You Didn’t Gain 3 Pounds Overnight; Weight Fluctuations Explained

Suzie Glassman

What you should know when the scale makes you say hmmm

It’s that time of year when millions of us renew our focus on health and lifestyle changes we want to make for the coming year. Whether you choose to go on a diet, start exercising, exercise more, or some combination of new habits, the start of a new year is a great time to approach your goals with enthusiasm and vigor.

As with any goal, you’ll need to measure your progress. For those interested in losing weight, the bathroom scale often becomes a torture device — one that can make or break your day in a matter of seconds.

As a fitness coach, I ask my clients to weigh themselves daily. I like to see how their bodies respond to various stressors like training and sleep and to changes in calorie consumption. Plus, research generally agrees daily weighing leads to greater weight loss than less frequent weighing.

One study found a group of subjects who weighed daily for six months lost, on average,13 more pounds than those who weighed less frequently. The daily weighers reported adopting more weight control measures due to constant feedback from the scale.

Yet, weighing every day can come with a host of panic moments if you don’t understand the factors at play when your weight bounces up. I’ve received countless frantic emails from clients wanting to know how they could possibly gain three pounds overnight after a solid week of losing.

Seeing the scale go up, even when you’re doing everything right, can make you want to slam it against a wall or throw it in the nearest trash bin, but there are perfectly reasonable explanations as to what’s happening. Knowing what makes your weight fluctuate will allow you to remain calm on your “off” days and help you learn more about your body. I’ll explain how.

What it Takes to Lose/Gain a Pound of Fat

When the scale goes up, it’s natural to believe we’ve gained fat. Forget physics and the laws of thermodynamics. I’ve been there —all logic goes out the window when we see the scale jump several pounds from one day to the next.

However, it’s important to remember we lose and gain fat and muscle at relatively slow rates.

The Personal Training Development Center (PTDC) writes,

To gain 1–3 pounds of fat would require 3500–10,500 calories over what they burn each week, which equates to 500–1500 calories over per day.

While it’s possible to eat that much (I can consume my weight in chips and queso), if you’re sticking to your diet and being mindful of what you eat, it’s doubtful. When the scale jumps 2–5 pounds (or sometimes more) overnight, I can assure you fat isn’t the culprit. So what’s going on here?

The Role of Glycogen

Glycogen is the stored form of carbohydrates in our muscles, and carbs are notorious for messing with weight. Each gram of carbohydrate carries 3–4 times its weight in water (hence the word hydrate in the name).

Say you go out for Italian food, devour the bread basket and eat a bowl full of pasta. You may end up weighing more in the morning simply because your muscles are storing more glycogen. The same phenomenon happens in the opposite direction when eating low-carb.

You can drive your muscle glycogen fairly low by eating a low-carb diet. In 1992, a study published in the American Journal of Clinical Nutrition showed how glycogen loss provides an illusion of weight loss that isn’t real.

The researchers put 11 female volunteers on a very-low-carb diet for four days. From an average starting weight of 196 pounds, the average weight loss was 9.5 pounds. That included 415 grams of glycogen (about one pound); the rest was water.

This is why the ketogenic diet can be so frustrating. Even look at a bagel, and you’ll see an increase on the scale the next day (kidding, but if you’ve tried this diet, you likely know what I mean).

Sodium and Water

Our total weight includes the amount of fat, muscle, bones, organs, and fluid we carry. People tend to forget the amount of fluid in our bodies can vary greatly from one day to the next. If you’ve ever weighed yourself after a night of drinking and waking up to a hangover, you may be shocked to see weight lower. Your sudden weight loss is because you’re dehydrated (a fact I know from personal experience).

What happens after a particularly salty meal? Let’s take those chips and queso I love so much. They’re loaded with salt. Excess salt causes our body to retain water to keep our electrolytes in balance.

If you’re waking up to a higher number on the scale, ask yourself if you ate more salt the day before. If you habitually eat a lot of sodium, it won’t make a difference. But say you normally eat around 2,000mg, and the day before, you had around 6,000mg. That’s enough to cause a spike in weight from extra water retention.

Stomach Contents

The amount of food in your stomach when you weigh is often overlooked as a factor in making the scale go up. Anything left undigested or digested but sitting in your gut can cause big swings in your weight.

Did you eat later at night? Did you weigh yourself earlier in the morning than usual? The amount of time since your last meal will make a difference. I have clients weigh first thing in the morning without clothes after using the bathroom. The idea is to weigh in the same semi-dehydrated state from day to day, but that doesn’t mean it’s always under the same conditions.

Also, resist the temptation to weigh yourself multiple times throughout the day. I’ve seen people gain as much as 8 pounds in a day only to weigh within a decimal point of their previous morning weight. What’s going on there? Again, factors like bowel movements, food volume, sodium, and liquids affect your scale weight.

Stress and Cortisol

The PTDC states,

Cortisol causes water retention (through cross-reactivity with the aldosterone receptor), meaning that elevated levels can mask fat loss.
It just so happens that dieting and exercise both increase cortisol.
Typically, a bigger calorie deficit and more total exercise (usually cardio) will increase cortisol to the point where weight loss becomes erratic and unpredictable.
But things like lack of sleep, big lifestyle stresses, and injuries can also raise cortisol.

What to do about it? Try to resolve the stress. If you’re training super hard, eating low calories, and not losing weight, try adding more rest days and see what happens. Make sleep a priority. I’ve seen clients finally drop weight after several nights of lengthy, high-quality sleep.

How to Manage the Stress of Weight Fluctuations

Your weight from one day to the next means far less than your overall trend. Luckily, there are several great apps that take the guesswork out of whether your weight is trending up, down, or staying the same.

I have a Withings scale that shows my trend like this (during a period of focused fat loss)

Author screenshot

One spike put me almost back to my starting weight, but I didn’t get discouraged because my overall trend remained down. Other apps like Happy Scale can also do the mental math for you.

Bottom Line

Can weighing daily be an exercise in frustration? Absolutely. However, once you understand the factors at play, you can learn how your body reacts to various situations.

You may notice you’re especially sensitive to sodium or that eating later at night causes the scale to go up the next day. Most women will see a spike in weight around their monthly period. Soreness after a workout can also cause an increase.

Knowledge is power, and the scale is just one data point. You can always use other progress indicators like measurements, photos, and how your clothes feel on days when the scale is not your friend.

Play the long game when it comes to weight loss. Slow and steady wins the race. The next time the scale jumps three pounds overnight, tell yourself there’s no way you gained fat that quickly and happily move on with your day.

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I write about health and fitness with the goal to help you live a healthier, happier life.

Denver, CO

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