When we set out to shed a few pounds, we want those pounds to come from fat. Trouble is, it can be tough to know exactly where our weight loss is coming from—especially at first. Here’s how to tell if you’re losing water weight instead of fat.
Here’s the thing: your body is made up of about 60% water, which means even small changes in hydration can cause the scale to jump around. And while seeing that number drop feels great, you want to make sure you’re actually making progress on your health goals—not just experiencing a temporary shift in fluid levels.
1. You’re On A Low-Carb Diet
Some research suggests that following a low-carb, high-protein diet can be a safe and effective way to lose weight. (By low-carb, we’re talking like 60 grams of carbs per day.) In fact, one study published in the Journal of Pediatrics found that obese adolescents who limited carbs to just 20 grams a day (and increased protein intake) lost more weight in three months than those who limited fat.
Thing is, some of that initial low-carb diet weight loss comes from water—especially if you ate a higher-carb diet beforehand. When we eat carbs, our bodies break them down into glucose. Then, we combine those glucose molecules with water molecules to form a compound called glycogen, which we store in our muscles and liver to use when we need energy later (like during high-intensity exercise). The more carbs we eat and store as glycogen, the more water we store, too.
Here’s what makes this really interesting: each gram of glycogen binds with about 3-4 grams of water. So if you’re storing, say, 500 grams of glycogen (which is totally normal), that’s an extra 1,500-2,000 grams (or 3-4 pounds) of water hanging out in your body. That’s why you can drop several pounds in just a few days when you cut carbs—you’re not losing fat yet, you’re just depleting those glycogen stores and releasing all that bound water.
Until we stop eating carbs, that is. “When we take in fewer carbohydrates, we use up our glycogen stores and release much of that water,” says Alix Turoff, R.D.N., owner of Alix Turoff Nutrition in New York City.
What This Means For Your Weight Loss Journey
If you’ve recently gone low-carb, here’s what you can expect:
- First 3-7 days: Rapid weight loss (often 4-8 pounds) as glycogen and water leave your system
- Days 7-14: Slower, steadier loss as your body shifts to burning fat for fuel
- Week 3 and beyond: A more realistic 1-2 pounds per week as you’re now losing actual fat
The good news? Once you get past that initial water weight phase, the pounds you’re losing are more likely to be from fat. Just don’t be surprised if things slow down after that exciting first week—that’s actually when the real work begins.
Related: How To Eat Carbs And Still Lose Weight
So if you’ve recently gone low-carb, you can expect a few pounds of your weight loss to be from water.
2. You’ve Lost A Lot Of Weight Quickly
Sorry to burst your bubble, but if you’ve lost five pounds after just a week of an intense new diet and exercise plan, most of that is from water, too. Experts typically recommend cutting about 500 calories per day to lose fat at a sustainable rate, which is just about one or two pounds per week, says Turoff. Unless you have a significant amount of weight to lose—like, 100 pounds or more—you can’t really lose more than that pound or two of pure fat that fast.
Think about it this way: one pound of fat equals about 3,500 calories. To lose five pounds of actual fat in one week, you’d need to create a deficit of 17,500 calories—that’s 2,500 calories per day! Unless you’re running marathons while barely eating (which, please don’t), it’s just not happening.
Even if you don’t slash carbs, cutting calories overall still forces your body to use stored glycogen for energy—and as you use it, you release water. That’s why many of us see significant changes on the scale those first few weeks of trying to lose weight, according to the Mayo Clinic.
Rest assured, as your body adjusts to your new eating and exercising throughout those first few weeks, the weight you lose shifts over to be more from fat than water. “Our bodies don’t store an endless amount of water, so once we shed the excess, there’s no more to lose,” says Turoff. “I have many clients who might lose seven pounds the first week or so of a new regimen and then lose one pound per week for the duration of their program.”
Understanding The Timeline
Here’s a realistic breakdown of what healthy fat loss looks like:
- Week 1-2: 3-8 pounds (mostly water weight from glycogen depletion and reduced sodium/inflammation)
- Week 3-4: 1-2 pounds per week (now you’re in the fat-burning zone)
- Month 2 and beyond: Consistent 1-2 pounds weekly, with occasional plateaus that are totally normal
If you’re consistently losing more than 2 pounds per week after that first month, you might actually be losing muscle along with fat—which isn’t ideal since muscle helps keep your metabolism running strong.
3. Your Weight Fluctuates Dramatically Day-To-Day
If your daily weigh-ins have been all over the place the last couple of days, don’t freak out. It’s pretty darn hard to lose and gain body fat overnight, so chances are you’re just dealing with fluctuating water weight.
Research shows that it’s completely normal for your weight to swing by 5-6 pounds in a single day, depending on what you ate, how much water you drank, when you last used the bathroom, where you are in your menstrual cycle (if applicable), and even how much sleep you got. Wild, right?
Think of it this way: If it takes cutting 500 calories per day for seven days to lose one pound of fat, it’s going to take more than one day of eating indulgently to gain a whole pound of fat. In fact, to do so, you’d have to eat about 3,500 calories more than your body needs. If you usually eat 2,000 calories per day, that’s a whopping 5,500 calories!
