There are medical causes for seemingly unexplained weight gain. Here, we describe eight reasons, along with some typical symptoms and treatments.

[Editor’s note: This article was originally hosted on, our sister site.
It’s now featured here as part of our new
general-health section.]

weight-gain-scaleIf you or a loved one has unexplained weight gain or is having trouble losing weight, check out these potential medical causes. (See your health-care provider for a diagnosis and treatment options.)

  1. Hypothyroidism (underactive thyroid)
  2. Polycystic ovarian syndrome
  3. Cushing’s syndrome
  4. Lack of sleep
  5. Stress and anxiety
  6. Depression
  7. Medications
  8. Family history of obesity

Select Signs and Symptoms


  • Weight gain
  • Facial, hand, ankle, feet, leg or overall swelling


  • Weakness, fatigue, paleness
  • Joint pain or stiffness; muscle cramps, pain and atrophy; uncoordinated movement
  • Cold intolerance
  • Constipation
  • Brittle fingernails, dry skin and hair, hair loss
  • Decreased taste and smell
  • Slow speech, decreased cognitive capability
  • Depression, mood changes
  • Menstrual irregularities, infertility
  • Erectile dysfunction

1. Hypothyroidism

weight-gain-hypothyroidismLocated in the front of the neck just below the larynx, the thyroid gland secretes hormones that control metabolism. If the gland doesn’t produce enough of these hormones, you have hypothyroidism and could gain weight as a result.

Hashimoto’s thyroiditis, a disease that causes the immune system to attack the thyroid gland, is the most common reason for the condition.

Doctors diagnose hypothyroidism with one or more blood tests. Treatment includes medication and periodic hormone-level monitoring. Untreated hypothyroidism can lead to heart disease, increased risk of infection and miscarriage, and even a potentially deadly coma.


Select Signs and Symptoms


  • Obesity centered around your midsection (apple shape)


  • Irregular, scanty or absent menstrual periods
  • Infertility
  • Increased hair growth or distribution of body hair in a male pattern
  • Thinning scalp hair
  • Decreased breast size
  • Aggravation of acne
  • High blood pressure
  • Elevated insulin levels, insulin resistance or diabetes
2. Polycystic Ovarian Syndrome

weight-gain-polycysticPCOS, also called polycystic ovarian disease (PCOD), sclerocystic ovarian disease, Stein-Leventhal syndrome or syndrome O, is a leading reason for female infertility. Doctors don’t know what causes it, though Dr. Virji notes that it may result from elevated insulin levels. For whatever reason, a woman’s eggs fail to mature and be released. They accumulate as cysts in the ovaries.

PCOS usually develops shortly after puberty, but it’s “often underdiagnosed in the primary-care setting,” says Dr. Virji. “I have picked up a number of these patients in my weight-management clinic that were left undiagnosed.” Your health-care provider will need to rule out other causes of your symptoms before deciding on PCOS, says Dr. Brantley. “The diagnosis is clinical and should be a diagnosis of exclusion.”

Cushing’s Syndrome

Select Signs and Symptoms


  • Weight gain
  • Upper-body or central obesity with thin arms and legs
  • Rounded, red face
  • Increased fat between the shoulders or around the neck
  • In children: obesity and slowed growth rates


  • Fragile, thin skin that bruises easily and heals poorly
  • Purplish pink stretch marks on abdomen, thighs, buttocks, arms and breasts
  • Acne or superficial skin infections
  • Skin blushing/flushing, red skin spots
  • Weakened bones leading to easy backaches and rib and spinal-column fractures
  • Bone pain or tenderness, weak muscles
  • High blood pressure or sugar
  • Headaches
  • Thirst, increased urination
  • Fatigue
  • Irritability, anxiety or depression
  • In women: Excess hair on face, neck, chest, abdomen and thighs; irregular or stopped menstrual periods
  • In men: Decreased fertility, diminished or absent desire for sex

Treatment includes weight loss (which is harder because of the condition so be patient with yourself) and medications. If you don’t treat it, possible complications include sterility, complications associated with obesity and complications associated with abnormal periods, including cancer.

