sjogren’s syndrome is often treated based on the parts of the body that are affected. Plenty of people manage dry eye and dry mouth symptoms via over-the-counter eye drops and by drinking more water. Some need prescription medications and even surgery, according to the Mayo Clinic.

Those who experience advanced heart failure tend to lose muscle mass, which can lead to weight loss, Dr. Kumar says. This is because the heart is working so hard to function properly, you’re burning more calories than you normally would, she adds.

Dr. Alexander adds, other heart conditions like heart disease, endocarditis, or pulmonary disease can also lead to weight loss. For example, those who have bacterial endocarditis may experience fatigue, fever, and poor appetite, which could cause a loss of weight and muscle mass, she says.

Treatment: Treatment for heart conditions vary based on the condition, but often prescription medications, altered diet, and even surgery or other procedures are needed, per the Mayo Clinic.

Dr. Kumar says parasites or worms can take up all your calories, so you’ll find that you’re eating as normal but are still dropping pounds unexpectedly. Symptoms include abdominal pain, weight loss, feeling tired, nausea, gas, or bloating.

Treatment: The best course of action is often medication, but the type depends on what kind of parasite you’re dealing with. It’s important to see a medical professional to determine the best course of action, per Mount Sinai.

Inflammatory bowel diseases like Crohn’s disease can also result in unexplained weight loss due to malabsorption. The auto-immune condition comes with a slew of symptoms, including abdominal pain, diarrhea, weight loss, and more, per the Cleveland Clinic.

Treatment: Unfortunately, there is no cure for Crohn’s disease but there are treatments for various symptoms. Doctors may prescribe anything from antibiotics to bowel rest to surgery.

Weight loss could be a side effect of some prescription medications, according to the Cleveland Clinic. It’s best to discuss any concerns with your doctor and monitor your diet to get to the root of the cause.

Treatment: Depending on the type of medication and after discussing your options and the best method with your doctor, you might want to find an alternative medication.

A peptic ulcer happens when acid in the digestive tract eats away at the inner surface of your stomach or small intestine, the Mayo Clinic explains. Ulcers can cause you to lose weight in a few ways, says Babak Firoozi, M.D., a gastroenterologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA. “They can cause pain and, if you’re having stomach pain, it may make you not want to eat,” he says. “Usually, if you eat less, you’ll lose weight.” Another possibility is that if the ulcer is big and inflamed enough, it could prevent some of the food you’re eating from passing through the GI tract, he says.

Treatment: The right treatment for a peptic ulcer depends on what’s causing it in the first place, says Ellen Stein, M.D., a gastroenterologist and associate professor at Rutgers Robert Wood Johnson Medical School. That could mean taking antibiotics, using a medication called a proton pump inhibitor, taking medications to reduce the amount of acid in your stomach, or taking certain medications to protect the lining of your stomach and intestines.

Lupus is a disease where the body's immune system attacks healthy cells and tissues, leading to damage in several parts of the body, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases. “Lupus is an inflammatory condition and, when it’s flaring, it can impact the gut directly,” Dr. Stein says. That can lead the small bowel to absorb less nutrition and may even impact how food goes through your GI tract, she says. “It can cause a lot of pain and discomfort,” Dr. Stein says.

Treatment: There is a range of treatment options for lupus. Those can include anti-inflammatory drugs, corticosteroids to lower inflammation, immunosuppressants, and biologic medications, Dr. Stein says.

Chronic diarrhea can be caused by a range of conditions, including Celiac disease and irritable bowel syndrome, which is why it’s important to talk to a doctor if you’re regularly dealing with. “Chronic diarrhea can lead to malabsorption of nutrients,” Dr. Stein says. As a result, your body isn’t able to process the foods you take in well and you end up losing weight.

Treatment: The proper treatment for chronic diarrhea really depends on what’s causing it in the first place. If you’re having three or more loose stools a week for at least four weeks, Dr. Stein says it’s time to talk to a healthcare provider.

This is the first thing many people worry about when it comes to unintended weight loss, Dr. Firoozi says. But there is usually something else going. Still, if you have unexplained weight loss, Dr. Firoozi says your doctor should at least suspect cancer and check you out just in case.

Several types of cancer, as well as a tumor or ulcer in your stomach or intestines, can cause inflammation or malabsorption issues that may lead to a drop in weight, Dr. Wakim-Fleming says. “If someone comes to me with unexplained weight loss, I’ll check their stomach and colon and bowels for tumors or inflammation,” she says. “I’ll als0 look for tumors in the esophagus”—the tube that connects your throat and stomach—“which can make it hard to swallow.” Dr. Ali adds that battling cancer consumes a lot of calories, so the disease itself may be making you unintentionally drop pounds.

Treatment: Cancer treatments are constantly evolving, and each type and stage of cancer responds to different treatments. Some common options are chemotherapy and/or radiation therapy. Ultimately, the right treatment depends on the type of cancer you have and how advanced it is, Dr. Firoozi says. The bottom line: Don’t ignore unexplained weight loss.