Why Does My Weight Fluctuate So Much? Dietitians Answer

Key Takeaways

You may encounter 1 to 3 pounds of weight fluctuation daily, which is normal. If your weight is fluctuating by more than 3 pounds consistently, you may want to get a medical evaluation.

Weight fluctuations, themselves, may increase a person’s risk of chronic illnesses like type 2 diabetes and can indicate an increased risk of a cardiovascular event by as much as 85%. (1)

Common causes of weight fluctuation include hydration status, sodium intake, bowel movements, stress, menstruation, medication, and illness. 

Weighing yourself daily can make it seem like your weight changes more significantly than it actually does, making less frequent weigh-ins important for gathering meaningful information. It is also important that you weigh yourself in a consistent manner (i.e., before food or water each time).

Weight fluctuation is frustrating, whether you’re trying to lose weight or not. It can make you feel as though your exercise and nutrition protocols aren’t doing what you want them to, or make you feel plain uncomfortable in your own body. While it never feels great to see the scale go up and down, you can breathe a sigh of relief knowing that some level of weight fluctuation is totally normal and nothing to worry about. 

Credit: Pormezz / Shutterstock

I talked with several dietitians specializing in different aspects of nutrition—weight management, eating disorder treatment, and medical nutrition therapy—to sift through the finer details of weight fluctuation. What’s normal? What’s not? How can you minimize it? We answer all of those questions and more—including the biggie, “Why does my weight fluctuate so much?”—in this guide. 

Meet The Experts 

Rita Faycurry, RD, is a registered dietitian at Fay Nutrition specializing in one-on-one medical nutrition therapy and customized nutrition counseling. 

Samantha McKinney, RD, CPT, is a registered dietitian and personal trainer at Life Time Fitness, specializing in metabolism and weight management. 

Emily Van Eck, MS, RD, is a registered dietitian and certified intuitive eating coach specializing in women’s reproductive health and eating disorder treatment.

Gretchen Wallace, MS, RD, CD, is a registered dietitian who specializes in eating disorder recovery and Health At Every Size approaches to nutrition. 

Is Weight Fluctuation Normal?

Weight fluctuation is normal to a certain degree. Our bodies respond to all sorts of factors, such as exercise, food and fluid intake, medication, stress, sleep (or lack thereof), and much more. 

How Much Weight Fluctuation Is Normal?

According to Faycurry, you may encounter one to two pounds of weight fluctuation daily, something that’s not necessarily noticeable unless you weigh yourself every day. And if you do weigh yourself daily?

“Don’t be disheartened; it’s normal,” she says, adding that it’s best to compare your weight week to week instead of day to day to see true changes.

For individuals trying to lose weight, weight fluctuation may be higher in the early stages, which is also normal. “When you start your weight loss journey, it’s normal to lose four to six pounds in the first week,” Faycurry says. “However, your weight loss should average about one to two pounds per week in the span of six months.” 

And if you’re looking to gain weight, the same practice applies, she says: slow and steady wins the race. Trying to lose or gain weight too quickly can result in more weight fluctuation than what’s considered typical

When to Be Concerned About Weight Fluctuation

If you are losing and gaining more than a couple of pounds per day or week, it’s worth looking into. Sometimes, a particularly heavy meal or high alcohol intake can cause you to gain several pounds in a single day. When this happens occasionally, it’s not necessarily a problem. 

But, if you find that your weight fluctuates several pounds each day or more over the course of weeks or months, you may need to analyze your eating habits and/or other lifestyle factors. If you rule out lifestyle factors, it’s a good idea to see a healthcare professional about weight fluctuation.

[Read More: The Fat Loss Myth You Want to Be True: Spot Fat Reduction]

“If a person is losing and gaining the same 10 pounds over the course of months, it could mean that their diet isn’t sustainable,” Faycurry says. “They should ask themselves, is this something I can do forever?” 

Importantly, she continues, “Sometimes weight loss isn’t the answer. Maybe it’s a lifestyle change to remove old habits and behaviors that don’t serve them. If weight loss isn’t achieved, then maybe that’s where their body is meant to be.” 

Factors That Impact Weight Fluctuation

Several factors impact your day-to-day body weight, and not all of them are diet-related. “Some people have irregular bowel movements, consume excessive sodium, drink too much or too little water, or have too many alcoholic drinks,” Faycurry says, and those represent just a handful of factors that influence weight fluctuation. 