Also, PCOS may increase your risk for developing metabolic syndrome, notes Dr. Virji, with symptoms including abdominal obesity, high blood pressure and high blood sugar.

3. Cushing’s Syndromeweight-gain-measure

The body normally uses a hormone called cortisol for all sorts of good stuff, including helping break down insulin; regulating the metabolism of proteins, carbohydrates and fats; and helping the body respond to stress. If you get too much cortisol for too long, though, it can wreak havoc.

Longterm corticosteroid use and certain tumors can cause Cushing’s syndrome, also called hypercortisolism. Treatment depends on the cause and may include medications, surgery, radiation, chemotherapy or simply a slow decrease of your corticosteroids.

Untreated, Cushing’s syndrome can lead to diabetes, serious infections, kidney stones and even death.

4. Lack of Sleep
Lack of Sleep

Select Signs and Symptoms


  • Weight gain
  • Increased hunger


  • Daytime drowsiness
  • Routinely falling asleep within five minutes of going to bed (signifies severe sleep deprivation)
  • Falling asleep during sedentary activities, such as reading, listening to a lecture, watching television or sitting in the car

weight-gain-lackofsleepAccording to the National Sleep Foundation, 63 percent of American adults don’t get the recommended eight hours of sleep a night. And the less you get, the worse your weight-gain odds are.

Sleep deprivation appears to result in decreased leptin, a hormone thought to regulate appetite and metabolism, and increased ghrelin, a hormone that likely stimulates appetite. Thus, the following studies, both from November 2004, make sense:

  • Columbia University researchers found that people who get four or fewer hours of sleep a night are 73 percent more likely to be obese than those who get seven to nine hours. The researchers studied records of over 6,000 people ages 32 to 59. Get a whopping six hours a night? Count yourself 23 percent more likely to be substantially overweight.
  • In a study from the Annals of Internal Medicine, 12 young men who slept only four hours a night for two nights had a 24-percent increase in hunger, compared to when they were allowed two 10-hour nights. Cravings for high-calorie, high-carb foods especially increased.
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Getting enough sleep sounds like a simple solution. For some people, though, it’s not. “I find that obstructive sleep apnea is quite common and often missed as a diagnosis when not looked for,” says Dr. Virji. If you think you get enough sleep but don’t feel like it, you could have sleep apnea (interrupted breathing), insomnia, restless leg syndrome (urge to move your legs) or a number of other sleep disorders. See your health-care provider to determine if anything is wrong and what you can do about it.

“Additional effects of sleep deprivation,” says Dr. Brantley, “could include worsening of diabetic control, hypertension and significant changes in one’s ability to think and process information.” Sleep apnea can cause even worse results, says Dr. Northup. “There is increased strain on the heart and lungs and patients with sleep apnea have higher rates of sudden death.”

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Stress and Anxiety

Select Signs and Symptoms


  • Weight gain (or loss)
  • Excess abdominal fat
  • Eating too much (or not enough)


  • Trouble sleeping
  • Headaches
  • Constipation
  • Diarrhea
  • Lack of energy and concentration
  • Depression, anxiety, irritability
  • Stomach cramping or bloating
  • Skin problems, such as hives
  • Heart problems
  • High blood pressure
  • Neck and/or back pain
  • Reduced sexual desire
  • In Women: Difficulty getting pregnant
  • Other symptoms related to specific anxiety disorders
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5. Stress and Anxiety

weight-gain-stress“Virtually every organ system in your body can be adversely affected by chronic stress,” says Dr. Brantley, “including your heart, brain, thyroid and immune system, among others.”

But does it affect your weight?

“Stress and anxiety can lead to elevated cortisol levels,” Dr. Brantley notes. That’s the same hormone associated with Cushing’s syndrome. However, he adds, “the cortisol levels in established Cushing’s are thought to be much higher than what would be expected in a patient with stress, anxiety, etc.” For the chronically stressed, “research into the effects of long-term elevations in cortisol and its effects on obesity—and more specifically abdominal obesity—are in progress.”

One thing is certain, though: If stress and anxiety make you want to eat more, weight gain is a likely outcome, no matter what your levels of cortisol are.

