You step on the scale one morning and you’re totally on track. The next morning, you’re up five pounds. WTF. Is overnight weight gain a thing?

It’s a frustrating and bewildering experience that happens to the best of us. And we’re here to tell you that you didn’t actually gain five pounds of fat in a single day. After all, gaining a single pound of fat requires consuming about 3,500 calories more than you can burn off. So to gain five pounds in a day, you’d have to eat nearly 20,000 calories in just 24 hours.

But gaining five pounds of water weight in a day? That’s easy, says Georgie Fear, RD, CSSD, author of Lean Habits for Lifelong Weight Loss. "It’s important to know that your weight will fluctuate on a daily basis, but it doesn’t mean that your weight-loss strategy is failing."

So if you step on the scale and find that you’ve magically gained a few pounds, consider these factors that can screw with the scale number.

You Hit The Gym Hard
gym exercise equipment

“After a heavy workout, especially if you perform big, compound movements that recruit a lot of large muscles, you can easily weigh a few extra pounds for several days,” Fear says.

Those microscopic tears that occur in your muscle cells after every workout heal through a process of natural inflammation. That involves some pooling of fluids around the muscle cells, which can make you puff up, she says. This does not mean you should skip those calorie-torching strength moves. Just let your muscles recover and forget about the scale.

You Consumed A Lot Of Salt
potato chips

Regardless of whether the chips are baked or fried, “excess sodium intake leads to immediate water weight gain," says Julie Ellner, MD, a San Diego-based weight-loss specialist. That can lead to swollen ankles and a belly bulge from swelling in your intestines, she says.

Apart from the water retention, munching on salty snacks can cause constipation, too.

You’ve Started A High-Protein, Low-Carb Diet
close up of sectioned plate with eggs, pork, salmon and steak

Fiber is critical to keeping your digestive system working its best. So when you miss out on fiber from whole grains, fruit, and starchy vegetables, you're bound to get backed up, says Dr. Ellner.

“If you don't go for several days, that internal traffic jam can translate to a couple pounds of retained matter,” adds Fear.

While Dr. Ellner recommends that anyone on a high-protein, low-carb diet take a fiber supplement to keep things moving, an even better option is to only reduce refined carbohydrates, like pasta, and keep whole grains, veggies, and fruit as part of your diet.