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What causes unintentional weight gain? 19 possible conditions

What Is Unintentional Weight Gain?

Unintentional weight gain occurs when you put on weight without increasing your consumption of food or liquid. It is often caused by:

  • fluid retention
  • abnormal growths
  • constipation
  • pregnancy

Unintentional weight gain can be periodic, continuous, or rapid.

Continuous unintentional weight gain is often the result of pregnancy. Periodic unintentional weight gain includes regular fluctuations in weight like those experienced during a woman’s menstrual cycle. However, rapid unintentional weight gain usually indicates a serious medical condition. Rapid unintentional weight gain may also be caused by medication side effects.

Although many cases of unintentional weight gain are harmless, the symptoms experienced in conjunction with rapid weight gain may signal a medical emergency.

What Causes Unintentional Weight Gain?


The most common cause of unintentional weight gain is pregnancy. During pregnancy, most women put on weight as the baby grows. This extra weight consists of:

  • the baby
  • placenta
  • amniotic fluid
  • increased blood supply
  • enlarging uterus

Hormonal Changes

Between the ages of 45 to 55, women enter a non-fertile stage called menopause. During a woman’s reproductive years, estrogen—the hormone responsible for menstruation and ovulation—begins to decline. Once menopause occurs, estrogen is so low that it isn’t sufficient to induce menstruation. A decrease in estrogen can cause women in menopause to experience weight gain around the abdominal region and the hips.

Aside from the hormonal changes of menopause, women diagnosed with polycystic ovarian syndrome (PCOS) may also experience weight gain.

Other, additional medical conditions affecting the hormones can cause weight gain in both genders. They include:

  • hypothyroidism
  • Cushing syndrome
  • increased cortisol (stress hormone) production

Hormonal changes in your middle years can cause your metabolism to slow down, causing weight gain.

Unintentional weight gain can also be cause by certain medications, including:

  • corticosteroids
  • anti-depressants
  • anti-psychotic medications
  • birth control pills


Periodic weight gain is often caused by the menstrual cycle. Women may experience water retention and bloating around the time of their period. Changing levels in estrogen and progesterone may cause some women to gain weight. Normally, this is a weight increase of just a few pounds.

This form of weight gain subsides when the menstrual period ends for the month. However, it often reappears the next month when the menstrual period starts again, and sometimes during ovulation.

Fluid Retention

Unexplained rapid weight gain may be caused by fluid retention. Fluid retention is also referred to as edema. It causes your limbs, hands, feet, face, or abdomen to look swollen. People with heart failure, kidney failure, or those taking certain medications may experience this type of weight gain. Rapid weight gain and fluid retention should always be reported to your doctor even if no other symptoms are present.

Symptoms of Unintentional Weight Gain

Depending on the cause, symptoms of unintentional weight gain can differ from person to person. Symptoms often associated with this type of weight gain include:

  • abdominal discomfort
  • abdominal pain
  • bloating
  • flatulence (gas)
  • constipation
  • visible swelling in the abdomen or other areas of the body
  • swollen extremities (arms, legs, feet, hands)

If you experience any of the following serious symptoms, seek medical care immediately:

  • fever
  • skin sensitivity
  • shortness of breath
  • difficulty breathing
  • swollen feet
  • heart palpitations
  • sweating
  • changes in vision
  • rapid weight gain

How Is Unintentional Weight Gain Diagnosed?

Your doctor will ask several questions regarding your symptoms, lifestyle, and medical history to pinpoint what might be causing your weight gain. Your doctor also may take a blood sample to test for the presence of infection. He or she will also likely check your blood for hormone levels.

An imaging test such as an ultrasound, X-ray, MRI (magnetic resonance imaging), or CT scan (computed tomography scan) may be necessary. These tests help to determine whether a fracture, abnormal growth, rupture, or inflammation is to blame.

How Is Unintentional Weight Gain Treated?

There are several ways to treat unintentional weight gain. The best method of treatment for you depends on what caused the unintentional weight gain.

If a hormonal imbalance is to blame, your doctor may prescribe medication to balance your hormone levels. The type used depends on which hormones are affected. These medications are often used long-term.

