Unintentional Weight Loss: Causes & When to Worry

By Chris Bodle, MD
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March 26, 2020

Your weight is determined by so much more than what you eat—-your activity level, health, age, nutrient absorption, and economic and social factors can all play a role in how much you weigh. It’s common to gain or lose weight—in fact, daily weight fluctuation is completely normal. However, if you’re noticing that you’re losing weight unintentionally without dieting, exercising, or changing your lifestyle, it’s worth taking notice. Unexplained weight loss, defined as losing 10 or more pounds (or 5% of your body weight) over 6-12 months, could be the sign of an underlying condition.

Why Am I Losing Weight?

Weight loss can be intentional—you may diet or exercise to lose weight. In other cases, weight loss can be unintentional, and you find yourself losing muscle mass, body fluid, or fat without even trying. It’s not uncommon to lose body fluid when you take certain medications, don’t drink enough, or if you have a health condition like diabetes. Body fat loss can come from exercise, dieting, or after pregnancy, when it’s normal to lose weight.

Unintentional weight loss may be a sign of an underlying medical disorder, especially if it’s persistent or significant. Extreme weight loss can be a sign that your diet lacks the right amount of nutrients and that you’re experiencing malnutrition.

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When to Worry About Weight Loss

Your body’s weight can fluctuate but when you lose more than 5% of your weight over 6-12 months, that’s typically a reason for concern.

Pay attention if you experience other symptoms, such as:

If you’re experiencing other symptoms, it’s a good idea to seek the advice of your doctor.

Causes of Weight Loss

Unexplained weight loss can be caused by physical, psychological, or environmental changes that range from mild to serious. Some causes of rapid weight loss include the following:

Hormonal changes

You may experience weight loss if you have a problem with the glands that secrete hormones that can impact your appetite. Examples include:

  • Addison’s disease: Your adrenal glands don’t produce enough cortisol and aldosterone.
  • Type 1 diabetes: Your kidneys remove unused glucose in the urine and calories leave your body as unused sugar.

Thyroid disorders

Thyroid disorders involve abnormal production of thyroid hormones which can impact your diet. Examples include:

  • Hypothyroidism: An underactive thyroid may cause you to gain weight.
  • Hyperthyroidism: An overactive thyroid may cause you to burn calories quickly even if you have a good appetite.

Gastrointestinal issues

Gastrointestinal issues can disrupt the hunger hormone, ghrelin, and the satiety hormone, leptin, leading to a decreased appetite. Examples include:

Bacterial, viral, or parasitic infection

These conditions, including HIV and AIDS, can bring on sore throats and mouth sores, which can make eating uncomfortable.

Dental problems

Dental issues can make eating difficult, particularly if you’re losing teeth or experiencing mouth ulcers.


Cancer raises inflammation, in turn interrupting hormones that regulate appetite, and many cancer treatments and medications can cause nausea or a decrease in appetite. Examples of cancers that cause unexplained weight loss include the following:

  • Pancreatic cancer
  • Lung cancer
  • Stomach cancer
  • Esophageal cancer

Eating disorders

When you have an eating disorder your irregular eating habits and behavior will likely cause you to lose weight. Those suffering from anorexia, lack or loss of appetite, or bulimia, bouts of extreme eating followed by self-induced vomiting, are especially vulnerable to extreme weight loss.

Life changes

If you’re experiencing significant life change or trauma, it may change your eating habits. Examples include:

Mental conditions

Those who suffer from depression or anxiety may find that their hunger levels change as parts of the brain that control appetite may be impacted. Additionally, those suffering from dementia may be unable to communicate their hunger needs.

Risk Factors and Complications

Anyone can experience unintentional weight loss. However, it’s most common and most serious in those who are over age 65 as it may be the sign of a serious mental or psychiatric condition.

When you lose weight rapidly, you put physical demands on your body which can cause complications including:

Healthy Ways to Gain Weight

If you’ve experienced rapid, unexplained weight loss, your doctor may recommend you gain weight. Gaining weight can be challenging, depending on your condition. You may want to consider the following ways to gain weight while still maintaining your overall health:

  • Drink shakes and smoothies: Add in ingredients like fruits, nut butter, nuts, yogurt, greens seeds, or milk. Avoid filling up on coffee, diet soda, and other beverages which lack nutrients but can be high in calories.
  • Add flavor: Enhance the flavor of your food with spices to make eating more appealing.
  • Eat more often: Instead of consuming two to three large meals a day, consider increasing how often you eat with five to six smaller meals daily.
  • Consult a nutritionist or dietitian: A professional can counsel you and provide recommendations for the best way to gain weight given your circumstances.
  • Add calories to your meal: Consider adding cheese, eggs or nuts to some of your meals to up their calorie count.
  • Enjoy a bedtime snack: Add a nutritious snack before bedtime, like a peanut butter and jelly sandwich, a wrap stuffed with sliced veggies, cheese or avocado.
  • Try strength training: The benefits of strength training are two-fold—building muscles can help you gain weight, and exercise may stimulate your appetite.

When to See a Doctor

You should consider seeing your doctor to understand the underlying cause of your weight loss if:

  • You’ve lost more than 5% of your body weight or 10 pounds without trying over 6-12 months
  • You’re over 50 and have underlying health conditions
  • You’re experiencing symptoms beyond just unexplained weight loss

Your doctor will take your medical history and do a physical exam. They may do additional testing such as blood tests, imaging studies (such as MRI or CT scan), or procedures like an endoscopy or echocardiogram to assess what is causing your weight loss. If your doctor can’t pinpoint a cause, they may suggest you come back after at least a month. You may be put on a special diet to help you regain the weight you lost, or to prevent additional weight loss.

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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Chris Bodle, MD

Dr. Bodle is a board certified emergency medicine physician. He received his medical degree from Indiana University School of Medicine, and completed his residency in emergency medicine at Emory University. In addition to K Health, he currently works as an Emergency Medicine physician in an Urban, Level 1 Trauma Center in the south east.

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