Hydration Status 

Drinking water can certainly impact weight fluctuation — hence the common cultural term “water weight.” Being dehydrated or overhydrated can impact your body weight. This can happen acutely or over the long term. 

For instance, drinking 32 ounces of water in a single bout will instantly increase your weight. (Water weighs about 28 grams per ounce, so 32 ounces of water weighs about two pounds.) If you weigh yourself after drinking a lot of water, you might think that you have gained weight in a short amount of time, but the truth is that there’s just a lot of water in your digestive tract. 

[Read More: How To Stay Hydrated While Working Out]

Chronic dehydration, on the other hand, may cause your body to hold onto water to make up for the lack of water coming in. This can alter electrolyte levels in the body, further increasing water retention and creating the illusion of weight gain. As counterintuitive as it may seem, the best fix is to drink more water. (2)

There is a relationship between proper hydration, body mass, and body composition: Individuals who have higher water intake and water balance tend to have more balanced body compositions. (2)

Sodium Intake

Sodium intake is closely related to hydration status. Faycurry explains that your body retains fluids to stay balanced. “If you have excessive sodium intake from food, your body will hang on to fluids to balance the excessive sodium,” she says. “Our body loves to stay balanced to function accurately. You might notice that your rings don’t fit, or your face is swollen or puffy. It’s a defense mechanism your body has, and everyone retains fluid in different places.”

“Overnight weight gain is not body fat, just fluid retention,” she points out. “Reducing sodium can positively reduce weight fluctuation and improve weight loss.”

[Read More: The Surprising Benefits of Salt for Strength Athletes]

McKinney adds that a sodium deficiency, too, can cause weight fluctuation, although she points out that it’s more common in heavy sweaters, endurance athletes, and individuals who are pregnant or lactating. If you’re low on sodium, eating salty foods and/or drinking electrolyte drinks can help bring your body to balance. 

Alcohol Intake

In addition to brain fog, headaches, and fatigue after a night of drinking, you may have also noticed that you feel bloated or puffy. Although evidence around alcohol intake and long-term weight gain is conflicting, consuming alcohol can certainly cause short-term weight changes. (4)(5)(6)

For one thing, alcohol itself contains calories (seven calories per gram of alcohol), so increasing your alcohol intake can push you out of a calorie deficit or past maintenance calories. This may affect your weight if you drink more than usual over a period of weeks. Conversely, cutting out alcohol may help you lose weight quickly in the short term. 

If you feel like you gained weight after one or two nights of drinking, you didn’t. Just like hydration status and sodium intake can cause bloating, so can alcohol intake. 

Alcohol irritates the lining of your stomach, which may cause inflammation and lead to feeling or appearing bloated. Alcohol also leads to dehydration because it has diuretic properties, which in turn can lead to fluid retention. All of this can be exacerbated if your drinks contain high amounts of sodium, such as margaritas with a salted rim. (7)(8)

The best course correction to reduce alcohol bloating? Hydrate and have a nutrient-dense meal that won’t upset your stomach.

Creatine Supplementation

Creatine is a popular sports supplement for its ability to improve athletic performance. However, McKinney says it can cause fluid to move into skeletal muscles. 

Credit: Pixel-Shot / Shutterstock

[Read More: Creatine Benefits All Lifters Should Know About]

While this isn’t a bad thing, she says, (and the performance effects of creatine are nothing to scoff at), it can make the scale weight increase. Usually, water retention from creatine supplementation smooths out over time, and bloating minimizes the longer you take the supplement. (9)(10

Other Nutritional Factors 

Besides water, sodium, alcohol, and creatine intake, still other nutritional factors can affect weight fluctuations, says McKinney. Simply eating food that doesn’t agree with you can cause you to bloat, which may cause temporary weight gain. 

Importantly, “The health impacts really depend on the composition of the weight that’s fluctuating,” she says. “Is it coming from fat mass, muscle tissue, glycogen, changes in weight of waste material based on fiber intake, fluids, or something else? Each one of these would warrant a different response as to how to solve it.”

“You likely don’t need to adjust your diet to minimize weight fluctuations due to normal causes,” she continues, such as minor changes in hydration status or food intake. “Not only is it normal, but it’s expected to see a couple of pounds of variance in your weight from day to day.”

Bowel Movements

Bowel patterns have a role in day-to-day weight fluctuations as well, McKinney says. “For example, traveling can sometimes lead to constipation or diarrhea, causing more or less weight in the body, respectively,” she explains. “The bulk of your stool and amount of water in your digestive tract also varies—and therefore so does your weight—as your fiber intake changes.”

