Sudden Weight Gain: What's the Cause?

Packing on a few extra pounds isn't unusual when you haven't been physically active or if you've strayed from a healthy diet. But, when this occurs suddenly or can't be explained by your eating and exercise habits, it's worth taking a closer look.

Listen to your body

"The first thing you need to do is to rule out a medical illness as the cause," says Carson Liu, M.D., F.A.C.S., a surgeon and weight loss expert in Los Angeles.

A sudden or unexplained weight increase may have several causes:

• Medications. "Some medicines, such as certain beta-blockers, may affect your desire to exercise, leading to weight gain," says Dr. Liu. Medications such as corticosteroids, which are used to treat arthritis, asthma, and many other conditions, also may make some people put on weight. Even insulin and other diabetes medications, antidepressants, or mood stabilizers may contribute to weight gain. If you think that a prescription medicine may be affecting your weight, don't stop taking it on your own; talk with your doctor. 

• Edema. When fluid builds up in the body, swelling—also called edema—may occur. This may lead to rapid weight gain that occurs in just a few days or weeks. Edema may be caused by serious conditions such as heart failure or kidney disease. Common medications such as non-steroidal anti-inflammatory drugs also can cause fluid retention.

• Hypothyroidism. This condition occurs when the thyroid gland doesn't make enough thyroid hormone. Over months or even years, you may gain weight because thyroid hormone helps regulate your metabolism, or how quickly you burn calories. Many systems of the body may be involved, so hypothyroidism also may cause other symptoms, including fatigue, dry skin, constipation, and muscle cramps. 

• Quitting smoking. Some people gain weight soon after they stop using tobacco. Because snacking may help ease the urge to smoke, it can be easy to take in too many calories. So, stick with low-cal foods such as carrots or celery sticks if you need to nibble. Exercising regularly also may help you offset the extra food you're eating to fight cravings.

Take control

If you're gaining weight and you've ruled out a medical condition and medication, take a look at your lifestyle. Do you have healthy eating habits? Are you getting enough exercise?

If you answered "no" to either of these questions, don't panic. Make a point of being more active, after you've cleared your exercise plan with your doctor. Walks after dinner may help you unwind and burn calories.

Also, try adding more fruits and vegetables to your eating plan and replacing full-fat foods with low-fat or nonfat versions.

"You don't need to put yourself on a strict diet," says Dr. Liu. "You just need to embrace a healthier lifestyle."