Sometimes when you have to loosen a notch in your belt, you have a good idea of what led to the sudden weight gain. But there are times when unexpected weight gain may have you scratching your head because you haven’t done anything differently. When it’s not obvious why you’ve added some extra digits to your reading on the scale, here’s what might be going on.

Watch Your Sodium

While salt is a natural flavor enhancer, eating too much sodium can cause your body to retain water, and that extra water, as you guessed it, adds some extra weight. The recommended amount of sodium per day is 2,300 mg, which may seem like more than enough, but the average American tends to eat more than 3,400 milligrams of sodium each day, according to the CDC.

Americans get about 70% of their daily sodium from processed and restaurant foods, Restaurant food — especially fast food — tends to be loaded with sodium. The same is true of pre-packaged snacks or convenience items. All that salt may help make the item more shelf-stable and tasty, but if you eat enough salty foods several days in a row, you may suddenly gain weight from fluid retention.

Keep in mind, there are a few pantry staples that can be “sodium bombs” as well, such as bread, cold cuts, canned soups and cured meats such as pepperoni or jerky.

Beyond the weight gain, excess sodium can increase your blood pressure and your risk for heart disease and stroke. Be mindful of your sodium intake, especially since it can sneak its way into things you wouldn’t immediately think of, such as some breakfast cereals.

New Medication

Believe it or not, there are many medications that have weight gain as a possible side effect. The biggest culprits are the eight medication classes listed below:

• Antidiabetics
• Antidepressants or mood stabilizers
• Antipsychotics
• Anticonvulsants
• Antihistamines
• Beta blockers
• Steroids
• Oral contraceptives

Of these, medications to help treat depression (including SSRIs) and beta-blockers to treat heart disease are the two most common culprits.

If you’re undergoing testosterone therapy or have added testosterone-boosting supplements to your diet, these can also affect your weight since they act on your hormones.

If you recently started a new medication or supplement and notice a bump in weight gain, talk to your health care provider. There may be an alternative medication they can switch you to that doesn’t have the same effect on your weight. The Obesity Action Coalition has a great resource on their website listing out the most commonly prescribed medications in the classes listed above, as well as possible alternatives you could talk to your doctor about.

Keeping an Eye on Your Endocrine

Endocrine disorders are almost notorious for affecting weight, whether it be unexplained weight gain or weight loss. One of the most common endocrine disorders that cause weight gain is hypothyroidism, or an underactive thyroid. In fact, nearly 5 out of 100 Americans ages 12 years and older have hypothyroidism.

While hypothyroidism is more common in women, it still affects men, and can cause sudden, significant, and unexplained weight gain.

That being said, weight gain isn’t the only symptom of an endocrine disorder, and you will most likely have other symptoms, such as fatigue, weakness, a lower tolerance to cold environments, dry skin or dry, thinning hair, headaches, problems with concentration or focus, depression and unexplained joint or muscle pain.

Thankfully, hypothyroidism is typically incredibly easy to treat and control. After testing to confirm an underactive thyroid, your physician will most likely prescribe medication to replace the hormones your thyroid is having a hard time making. 

Carbs, Carbs, Carbs

Carbohydrates are found in a variety of foods — both healthy and not so healthy — such as breads, milk, potatoes, cookies, spaghetti, soft drinks and corn. While carbohydrates are a part of a healthy, balanced diet because they provide energy for our bodies, it can be easy to go overboard with them. It’s recommended that 45 to 65 percent of your total daily calories come from carbs, which roughly translates to about 225 to 325 grams of carbs a day based on a 2,000-calorie diet.

When we eat carbs, our bodies store them as glycogen in our muscles and liver, and each gram of glycogen contains about three grams of water. So a carbo-loaded meal can cause an increase in water stored in your tissues. Moreover, if you consume more carbs than your body needs to burn for energy, that extra energy will get stored for later, which isn’t necessarily a bad thing. But if you keep consuming more carbs than your body needs, that extra storage of carbs will be converted into fat.

You Recently Lost Weight

Yep, that’s right. If you recently worked hard to lose some pounds, unfortunately, your body weight and body fat are tightly regulated, and your system will try to maintain balance, even if you’re keeping up with your weight-loss routines.

However, don’t let this discourage you. If you’re maintaining eating healthy and exercising regularly, the amount of weight you gain back will be less than what you initially lost.

The Takeaway

There are many reasons why you may unexpectedly gain weight, but thankfully most can be easily counteracted. But if you try to course correct and are still gaining weight or are having a hard time shedding weight, it’s worth bringing up with your health care professional who can look into other reasons.