“If you feel that you are having significant difficulty with stress or anxiety, see your primary-care provider to discuss the issues,” suggests Dr. Brantley. Medications and psychotherapy are available to treat anxiety disorders.

The National Women’s Health Information Center also offers the following stress reducing tips (not to replace any needed medications or psychotherapy):

  • Unwind with yoga, meditation, massage therapy, music or a book.
  • Make time for yourself—at least 15 minutes a day for a bubble bath, walk, or calling a friend.
  • Sleep.
  • Exercise.
  • Talk to friends.
  • Keep a journal.
  • Help others.
  • Get a hobby.
  • Set limits (don’t be afraid to say no).
  • Plan your time.

Select Signs and Symptoms


  • Weight gain (or loss)
  • Increased (or decreased) appetite


  • Persistent sad, anxious or “empty” mood Feelings of hopelessness, pessimism, guilt, worthlessness or helplessness
  • Loss of interest or pleasure in activities you once enjoyed, including sex
  • Decreased energy
  • Difficulty concentrating, remembering or making decisions
  • Insomnia, early-morning awakening or oversleeping
  • Thoughts of death or suicide; suicide attempts
  • Restlessness, irritability
  • Persistent physical symptoms that do not respond to treatment, such as headaches, digestive disorders and chronic pain
  • If you have bipolar disorder, you may also have cycles of mania, with symptoms that can include: abnormal or excessive elation, unusual irritability, decreased need for sleep, grandiose notions, increased talking, racing thoughts, increased sexual desire, markedly increased energy, poor judgment, inappropriate social behavior
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6. Depression

weight-gain-depressionRemember what we said about stress, cortisol and weight? The same applies here. And left alone, long-term depression can wreak havoc in your body, says Dr. Brantley. “There are good medications, as well as counseling options, that can be quite helpful and possibly life saving,” Dr. Virji says, adding, “There are some medical diseases which could be causing your depression which should not be ruled out.”

The vast majority of people benefit from treatment—and might lose weight, to boot. Talk to your health-care provider about your options. In times of crisis, an emergency-room doctor can provide temporary help.

7. Certain Medications


weight-gain-meds“Medication-induced weight gain is very common,” says Dr. Virji. “This is unfortunate since there are many medication alternatives … that can be substituted to aid in a weight-loss effort.” Medicines that can lead to increased weight, he says, include steroids and certain diabetic, blood-pressure, antidepressant and migraine medications.

“In addition,” says Dr. Bray, “anticonvulsants and antipsychotic drugs can also produce weight gain.”

To learn potential side effects of your medications, talk to your health-care provider or visit, a site run by the same folks who provide the respected Physician’s Desk Reference. Of course, don’t stop any medications unless your doctor tells you it’s OK.

The Survival Doctor's Guides to Wounds and Burns8. Family History of Obesity

If your parents are overweight, you’re more likely to carry extra pounds, too. But are genes the villain, or is it your environment? Actually, it could be either. For many, nurture is the sole culprit. For some, nature takes its toll.

But don’t jump too quickly on the inheritance bandwagon. Obesity prevalence has more than doubled in the last 40 years, but “genes do not change that fast,” says Dr. Virji. “It takes about 10,000 years to see genetic changes affecting physical [characteristics].”

Even if you are predisposed to being overweight, “The degree to which this component actually affects patients in real life is fervently argued among bariatric experts across the country and even the world,” says Dr. Virji. “I strongly believe that the majority of the problem exists in poor lifestyle choices, which happens to be very modifiable.”

Obesity has many causes, he asserts, “and there are many things that can be done to help people lose weight.”

The Experts

D. Allen Brantley, M.D., endocrinologist (hormone doctor) with the Mecklenburg Medical Group in Charlotte, North Carolina.

George Bray, M.D., former and first executive director of the Pennington Biomedical Research Center in Louisiana, where he remains as a faculty member and researcher, focusing on obesity and diabetes.

C. Joseph Northup, M.D., bariatric surgeon and assistant professor of surgery at the University of Virginia.

Ayaz Virji, M.D., author of The Skinny Book: The 6-Step Methodology for Weight Management (Verona, 2004, $7.50) and medical director of Morton Plant Mease Primary Care Weight Management in Florida.