8 Reasons the Scale Says You Gained Weight Overnight

Forget Monday morning blues or seeing a post from your ex on social media — what can really start your day on the wrong foot is the scale telling you that you gained weight overnight.

Sometimes you see it coming (looking at you, morning after Thanksgiving). But other times can feel like a shock because you’ve been doing everything by the book.

First things first: If you’re on a healthy eating and fitness program, don’t change a thing.

A one-day fluctuation doesn’t warrant reconfiguring your meal plan, and there’s a very real risk you’ll overcorrect and over-restrict in an attempt to get “back on track.”

Here’s what’s actually happening with that mythical scale number, and why it might have jumped so much while you slept.

Can You Gain Weight Overnight?

Yes, but the unhealthy eating pattern that produced that weight gain would have to continue for it to last.

The amount you can gain in a day is relatively small, and your body generally prefers maintaining the status quo.

So you’re less likely to see a true, lasting effect on the scale if you go back to eating well — perhaps at a slight caloric deficit — and working out the next day.

That’s why getting back on track — not necessarily compensating by undereating — is essential. “True, lasting weight gain takes days, weeks, or even months,” says Danna Hunnes, Ph.D., MPH, RD, a senior dietitian at the Ronald Reagan UCLA Medical Center.

“Even during the holidays, most people will put on at most two to three pounds.”

The problem arises when you don’t return to normal, thus the pounds stick around.

Still, Hunnes underscores that “in general terms, we cannot gain significant amounts of true weight in one day or night.”

If you see the higher number linger a week or more, then it might be time to look into other reasons why you’re gaining weight.

Why Did I Gain Weight Overnight?

The number on the scale should never upset you. If it does, Jim White RD, ACSM EX-P, and owner of Jim White Fitness and Nutrition Studios, suggests finding some other way to track your health and fitness progress, like strength goals or measurements.

But if you’re going to weigh yourself, here are the factors you should consider before altering your diet or fitness plan when you see your weight increase overnight.

1. You ate your last meal later than usual

If you pushed dinner back later than normal, you might be seeing food mass on the scale the next morning.

And if you keep a regular schedule, you’re likely accustomed to weighing yourself at a specific point in your digestion.

So you might simply be seeing your weight at a different stage in the digestive process.

2. You had more sodium or carbs than usual yesterday

“You may have had a meal loaded with sodium, which could explain why your morning weight is up,” White notes. “Sodium retains water.”

And you might not even be aware of this, especially if you’re not a label hawk.

Certain store-bought foods, like frozen meals and canned soups and veggies, can be packed with a day’s worth of sodium.

So even if you choose the low-calorie entree or veggie-heavy soup, you could see that salt reflected on the scale.

Carbs are also a notorious cause of this heart-stopping scale surge. Just look at the name: “carbohydrate,” emphasis on the “hydrate.”

One gram of this macronutrient (stored as glycogen) retains three grams of water, which is where it gets its name.

So if you follow a low-carb diet in general but reached for the bread last night, extra water may be driving that higher number this morning.

3. You upped your fiber intake

Fiber is great for you. But if you up your fiber intake too quickly, it might take some time for your body to catch up. And you might see that reflected on the scale.

“More fiber will turn into a heavier, bulkier, waterier, and more massive bowel movement. This will hold onto water, also increasing ‘weight‘,” Hunnes explains.

“However, as soon as you excrete that bowel movement, that weight will be shed, so this would not be true weight gain, such as fat or lean mass.”

4. You’re just constipated

Essentially, the same thing is going on here as in the point above, but the cause may not necessarily be fiber.

Before you alter your diet or workout routine, make sure you’re adequately hydrated and your bowel movements are on a regular schedule.

5. Your period is coming up

People who menstruate, listen up. “Right before our periods, we hold onto water and ‘gain’ weight, which can be devastating for some women,” Hunnes explains.

And it’s not always as simple as holding some extra water.

Hunnes points out that hormonal shifts can also compel women to reach for saltier foods, which may additionally result in excess water weight from increased sodium.

But it shouldn’t be cause for alarm because, as Hunnes points out, “once we get our periods, the hormone shifts again, leading us to shed that water weight, and the scale will come back down.”

6. You switched to intermittent fasting

Don’t get us wrong: There are plenty of studies that show the benefits of intermittent fasting.

One such benefit is getting to consume larger meals since the eating window is smaller.

But if you just started eating this way and ate a bigger meal than usual, the scale could jump temporarily.

And while several factors on this list may be contributing to weight gain, it could also be something you never considered.

The scale might jump from larger portions “based on the sheer increase in blood volume from large meals,” White explains.

This increase can derive from two sources: water inherent in food and water retained as a result of excess sodium.

7. You had a hard strength-training session

Resistance training can cause microscopic tears in muscle tissue. While that’s a good thing overall because it helps you build muscle, you might not like the effect on the scale the next day or two.

That’s because muscle damage, even if it leads to stronger muscles in the long run, can cause inflammation.

That’s completely normal — indeed, it’s essential to the adaptation process that helps you build muscle and grow stronger — but it can also cause slight swelling that can nudge your number on the scale up a bit.

But don’t sweat it — this extra “water weight” usually goes away in a week or two.

8. You started a new medication

Hunnes and White both note that certain medications can cause your scale weight to increase. You might notice that effect suddenly.

And while whether it stays around differs from person to person, this is something to discuss with your doctor.

If the increase concerns you, talk over your options with your prescribing physician who might know alternatives.