Diseases & Conditions A - Z
powered by Talix

What causes unintentional weight gain? 19 possible conditions

Unintentional weight gain occurs when you put on weight without increasing your consumption of food or liquid and without decreasing your activity. It’s often due to fluid retention, abnormal growths, constipation, or pregnancy. Unintentional weight gain can be periodic, continuous, or rapid.

Periodic unintentional weight gain includes regular fluctuations in weight. One example of unintentional weight gain is experienced during a woman’s menstrual cycle. Periodic, but longer-term unintentional weight gain is often the result of pregnancy, which lasts 9 months.

Rapid unintentional weight gain may be due to medication side effects. Many cases of unintentional weight gain are harmless. But some symptoms experienced along with rapid weight gain may signal a medical emergency.

What causes unintentional weight gain?


The most common cause of unintentional weight gain is pregnancy. But many women do intentionally eat more to support the growth of the baby. During pregnancy, most women put on weight as the baby grows. This extra weight consists of the baby, placenta, amniotic fluid, increased blood supply, and an enlarging uterus.

Hormonal changes

Between the ages of 45 and 55, women enter a 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 too low 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.

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

Other medical conditions affecting hormone levels can cause weight gain in both sexes. These include:

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


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

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

Fluid retention

Unexplained rapid weight gain may be the result of fluid retention. Fluid retention, also known as edema, can cause your limbs, hands, feet, face, or abdomen to look swollen. People with heart failure, kidney disease, or those taking certain medications may experience this type of weight gain.

You should always report rapid weight gain and fluid retention to your doctor, even if no other symptoms are present.


Unintentional weight gain can be due to certain medications, including:

  • corticosteroids
  • antidepressants
  • antipsychotic medications
  • birth control pills

What are the symptoms of unintentional weight gain?

Depending on the cause, symptoms of unintentional weight gain can differ from person to person. Symptoms associated with this type of weight gain include abdominal discomfort or pain and bloating.

You can also experience visible swelling in the abdomen and other areas of the body, or the extremities (arms, legs, feet, or hands).

You should see a doctor immediately if you experience the following symptoms:

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

When these symptoms accompany unintentional weight gain, they can sometimes signal a serious condition.

How is unintentional weight gain diagnosed?

Your doctor will ask several questions about your symptoms, lifestyle, and medical history. Your doctor also may take a blood sample to check hormone levels, kidney function, and other health markers that can show medical problems.

An imaging test like an ultrasound, X-ray, MRI, or CT scan may be necessary.

What are the treatment options for unintentional weight gain?

There are several ways to treat unintentional weight gain. The best method of treatment depends on the cause of your unintentional weight gain.

If a hormonal imbalance is the cause, your doctor may prescribe medication to balance your hormone levels. The medication will depend on what hormones are affected. These medications are often used long-term.

If medication is the cause of the problem, your doctor will recommend alternative treatments.

Content licensed from:

Written by: April Kahn
Medically reviewed on: Feb 02, 2017: Peggy Pletcher, MS, RD, LD, CDE

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
Symptom Search
Enter your symptoms in our Symptom Checker to find out possible causes of your symptoms. Go.
Drug Interaction Checker
Enter any list of prescription drugs and see how they interact with each other and with other substances. Go.
Pill Identifier
Enter its color and shape information, and this tool helps you identify it. Go.
Drugs A-Z
Find information on drug interactions, side effects, and more. Go.