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Why Does My Weight Fluctuate?

Learn how weight fluctuation is natural and how to make sure that you don’t panic when it does.

Weight Fluctuation: Is It Normal?

Have you ever stepped on the scale and wondered, “I’ve gained three pounds? How did this happen? What do  I do? These panicked questions from my clients underscore a mistaken belief that they’ve done something wrong, when the truth is that weight fluctuations are normal. Whether it’s due to dehydration, hormonal changes, or water retention, body weight isn’t static but instead changes over the course of the day. 

In short, these natural variations are nothing to panic about. But you’re not alone if you need reassurance.

Why Weight Fluctuates

Let’s get this out of the way right from the top: there is no such thing as a perfect body, or a perfect weight. Numbers on a scale are merely guideposts as we seek to improve or maintain good health, and those numbers have no bearing on your worth in this world. It’s one thing to know that intellectually, and another to remember this when you see fluctuations in your own body weight reflected on the scale — rather than spinning up a perfectionist “all or nothing” mindset which can never truly support a healthy body.

"Your weight fluctuates when your body is doing its job of keeping you alive."

Your weight fluctuates when your body is doing its job of keeping you alive. For instance, there’s a constant exchange of substances at a cellular level, not to mention the work your organs are doing. Other causes for weight variations include water retention, the fullness of your stomach and bladder, medications you may be taking, alcohol consumption, and your menstrual cycle. Maybe you’ve consumed more salty foods, foods heavier in water — like fruits and vegetables — or a lot of carbs, and so the number on the scale naturally shows a temporary increase. As your body processes these foods, that number will readjust to normal. 

The same goes for water retention based on where you are in your menstrual cycle; it’s not unusual to gain a few pounds before you start your period, or to experience bloating, food cravings, or gastrointestinal issues, all of which can affect the number on the scale. You might be dehydrated, which can paradoxically show up as a temporary weight increase as your body tries to retain more water. Your body weight can fluctuate with exercise, due to inflammation and microtears in your muscles that your body then rebuilds as you grow stronger. Skipping your workout can also show up on the scale.

Another surprising factor that influences body weight is fatigue, with studies showing that less sleep can be associated with heavier bodies. Worried about putting on weight literally overnight? While it is technically possible to gain weight in a single day, remember that you’d need to consume an extra 3500 calories to create a single additional pound. So if today’s numbers look different than yesterday’s, it’s more likely that your body’s natural processes are at work.

How Much Is Normal?

Its not unusual for a woman’s body weight to fluctuate up to five pounds in a day, on average, with the body naturally a few pounds heavier at night than in the morning. Your body weight falls into a natural range that changes over the course of the day and with the factors mentioned above, and no two bodies are the same. If you’re trying to track your weight, your best bet is to weigh yourself under consistent conditions each time — like the same time of day, wearing the same (or no clothes), and using the same scale. (More on this below.)

With practice, you’ll learn to take these natural fluctuations in stride. There’s no need to panic, or to subject yourself to a starvation diet in response to small changes. Only a change of more than six pounds or so, especially when accompanied by other symptoms like shortness of breath or swelling, should be a cause for concern and worth a call to your doctor.

Our Own Worst Critics

While you may be watching the scale, there’s an excellent chance no one else will detect a change in your body at all. Researchers at the University of Toronto found that only after a BMI shift of 2.93 is weight loss visible in someone’s face — which means the average person would need to gain or lose about 8 or 9 pounds before it would be noticeable in their face.

This means that, even when the numbers are changing on the scale, it may take a week or longer for weight loss or gain to be noticeable to others. You’ll probably be able to see the difference much sooner, however — like changes in your stomach and legs — and sometimes even before you notice a shift in how your clothes fit.

How to Track Progress without Worry

Now that you know that weight fluctuations are natural, how much of a fluctuation is normal, and that basically nobody will be able to tell anyway, you might be wondering how you can track your progress without additional worry. It can be tempting to step on the scale multiple times a day, but daily fluctuations mean you won’t be getting an accurate read — and you might end up reacting to a “problem” that doesn’t actually exist. It’s also necessary to remember that your overall health is what’s really important, versus a targeted number on a scale.

"The good news is that by setting consistent habits, you can use a scale or other tools to keep track of your progress."

The good news is that by setting consistent habits, you can use a scale or other tools to keep track of your progress. Setting a schedule for weigh-ins — like first thing in the morning, after using the bathroom, without clothing or in just your underwear — is a good way to track progress over time, whether you’re taking measurements daily, weekly, or even every several weeks. Make sure you’re using the same scale each time — one that’s accurate and placed on a rigid and level surface.

Keep in mind that if you have a history of disordered eating, any interaction with the bathroom scale could have a negative impact. If you’re feeling any stress or anxiety around stepping on the scale, a conversation with a supportive therapist might be in order. Plus, a bathroom scale can measure only so much, and it may not register simultaneous muscle gain and body fat loss, because weight changes aren’t usually distributed evenly through the body.

Other measurement methods include regular checks of your body composition to determine muscle, fat, and water content so you can gauge changes over time. You can use a tape measure at home to measure your waist, arms, hips, chest, and thighs. And there’s the tried-and-true method of simply noticing how your clothing fits from one week to the next. To monitor overall health, you can track your heart rate when you’re at rest and during and after aerobic activity.

Sound advice is to be patient and practice kindness with yourself and to keep your expectations realistic when you’re looking for changes in body weight and composition. Striving for perfection is often what causes us to fall off track, but every body is different and how and when your weight loss shows up will be unique to you.

Clinical Psychologist, Dr. Sera Lavelle, is the cofounder of Bea Better Eating and owner of NY Health Hypnosis & Integrative Therapy in NYC. To learn more about Bea Better Eating and our mission, please click here.

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