Slideshow: Weight Gain Shockers - Surprising Reasons You're Gaining Weight

What's With the Weight Gain?

If you start taking in more calories than usual or cut back on exercise, you wouldn't be surprised if the numbers on the scale crept higher. But what if you're doing everything the same as you always do and your weight still goes up? It's time to delve a little deeper into what might else be going on.

Lack of Sleep

There are two issues at work with sleep and weight gain. The first is intuitive: If you're up late, the odds are greater that you're doing some late-night snacking, which will increase your calorie intake. The other reason involves what's going on biochemically when you're sleep deprived. Hormones that affect appetite take over, making you hungrier the next morning. These hormones also make you feel not as full after eating.

Stress

When life's demands get too intense, our bodies go into survival mode: Cortisol, the "stress hormone," is secreted, which causes an increase in appetite. And then of course, we may reach for high-calorie comfort foods in times of stress as well. This combination is a perfect breeding ground for weight gain.

Antidepressants

An unfortunate side effect from some antidepressants is weight gain, which may occur in up to 25% of people taking them long-term. Talk to your doctor about switching to another drug if you think your antidepressant is causing weight gain. But realize that some people experience weight gain after beginning drug treatment simply because they're feeling better, which leads to a better appetite.

Other Drugs That May Cause Weight Gain

Several other prescription drugs have been associated with weight gain. The list includes antipsychotic drugs (used to treat mood disorders like schizophrenia and bipolar disorders), along with medications to treat migraines, seizures, high blood pressure, and diabetes. Work with your doctor to find a medication that treats your symptoms without disrupting side effects.

“The Pill” Does NOT Cause Weight Gain

Contrary to popular belief, combination birth control pills (estrogen and progestin) do not cause weight gain. In fact, some women on the pill lose weight, primarily from nausea. If you're still concerned about possible weight gain, talk to your health care provider.

Hypothyroidism

If your thyroid (the butterfly-shaped gland in the front of your neck) is not making enough thyroid hormone, you're probably feeling tired, weak, cold, and gaining weight. Without enough thyroid hormone, the metabolism slows, making weight gain more likely. Even a thyroid functioning at the lower end of the normal range might cause weight gain. Treating hypothyroidism with medication may reverse some of the weight gain.

Menopause

Don't blame menopause and the loss of estrogen for your midlife weight gain. These all may occur around the same time, during your 40s or 50s, but changing hormone levels probably aren't the cause. Aging slows the metabolism, so you burn fewer calories, and any changes in lifestyle (e.g. exercising less) play a role. But where you gain weight may be related to menopause, with fat accumulating around your waist, not around your hips and thighs.

Cushing's Syndrome

Weight gain is a common symptom of Cushing syndrome, a condition in which you're exposed to too much of the hormone cortisol, which in turn causes the weight gain and other abnormalities. Cushing's syndrome can occur if you take a corticosteroid for a condition such as asthma, arthritis, or lupus. It can also occur when your adrenal glands produce too much of the hormone. Weight gain may be most prominent around the face, neck or upper back, or waist.

Polycystic Ovary Syndrome (PCOS)

PCOS is a common hormonal problem in women of childbearing age. Most women with PCOS grow many small cysts on their ovaries. The condition leads to hormone imbalances that affect a woman's menstrual cycle and can lead to excessive body hair and acne. Women with this condition are resistant to insulin, which may cause weight gain. The weight tends to collect around the abdomen, putting women at greater risk for heart disease.

Smoking Cessation

On average, people who quit smoking gain about 4 to 10 pounds. Why? First, nicotine curbs your appetite, so once you quit, you may feel increased hunger pangs, which leads to overeating. Nicotine also increases your metabolism, and some people don't decrease their calorie intake to compensate for the slowdown. Lastly, nicotine is notorious for dulling the taste buds, so you may find food tastes better once you kick the habit, which can lead to overindulgence.

Rule 1: If You Do Gain Weight …

Don't stop taking any medications without first consulting your doctor. Recognize the importance of the drug you're taking. It may be critical to your health.

Rule 2: If You Do Gain Weight …

Don't compare yourself to other people taking the same drug. Not all people have the same side effects on the same drug. Even if one drug caused someone else to lose weight, the same might not be true for you. Consult your doctor.

Rule 3: If You Do Gain Weight …

Don't freak out if the weight gain is just from water retention, which is not permanent weight or fat. Once you've finished taking the drug or gotten the medical condition under control, the puffiness from fluid retention may subside. Stick to a lower sodium diet in the meantime.

Rule 4: If You Do Gain Weight …

Check with your doctor about another drug you can take. In most cases, your doctor can switch you to another medication that might not have the same side effects.

Rule 5: If You Do Gain Weight …

Learn if the weight gain is from a decrease in metabolism -- from either a medical condition or medication. And if so, take the time to participate in metabolism-raising activities. Get moving!

More Reading on Weight Gain

• Diet and Nutrition
• Obesity
• Obesity in Children
• Weight Loss and Control
• Best and Worst Beverages for Weight Loss
• 9 Best Diet Tips Ever