Menstrual Cycle 

Anyone with a menstrual cycle is familiar with how their mental and physical state changes over the course of their cycle. Menstrual patterns influence mood, mental acuity, fatigue, pain, physical performance, and, yes, body weight. 

It’s absolutely normal to gain weight during menstruation, which is mostly due to extracellular water retention, according to a 2023 study in the American Journal of Human Biology. Some research has also found that menstruation increases fluid retention in muscle cells. (11)(12)

Other causes of weight gain during menstruation can come from changes in appetite, leading you to eat more or less than usual or consume more or less salt than usual; a reduced level of exercise, which may influence hydration status; or hormonal fluctuations that lead to gastrointestinal symptoms like constipation. (13)(14)

McKinney says that increases in body weight are typically most significant on the first day of menstruation. Your weight should rebalance within a few days of your period ending.


Several types of medication can cause weight gain or weight loss, including corticosteroids and antidepressants. According to endocrinology researchers at the University of Antwerp, there is a long list of common drugs that can lead to weight gain: (15)

Some diabetes medications, including insulin and thiazolidinediones

Anti-hypertensive drugs, including beta-blockers 

SSRIs, a class of antidepressants


Antipsychotic drugs, including haloperidol and perphenazine


Drugs that can cause weight loss include: (15)

Some diabetes medications, including GLP-1 agonists like Ozempic 

Some antidepressants, like bupropion 

Some antipsychotic drugs, including topiramate and zonisamide

These lists are not comprehensive. If you think that your medication may be causing weight gain, weight loss, or weight cycling, talk to your doctor about the side effects of your medication


McKinney says that if you experience day-to-day weight fluctuations of more than three pounds, you should consider a medical evaluation. This is because high levels of weight fluctuation can point to underlying health conditions or complicate known health conditions. 

For example, “Excess fluid retention can be dangerous with certain underlying medical conditions, such as ascites (in liver disease), high blood pressure, congestive heart failure, and kidney problems,” McKinney says. 

McKinney notes that when she was working in a hospital setting, she saw medical conditions that could cause weight changes of up to 30 pounds in just a couple of days. “Those situations obviously require medical intervention, but I share that example to highlight that day-to-day fluid fluctuations can cause significant shifts to what the scale says,” she explains. 

Thyroid Function 

Thyroid hormones play a major role in weight management due to their role in metabolism and energy management in the body. If your body produces too much of the thyroid hormones T3, T4, and/or TSH (hyperthyroidism), you may lose weight. If your body doesn’t produce enough of any of the thyroid hormones (hypothyroidism), you may gain weight. (16)

If your weight loss or gain is accompanied by symptoms such as rapid heartbeat, anxiety, nervousness, or irritability (hyperthyroidism); or fatigue, feeling unusually cold, dry skin, dry or thinning hair, or depression (hyperthyroidism), consider seeing a doctor to evaluate your symptoms. 


Physical activity can acutely influence your body weight, too. 

“A tough workout causes micro-tears in your muscle, and with proper replenishment from protein and carbohydrate, you may see temporary—and expected—inflammation, fluid shifts, and an increase in glycogen and water storage in your muscles,” McKinney says. 

This would make your weight higher the next day, but all for anticipated reasons that are necessary for your long-term success,” she says.


Weight is also impacted by cortisol, our primary stress hormone, McKinney says. 

[Read More: Ways To Improve Your Workout Recovery When You’re Stressed Out]

“When we are under-slept or experiencing a stressful situation, infection, or injury, cortisol levels can go wonky,” she explains. “As a result, a hormone called aldosterone, which helps regulate sodium and fluid levels, can shift as well, which could cause daily weight swings.”

Eating Disorder Recovery 

Anyone in eating disorder treatment could experience weight fluctuations, says registered dietitian Emily Van Eck, and weight changes are a normal outcome of eating disorder treatment.

“Someone coming into treatment who has been undernourished could gain weight as a result of treatment, but they could also experience initial weight loss,” she says. “If their metabolism had slowed down because of inadequate nutrition, an initial ramping up of metabolism can occur. This is a sign that they need to continue nourishing themselves until they are well into recovery and their weight stabilizes.”

