This Is Why You Started Gaining Weight Out of Nowhere

Updated 04/17/19

There's no discovery quite as startling as stepping on the scale and weighing way more than you thought you did (or trying on your favorite pair of pants only to realize that they fit a little tighter than they did the week before) with absolutely no idea why.

Most of the time we can pinpoint our weight gain from, say, an overly indulgent vacation in which we downed a dessert with every meal or a newfound affinity to eat out on the regular. But, then there are those times when we experience unexplained weight gain—the kind of weight gain that seems to show up overnight, out of nowhere, and seemingly for no reason.

When you can't find a culprit for why you are gaining weight, it might be one of these seven sneaky reasons.

Keep reading to see what they are and what you can do about it.

Lack of Sleep

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Not getting enough sleep has been scientifically linked to significant weight gain. The Mayo Clinic reports that in one study, women who slept less than six hours a night were more likely to gain 11 pounds than women who slept at least seven hours each night. This is likely due to the effect that insufficient sleep has on the hormones that regulate appetite—stimulating the ones that tell you you're hungry. It may also be due to the fact that when you're tired, you're less likely to exercise or move as much throughout the day.

So be sure you're clocking enough shut-eye, as your chronic late nights might be adversely affecting your waistline. 

Your Medication

unexplained weight gain

When you gain weight, the first place you look for answers is often your diet or exercise routine, but the culprit can be hiding in your medicine cabinet. Many medications, including ones that treat migraines and mood disorders, as well as birth control and steroids, can cause weight gain for a variety of reasons. If you suspect a medication you're taking might be causing weight gain, talk to your doctor to discuss your options. 


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Like with insufficient sleep, stress can cause weight gain because of hormones. When the body experiences stress, it causes a surge in the hormone cortisol, which leads to an increased appetite (to fuel your fight-or-flight response). On top of that, stress is often the reason you can't fall asleep at night, or what wakes you up and keeps you up in the middle of the night—aka a double whammy to your midsection. Exercising regularly is an easy solution—working out not only lowers stress, it also (obviously) helps with weight loss.


Your Job

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If you've had a nine-to-five desk job for a while, you might not suspect it as a reason for weight gain, but the realities of office life go beyond the sedentary nature of it and can compound quickly. Maybe a new project has you working late nights (and thus you're not getting enough sleep—see slide one, and super stressed—see previous slide), and/or you're too busy to throw together a healthy lunch, so you're eating more fattening fast food than you realize. Throw in some mindless snacking on communal food in the kitchen, and a co-worker's birthday donuts for the team, and your extra pounds might just be explained.



Sometimes the simple reason behind the scale reading a surprising number is your sodium intake. When sodium is the culprit, you haven't actually gained body fat; your body is just retaining water weight (to dilute the sodium). Salt aside, unlikely sources of sodium include many salad dressings and sauces, frozen meals, and bread. If you focus on cutting back on sodium, the "weight" should disappear shortly. 

Water Retention

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Again, like with sodium, water weight isn't fat, but it can tip the scale in an unsettling direction and make you feel heavier. Though it might sound counterintuitive, the solution to clearing that water weight is to drink more water. The reason your body seems to be holding on to the water weight is because you're not drinking enough fluids, so it thinks it has to store the water it doesn't have in reserve. 

Weight Training

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Confusingly, you might find that you've gained weight after you start working out more, which can happen for two reasons. First, weight training increases muscle mass, and muscle is more dense than fat, so as you lose fat and increase muscle, you might see a higher number on the scale. Second, weight training causes muscle inflammation (the soreness you feel afterward), which means the muscle swells from water retention to protect it. The good news is that although weight training, especially when you're just starting out, might cause slight weight gain, it will help you lose inches—which means even if the number on the scale reads slightly higher, your clothes will fit better.


Want to learn more about weight gain and how to deal with it? Check out what do do when you've realized you've gained five pounds.

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