Have you ever woken up to find you gained weight overnight? Maybe your clothing, shoes, or rings are suddenly too tight. Such "sudden fat" usually isn't the result of eating too much dessert or other high-calorie foods. Rather, it's often caused by edema, which is the formal name for water retention. It's a normal reaction for an injury or inflammatory response from allergic reaction, but it can also indicate disease.

What Is Edema?

Edema occurs when fluid leaks from the body's blood vessels into the nearby tissues, leading them to swell, explains James Hubbard, MD, MPH, a family doctor who runs the website TheSurvivalDoctor.com and is the author of Living Ready Pocket Manual-First Aid: Fundamentals for Survival. He points out that edema can affect different parts of your body, including the ankles, legs, hands, feet, brain, and lungs.

The Causes of Edema

There are a number of possible circumstances and conditions that can be related to edema, says Hubbard. Some of the more common causes include:

  • Standing or sitting for an extended period of time without moving
  • Being sensitive to sodium content in foods
  • Hormonal changes, such as those that occur right before menstruation and during menopause, as well as those caused by birth control bills
  • Pregnancy, which increases blood volume and causes pressure on the womb
  • Inflammation from allergic reactions
  • Fluids leaking into the tissues caused by varicose veins
  • Kidney damage or disease, which can cause a reduction in an important protein in your urine, and/or can lead the body to retain excess fluid and sodium
  • Liver disease, which can result in an excess of fluid in the legs and abdomen
  • Improper draining of excess fluid due to damage or changes to the lymphatic system
  • Thyroid disease, which impacts the body's ability to regulate its systems
  • A weakened heart caused by congestive heart failure, which makes this organ less effective in pumping blood and leads to excess fluid build up

Treatments for Edema

There are a number of ways to treat edema, depending on the specific cause. Some typical methods of treatment include:

  • Elevating your legs
  • Wearing compression stockings
  • Engaging in physical activity
  • Reading food labels and paying attention to the sodium content
  • Eating more fruits and vegetables to avoid vitamin deficiencies
  • Changing or abstaining from troublesome medications under the guidance of your doctor
  • Taking a diuretic
  • Treating any underlying medical problems

When to Worry About Edema

While many instances of edema will respond to these simple treatment methods, more serious forms of edema may require further medical intervention. It's always best to see a doctor to determine the cause and proper treatment, especially when edema occurs with shortness of breath and/or is believed to be related to the heart, liver, or kidneys.

James Hubbard, MD, MPH, reviewed this article.

James Hubbard, MD, MPH, family doctor, email interview Jan. 27, 2014.