Importantly, treatment plans for individuals with eating disorders need to be individualized with the doctor and dietitian, Van Eck says. “If weight gain is emotionally challenging for a person in eating disorder treatment, this needs to be addressed with the treatment team, including therapy.”

The key, she says, “isn’t to limit weight changes, but to cope with and process emotions related to necessary weight changes.” 

When to Weigh Yourself

This may come as a surprise to many people who are trying to lose or gain weight, but frequent weigh-ins may actually be limiting your success. (17)

“Weighing ourselves, especially weighing ourselves too often, can make it feel like our body is changing more significantly than is actually true,” says Gretchen Wallace, a registered dietitian who specializes in eating disorder recovery. “In the case of weight stabilization, that does not mean that a body won’t fluctuate day by day or week by week but instead that we see the body naturally maintain weight in a small range; sometimes being a little up and sometimes being a little down but overall remaining in a similar place.”

“This can be a sign that the body is giving appropriate hunger cues, that intake is varied and satisfying, that a person is moving their body in ways that are supportive, and that the body is in a weight range that matches what is healthy for their unique genetics and weight history,” Wallace continues.

So, when is a weight-conscious individual to weigh themself? 

McKinney says the best approach is to use averages over time, rather than weighing yourself daily. “Your average weekly weight taken first thing in the morning after a bowel movement over six to eight weeks is way more meaningful than comparing today’s weight to yesterday’s weight.” 

Comparing day-to-day fluctuations to determine whether or not your program is working is incredibly misleading.

— Samantha McKinney

Van Eck points out that there are additional considerations for individuals coping with eating disorders. “I almost always recommend not weighing oneself in the treatment process,” she says. “Taking the emphasis off of the number on the scale and placing it on how things are going and feeling on a daily basis, is a much, much better indicator of progress. Fixating on that number can hinder progress.”

And Faycurry adds that weighing yourself midweek on the same day, at the same time, can help you avoid fluctuations that come with normal weekend activities, such as eating out at restaurants with friends.

How to Weigh Yourself

Interpreting weight changes accurately requires consistent and well-planned weigh-ins.

Credit: Artem Oleshko / Shutterstock

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The following steps can help you create a weigh-in schedule that allows you to minimize recording changes from normal fluctuation factors.

Weigh on the Same Day Each Week

Ideally, you’ll weigh yourself midweek to avoid recording changes influenced by weekend activities. Since drinking alcohol and eating out at restaurants can influence hydration status and sodium intake, give your body a few days to balance out by weighing in on Tuesday, Wednesday, or Thursday each week. 

Weigh at the Same Time of Day 

It’s critical to weigh yourself at the same time each day. The best time to do so is right after you wake up, after having a bowel movement, and before eating or drinking anything. This minimizes factors that affect weight fluctuation.

Weigh Weekly, Not Daily

Experts recommend weighing yourself once per week to avoid recording normal daily fluctuations, which may give you misleading information about the direction your weight is headed. 

Wear The Same Clothes Each Time 

Weigh yourself in minimal, comfortable clothing, such as your underwear and bra or a light T-shirt. A swimsuit is also a good option. Wear the same or similar clothes each time to avoid weight differences from clothing.

Avoid Weighing After Exercise

Because exercise can change your hydration status from sweating, it’s best to weigh yourself before exercising, particularly if you are a heavy sweater or exercising in a hot environment. This also allows you to refuel after exercise without worrying about whether or not it will affect your weigh-in (it will). 

Maintain Hydration for Accuracy 

Stay hydrated daily to keep weigh-ins accurate—and to support your health and well-being. Being dehydrated or overhydrated affects your body weight both in the moment and in the long term. So, make sure you’re drinking enough water daily.

Frequently Asked Questions

Daily weight fluctuation is a common concern for many people. Here are some of the common questions we get asked about people’s wellness journeys.

Is it normal for your weight to fluctuate a lot?

According to registered dietitians, it’s normal for an average adult’s weight to increase and/or decrease by a couple of pounds per day. If you’re losing or gaining more than three pounds on a daily basis—or larger amounts of weight over the course of weeks or months—it may warrant a medical evaluation and/or lifestyle interventions.

How do I stop my weight from fluctuating?

Analyzing lifestyle factors and overall health indicators may help you discover why your weight fluctuates. Water, sodium, alcohol, and fiber intake all influence weight fluctuations. Exercise, bowel movements, stress, menstruation, pregnancy and lactation, medication, and illness also impact your body weight. Minimizing weight fluctuation may require accounting for one or multiple of those factors.