If medication is causing the problem, your doctor will possibly recommend alternative treatments.

In severe cases, when organ failure is to blame, you may need an organ transplant. Here, a surgeon removes the affected organ and replaces it with a donor organ. After having the transplant, you’ll have to take medications to keep your body from rejecting the donor organ. Swelling and unexplained weight gain are signs that your body may be rejecting the organ.

In some cases, other surgeries may be necessary. Cysts, tumors, ruptures, and fractures may all require surgery for repair or removal. The type of surgery needed depends on the nature of the condition.

Article Sources:

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See a list of possible causes in order from the most common to the least.



Bleeding or spotting, increased need to urinate, tender breasts, fatigue, nausea, and missed period are signs of pregnancy.

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The thyroid gland produces a hormone that controls how your cells use energy (metabolize). Hypothyroidism occurs when the body doesn't produce enough. Untreated, it can cause complications like obesity and heart disease.

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Gestational Diabetes

During pregnancy, some women develop high levels of blood sugar, a condition known as gestational diabetes, around the 24th week of pregnancy. In most cases, the condition develops in women who never had diabetes.

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Dysthymia is chronic depression with recurring symptoms of sadness and hopelessness lasting for several years. It is not characterized by acute depressive episodes but by an ongoing depressed feeling. Dysthymia is mos...

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There are many symptoms of the autoimmune disease HIV/AIDS, including persistent skin rashes, night sweats, and mouth sores.

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Menopause is a natural biological process in women that marks the permanent end of menstruation and fertility. Hot flashes, vaginal dryness or pain, and frequent urination are signs.

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PMS (Premenstrual Syndrome)

PMS symptoms start five to 11 days before menstruation and typically go away once menstruation begins. The cause of PMS is unknown.

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Cushing Syndrome

Cushing syndrome is when your body has abnormally high levels of a hormone called cortisol. This can occur due to overuse of corticosteroid medication, malnutrition, alcoholism, or other factors.

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Hashimoto's Disease

Hashimoto's disease is a condition that damages the thyroid's ability to function properly. It can cause a goiter, or enlarged thyroid, which can make the front of the neck look swollen.

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Postpartum Depression

Postpartum depression affects as many as 13 percent of new mothers. In the U.S., that's half a million women. Learn about symptoms, causes, risks, and more.

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Polycystic Ovarian Syndrome

Polycystic ovarian syndrome (PCOS) is a condition in which a woman's levels of the sex hormones estrogen and progesterone are out of balance. This leads to the growth of ovarian cysts.

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Bipolar Disorder

Bipolar disorder mental illness marked by extreme from mania to depression. Bipolar disorder is also called bipolar disease or manic depression.

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Acromegaly is a rare condition. It causes excess growth in the bones and soft tissues of the body. Children with the condition can grow to abnormal heights. They may also have an exaggerated bone structure that give...

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Alcoholic Liver Disease

Damage to the liver from excessive drinking can lead to ALD. Years of alcohol abuse cause the liver to become inflamed and swollen. This damage can also cause scarring known as cirrhosis. Cirrhosis is the final stage o...

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Kidney Failure

Your body becomes overloaded with toxins if your kidneys can't do their regular job. This can lead to kidney failure and even be life-threatening.

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Congestive Heart Failure (CHF)

Congestive heart failure (CHF) is a chronic condition that affects the chambers of your heart. CHF refers to fluid buildup around your heart.

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Diabetic Nephropathy

Diabetic nephropathy is a type of progressive kidney disease that occurs in people who have type 1 or type 2 diabetes. The University of Washington estimates that 20 to 40 percent of people with diabetes will ge...

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Pituitary Cancer

The pituitary gland is a very small gland of major importance to the functioning of the human body. It is located directly behind the eyes and below the front of the brain. It is about the size of a pea. Despite it...

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Ovarian Cancer

The ovaries are small, almond-shaped organs located on either side of the uterus that produce eggs. As the disease progresses, symptoms include back pain and indigestion.

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This feature is for informational purposes only and should not be used to diagnose.
Please consult a healthcare professional if you have health concerns.