In a world where it feels like the weight of your iPhone is more important than the number on the scale, it can be tough to feel confident about your body. In this article, we’re going to explore how much fluctuation you can expect day-to-day and week-to-week, whether or not you have a healthy weight range for your height and build—and what that really means in terms of health. We’ll also talk about things that may affect how much water you retain (hello PMS!), as well as some other factors that could lead to those unexplained pounds coming off overnight. It turns out there are lots of reasons why people might experience fluctuations in their weight—here’s everything you need to know. Is it normal to lose 3 pounds overnight? Read on to find out.
Do You Lose Weight When You Sleep?
If you’re like most people, you probably lose some weight when you sleep—but the amount varies. The majority of body mass is fluid and can fluctuate throughout the day or between individuals, based on a number of factors such as what they’ve eaten and how much water they’ve had to drink. If you’ve woken up 3 pounds lighter, there are two major explanations for it:
You Lost Water Weight
When you wake up, your body needs energy to do things like breathe and digest—just living takes energy. To make this happen, we need to break down our glycogen stores (which were produced after we ate carbohydrates) into glucose molecules that the body can then use as fuel for cells. When there isn’t enough glycogen, we turn to breaking down fat and protein for energy (6).
When we break down these molecules, we produce water—which is excreted through our urine and sweat, which is what causes the weight loss you experience in your sleep. This effect can be substantial if you’re low-carb sleeping or not drinking much water throughout the day.
It’s also possible that you may have had a hormonal imbalance, causing fluid retention and water weight gain (10).
You Lost Carbon Dioxide
When we exhale carbon dioxide (which is a waste product of metabolism), we eliminate it from our bodies by breathing it out (9). Therefore, if you’re sleeping at a high altitude where there’s less oxygen pressure than most places, more of your body’s carbon dioxide gets trapped and eliminated during sleep. If you sleep at a lower altitude where there’s greater oxygen pressure, carbon dioxide is more likely to expand your blood vessels—and the fluid retention that goes along with it.
Can Sleep Help You Lose Real Weight?
Sleep can’t burn calories, which is a prerequisite for weight loss. However, poor sleep can affect various systems and hormones and result in weight gain. Here are several ways poor sleep can hinder weight loss:
Poor Sleep Increases Appetite
Sleep deprivation can lead to increased levels of ghrelin (the hormone that makes you feel hungry) and decreased levels of leptin (the hormone that tells your body it’s full) (11). A study found that just one night of sleep loss caused people to have more ghrelin and less leptin—so they were hungrier (2). And this effect continues as long as a person lacks sleep. Another study found sleep restriction to be associated with increased caloric intake (4).
When we’re tired, our bodies crave sugar and carbohydrates because these foods spike dopamine production. This makes us feel better for a little while but leaves us feeling sluggish, tired, and groggy. If the cycle continues, weight gain is almost inevitable over time.
Poor Sleep Decreases Your Metabolism
When you don’t sleep enough, your body’s metabolism slows down to conserve energy in an attempt to compensate for what it perceives as a food shortage—even if you’re eating normal amounts of food. Research has even shown that people who are sleep deprived have higher levels of insulin resistance than those with adequate sleep (13). Insulin resistance, when left unchecked, can lead to diabetes and obesity.
Poor Sleep Causes Insulin Resistance
Another mechanism at play when trying to understand how poor sleep leads to more body fat is something called non-shivering thermogenesis (NST). NST is what happens when we don’t shiver to stay warm: our bodies naturally decrease their metabolic rate and produce heat through chemical reactions (8).
Among its many functions, this process provides energy for body activity, such as moving. However, NST requires an ample amount of glycogen to function properly (8). This means that those who are sleep deprived risk having their metabolism slowed down as a result of glycogen depletion (12).
Poor Sleep Causes Fatigue
When we are sleep deprived, our circadian rhythm is disturbed which can cause fatigue throughout the day (15). This leads to being tired—and if you’re tired, you won’t feel like exercising (which will result in decreased calorie burn) or cooking for yourself (reducing your food intake).