How did I gain four pounds overnight?

Gaining several pounds overnight can be a stressful experience, especially if you’re trying to lose weight. However, it’s likely temporary. You may have gained four pounds overnight because you drank a lot of alcohol, ate a particularly heavy or sodium-rich meal, started your period, or if you need to make a bowel movement. 

What time of day do you weigh the most?

For the most part, your body will be at its heaviest at the end of the day. This is because you’ve eaten meals and snacks and consumed water throughout the day. If you did a tough workout, had a very stressful day, started your period, or consumed a lot of salt, you may weigh more than usual at the end of a given day.

How does the thyroid affect weight gain and weight loss?

An underactive thyroid (hypothyroidism) can cause weight gain, while an overactive thyroid (hyperthyroidism) can cause weight loss, all associated with hormonal changes. Both of these conditions are typically accompanied by a number of other symptoms and usually require medical intervention. (16)

Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.


Bangalore S, Fayyad R, Laskey R, DeMicco DA, Messerli FH, Waters DD. Body-Weight Fluctuations and Outcomes in Coronary Disease. N Engl J Med. 2017 Apr 6;376(14):1332-1340. 

Taylor K, Jones EB. Adult Dehydration. [Updated 2022 Oct 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan

Laja García AI, Moráis-Moreno C, Samaniego-Vaesken ML, Puga AM, Partearroyo T, Varela-Moreiras G. Influence of Water Intake and Balance on Body Composition in Healthy Young Adults from Spain. Nutrients. 2019;11(8):1923.

Wang L, Lee IM, Manson JE, Buring JE, Sesso HD. Alcohol consumption, weight gain, and risk of becoming overweight in middle-aged and older women. Arch Intern Med. 2010;170(5):453-461.

Booranasuksakul U, Singhato A, Rueangsri N, Prasertsri P. Association between Alcohol Consumption and Body Mass Index in University Students. Asian Pac Isl Nurs J. 2019;4(1):57-65.

Fong M, Scott S, Albani V, Adamson A, Kaner E. ‘Joining the Dots’: Individual, Sociocultural and Environmental Links between Alcohol Consumption, Dietary Intake and Body Weight-A Narrative Review. Nutrients. 2021;13(9):2927.

InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Overview: Gastritis. [Updated 2021 Nov 10].

Polhuis KCMM, Wijnen AHC, Sierksma A, Calame W, Tieland M. The Diuretic Action of Weak and Strong Alcoholic Beverages in Elderly Men: A Randomized Diet-Controlled Crossover Trial. Nutrients. 2017;9(7):660.

Wang CC, Fang CC, Lee YH, Yang MT, Chan KH. Effects of 4-Week Creatine Supplementation Combined with Complex Training on Muscle Damage and Sport Performance. Nutrients. 2018;10(11):1640.

Antonio, J., Candow, D.G., Forbes, S.C. et al. Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show?. J Int Soc Sports Nutr 18, 13 (2021).

Kanellakis S, Skoufas E, Simitsopoulou E, et al. Changes in body weight and body composition during the menstrual cycle. Am J Hum Biol. 2023;35(11):e23951.

Sawai A, Tochigi Y, Kavaliova N, et al. MRI reveals menstrually-related muscle edema that negatively affects athletic agility in young women. PLoS One. 2018;13(1):e0191022.

Gorczyca, A.M., Sjaarda, L.A., Mitchell, E.M. et al. Changes in macronutrient, micronutrient, and food group intakes throughout the menstrual cycle in healthy, premenopausal women. Eur J Nutr 55, 1181–1188 (2016).

Guarino M, Cheng L, Cicala M, Ripetti V, Biancani P, Behar J. Progesterone receptors and serotonin levels in colon epithelial cells from females with slow transit constipation. Neurogastroenterol Motil. 2011;23(6):575-e210.

Verhaegen AA, Van Gaal LF. Drugs That Affect Body Weight, Body Fat Distribution, and Metabolism. [Updated 2019 Feb 11]. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000

Liu G, Liang L, Bray GA, et al. Thyroid hormones and changes in body weight and metabolic parameters in response to weight loss diets: the POUNDS LOST trial. Int J Obes (Lond). 2017;41(6):878-886.

Helms ER, Prnjak K, Linardon J. Towards a Sustainable Nutrition Paradigm in Physique Sport: A Narrative Review. Sports (Basel). 2019;7(7):172.

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