Unintentional Weight Gain

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Weight gain that occurs when your weight increases without increasing your food intake has many causes. Here's a look at some of the more common underlying reasons for weight gain:


Thyroid hormone deficiency may slow metabolism, resulting in weight gain from fat gain and water retention.

Symptoms of hypothyroidism can include fatigue, lethargy, swelling of the face or around the eyes, dry, coarse skin, decreased sweating, poor memory, slow speech, and hoarse voice, weakness, intolerance to cold and headache.

Cushing's Syndrome

Cushing's syndrome is a disorder caused by an excess of the hormone cortisol. Fat accumulates in the face, abdomen and upper back, often producing a characteristic rounded "moon" face and "buffalo hump". The arms and legs usually remain slender.

Other symptoms of Cushing's syndrome include muscle wasting and weakness, thin skin, poor wound healing, easy bruising, purple "stretch marks" on the abdomen, menstrual irregularities, high blood pressure, glucose intolerance and hair loss in women.


Hormone replacement therapy and oral contraceptives containing estrogen can cause fluid retention and increased appetite. Other drugs that can cause weight gain are nonsteroidal anti-inflammatory drugs (NSAIDs), antidepressants, and diabetes medications.

Polycystic Ovarian Syndrome

Affecting approximately 5 million reproductive-aged women in the United States, polycystic ovarian syndrome (PCOS) is a condition that results in weight gain, difficulty becoming pregnant, irregular or absent menstrual periods, acne, thinning scalp hair, ovarian cysts, and excess hair growth on the face and body.

Hormonal Changes of Menopause

Declining estrogen during midlife can cause women to experience weight gain around the abdomen and hips.

Weight Gain Associated With Menstruation

Some women may experience bloating and fluid retention around the time of their menstrual period.

Fluid Retention

Conditions such as heart, liver, or kidney disease can cause fluid retention (also known as edema), which can appear as swelling in the eyes, hands, feet, face, abdomen and/or arms and legs.


People with poorly controlled diabetes may gain weight because their bodies are unable to properly convert food into energy.

Food Allergies and Sensitivities

Eating foods to which you are allergic can result in inflammation and lead to weight gain. Much of the weight gained is fluid retention caused by inflammation and the release of certain hormones.

Other Causes

Besides the conditions above, there are other reasons why someone may gain weight or feel bloated, such as:

  • Stress 
  • Digestive conditions, such as irritable bowel syndrome (IBS), gastroesophageal reflux disease (GERD), ulcers, constipation, small intestine bacterial overgrowth (SIBO)
  • Cancer - e.g. ovarian cancer
  • Pregnancy

Bottom Line

Any unexpected change in your body, including weight gain, should be checked by your healthcare provider. Note any other symptoms that you may be having and your care provider can perform tests to see if there is an underlying condition responsible for the weight gain.&

If you have difficulty breathing, shortness of breath, heart palpitations, changes in vision, swollen feet, fever, vision changes, or other symptoms, or if your weight gain is rapid, be sure to seek medical care immediately.

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Article Sources
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