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How To Get Optimal Sleep For Weight Loss
You can help optimize your weight loss by doing several things:
Reduce Screen Time
Turn off the TV an hour before bed, and restrict phone use right before bed. This allows your body’s circadian rhythm to wind down more easily instead of getting brighter, which stimulates the production of cortisol (a stimulant that interferes with sleep).
Practice Better Sleep Hygiene
Make sure your room is dark, quiet, and cool so you can get better, more restful sleep. And don’t drink alcohol—it’ll only help you fall asleep faster but it will also cause poor-quality sleep and interrupted dreams (leading to fatigue during the day) (1).
Limit Caffeine Intake
One cup of coffee isn’t necessarily bad, but consuming too much can be problematic for your sleep cycle. It takes about 6 hours before half the caffeine in your system is used up—so if you drink a lot of coffee or energy drinks throughout the day, you’re likely to have issues with sleep when it’s time to go to bed (3). Make sure to not drink anything caffeinated after noon.
As little as 15 minutes of daily exercise can help improve sleep quality. But make sure you don’t exercise too close to bedtime or exercise too much in a day, as this can disrupt sleep (5).
Get On A Smart Sleep Schedule
Set a specific bedtime and wake time on your phone alarm. This will help your body’s sleep cycle fall into a pattern that’s in sync with when you’re getting up. Always go to bed at the same time, even on weekends—get rid of the idea that you can “catch up” on missed sleep this way.
Stress is a physiological and psychological response that affects your endocrine system—and if not managed, can cause weight gain. It also causes spikes in cortisol which interferes with healthy circadian rhythms and slows down your metabolism, making weight loss more difficult (7). And extreme stress can even contribute to overeating or binge eating as people mistake their emotional cues as hunger cues (when they’re really anxious) (14).
Develop A Pre-Sleep Ritual
After you’ve started to get on a regular sleep schedule, do a calming activity before bedtime. This will help your body “wind down” so it can fall asleep more easily—and you’ll have better quality sleep with less tossing and turning throughout the night. Try reading fiction or taking a warm bath before going to bed. Avoid stimulating electronics like TV or work projects right before bedtime—it stimulates cortisol production that interferes with the day’s winding down process.
The Bottom Line
You don’t have to stress too much about the occasional overnight weight loss. It’s normal for people who’ve lost water or glycogen to experience it—it’s not a sign that you’re losing fat rapidly. However, getting good sleep will help you lose weight more effectively by regulating hormones that affect your appetite, metabolism, cravings, and energy levels.
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This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!
- Alcohol and Sleep (2020, sleepfoundation.org)
- A single night of sleep deprivation increases ghrelin levels and feelings of hunger in normal‐weight healthy men (2008, onlinelibrary.wiley.com)
- Effects of caffeine on sleep quality and daytime functioning (2018, ncbi.nlm.nih.gov)
- Effects of Experimental Sleep Restriction on Weight Gain, Caloric Intake, and Meal Timing in Healthy Adults (2013, academic.oup.com)
- Evidence of disturbed sleep and increased illness in overreached endurance athletes (2014, pubmed.ncbi.nlm.nih.gov)
- Glycogen Metabolism – Biochemistry (2002, ncbi.nlm.nih.gov)
- Interactions between sleep, stress, and metabolism: From physiological to pathological conditions (2015, sciencedirect.com)
- Muscle Non-shivering Thermogenesis and Its Role in the Evolution of Endothermy (2017, frontiersin.org)
- Physiology, Carbon Dioxide Retention – StatPearls (2021, ncbi.nlm.nih.gov)
- Sex Hormone Effects on Body Fluid Regulation (2010, ncbi.nlm.nih.gov)
- Short Sleep Duration Is Associated with Reduced Leptin, Elevated Ghrelin, and Increased Body Mass Index (2004, plos.org)
- Sleep and Metabolism: An Overview (2010, hindawi.com)
- Sleep disorders and the development of insulin resistance and obesity (2004, ncbi.nlm.nih.gov)
- Stress and Eating Behaviors (2014, ncbi.nlm.nih.gov)
- What Is Circadian Rhythm? (2020, sleepfoundation.org)