Why the Weight Swings?

Learn why your weight changes throughout the day.


By Erica Schuckies


If you’re among the 75 percent of Americans who weigh themselves at least once a week, you probably know how stressful it can be to see fluctuating numbers in short periods of time. And if you weigh yourself twice in one day, you might be even more confused at the conflicting results. You’re content with what you see in the morning, but getting on the scale again that night could be an entirely different story.

So what does it all mean and how much should you worry about gaining weight during the day? We spoke with two professionals to get the low-down on why these weight swings occur—and how to handle them.

Why the Weight Swings?

According to Kathryn Boling, M.D., a family medicine practitioner in Lutherville, Md., it’s completely normal—and even expected—to see a different weight on the scale from morning to night. While there are a number of reasons for these variances, water weight is the main cause of weight variation.

“During the overnight hours, you have an extended period of time where you’re not eating or drinking, so you will wake up dehydrated,” she says. “Water weight is very heavy. Thus, when you are dehydrated in the morning, you will be at your lowest weight of day. As soon as you start drinking, your weight will slowly start to increase.”

Drinking water and other fluids throughout the day will certainly cause you to see small changes on the scale, but what you eat has a big effect on how much of that water you retain.

“If you’ve had a lot of carbohydrates, you could see a small weight increase during the day,” says Dani Singer, the director of Fit2Go Personal Training in Baltimore. “Many people are on low-carb diets because they think carbs are bad for them. Carbs don’t make you fat, but they do make you retain water.”

Foods high in sodium can also cause water retention, which, depending on how your body metabolizes food, can show up almost immediately on the scale.

But not all scale changes are going to be in the upward direction. Singer notes exercising as a potential cause of seeing a fast weight drop, especially if you sweat up a storm. Before you celebrate too much, he’s also quick to point out that the weight you’ve lost right after a workout is water weight, not fat. As you begin to rehydrate, your weight will likely level back out.

“Exercise would lead to a pretty immediate change because the water is leaving your body as sweat, so you might weigh a pound or so less when you get done with your workout,” he says.

What’s Normal?

Even though weight fluctuations are normal throughout the day, you should expect to see no more than a one- to three-pound weight difference in a 24-hour period.

“If you see a dramatic weight change and your hands or joints are swollen, you might have excessive fluid retention,” Boling says. “This could point to a heart problem, or maybe you’ve gone out of control with your diet.”

She also points to flying on an airplane as a cause of excessive fluid retention, especially with longer flights. Sitting in the same position for extended periods of time can negatively affect your circulation, which leads to fluid collecting at your joints. This not only shows up on the scale, it can also be visible through swelling in your ankles, knees and knuckles.

On the other hand, losing too much in one day is not only unsustainable, it can also be dangerous. Singer tells us that a good rate of weight loss is only one to two pounds per week. Any more than that, and you can risk damaging your metabolism and potentially gaining back the weight you lost (and then some).

So what’s the best way to track your weight loss or weight maintenance journey? Both our experts recommend weighing yourself once a week to avoid relying too much on the small fluctuations that happen during the day. If you must track your weight every day, however, Singer suggests stepping on the scale at the same time, under the same conditions—and in the nude.

“Take your weight every day at the same time and make an average each week,” he says. “This way, you can see if you’re making progress over time.”

Whether you gain or lose during the day, it’s important to remember that the numbers on the scale are just showing a small part of the equation. Consider your diet, your activity levels and how you’re feeling—both physically and emotionally—to keep track of your overall health and wellness.

Erica is a runner, gym rat and outdoor buff based in Austin, Texas. She is a lifelong athlete, having participated in a number of sports from her youth years well into her adult life. Erica has a passion for creating and sharing information, motivation and inspiration to help athletes-in-training across the world. She previously worked as the Running Editor at (find her articles here), where she connected with runners of all levels to help them reach their running and fitness goals. You can follow Erica on Twitter or Instagram.

Main Photo Credit: Rostislav_Sedlacek/; Second Photo Credit: Georgina198/; Third Photo Credit: VectorLifestylepic/; Fourth Photo Credit: David Pereiras/

Dec 18, 2016

Good read.

Jan 8, 2017

A good article 👍🏻