However, when you drastically change your diet from one day to the next—say, by going from eating zero carbs to eating all the carbs, and back again—you quickly retain and lose enough water to throw off that scale reading.
Common Causes Of Daily Weight Swings
Your weight can jump around because of:
- Sodium intake: Had sushi with soy sauce or Chinese takeout? That extra sodium makes your body hold onto water to maintain proper balance
- Carbohydrate fluctuations: Remember that glycogen-water connection? It works both ways
- Hormonal changes: Especially for women during different phases of the menstrual cycle
- Inflammation: Tough workout yesterday? Your muscles are holding fluid while they repair
- Bathroom habits: This one’s obvious, but it can account for 1-2 pounds of difference
- When you weigh yourself: Morning vs. evening can show a 3-5 pound difference
Related: 11 Smart Ways To Cleanse Your System, Straight From Health Experts
Get back to your usual way of eating and hang tight, and the scale will normalize in your next weigh-in or two, says Noam Tamir, C.S.C.S., owner of TS Fitness in New York City.
The best approach? Weigh yourself at the same time each day (ideally first thing in the morning after using the bathroom) and look at weekly averages instead of getting hung up on daily numbers. Even better, weigh yourself just once a week on the same day at the same time.
4. Your Clothes Don’t Fit Any Better Than Before
Regardless of the story the scale tells you, your clothes will always tell the truth about weight loss. If you’re only losing water, you probably won’t notice much of a difference in how your clothes fit, says Tamir. However, if you’re losing fat—and inches—around your waist, for example, your clothes will feel looser and you’ll know you’re losing body fat.
This is one of the most reliable signs you’re making real progress. When that pair of jeans that felt snug last month suddenly has some wiggle room, or when you need to tighten your belt an extra notch, that’s your body telling you something the scale can’t: you’re actually changing your body composition.
Another way to test whether you’re losing fat or water: Bust out the body fat calipers. These pincers can roughly estimate your body fat percentage, and are an easy way to track your progress. All you have to do is firmly pinch the chunk of skin about an inch above your right hip bone with your fingers, place the caliper over the skinfold, apply pressure until you feel a click, and check the body fat reading on the tool.
Other Ways To Track Real Progress
Beyond the scale and your jeans, here are more reliable indicators that you’re losing fat:
- Take measurements: Grab a soft tape measure and track your waist, hips, chest, thighs, and arms monthly
- Progress photos: Same outfit, same lighting, same pose every 2-4 weeks reveals changes you might not notice day-to-day
- How you feel: Are you sleeping better? Do you have more energy? Can you climb stairs without getting winded?
- Strength gains: Getting stronger in the gym? That’s a great sign you’re maintaining or building muscle while losing fat
- Visual muscle definition: Can you see a bit more definition in your arms or legs? That’s fat loss revealing the muscle underneath
Remember, the scale is just one data point—and often not even the most important one when it comes to understanding your health progress.
How To Make Sure You’re Losing Fat
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Get Enough Sleep
Don’t underestimate the power of sleep on fat loss! After all, research shows that sleep deprivation significantly impacts our hunger and satiety hormones.
Take one small study published in The American Journal of Clinical Nutrition, for example: When people slept for just four hours per night for five nights, they ate 300 calories more per day than they did after sleeping for nine hours per night for five nights. To keep your fat loss efforts humming along, prioritize the recommended seven to nine hours of shut-eye per night.
Think about it: when you’re tired, everything feels harder. Your willpower takes a hit, that donut in the break room suddenly looks irresistible, and the idea of going to the gym after work feels impossible. Plus, lack of sleep actually increases your levels of cortisol (a stress hormone that encourages your body to hold onto fat, especially around your midsection) and messes with leptin and ghrelin—the hormones that tell you when you’re full and when you’re hungry.
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Eat A Well-Balanced Diet
It’s tempting to slash calories and cut all carbs ever out of your life, but this just sets you up for failure in the long-term, says Tamir. You can only white-knuckle it through an extreme diet for so long before your willpower gives out—and that happens a lot faster if you’ve completely slashed carbs and feel too drained to work out.
Instead, fill your shopping cart with high-quality fruits, veggies, meat, poultry and fiber-rich carbs like whole grains and starchy vegetables. Aim to eat a balance of all the macronutrients (fat, carbs, and protein) your body needs and limit your caloric deficit to 500 calories per day, max.
Here’s what a balanced approach looks like in real life:
- Protein at every meal: Keeps you full, preserves muscle mass, and has a higher thermic effect (your body burns more calories digesting it)
- Colorful vegetables: Load up on these—they’re low in calories but high in nutrients and fiber to keep you satisfied
- Smart carbs: Yes, you can eat carbs! Choose whole grains, sweet potatoes, oats, and fruits that give you energy without the blood sugar rollercoaster
- Healthy fats: Avocados, nuts, olive oil, and fatty fish help with hormone production and keep you feeling satisfied
The best diet is one you can actually stick with for months and years, not just a few weeks. That’s how you lose fat and keep it off.
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Lift Weights Regularly
Unlike fat, muscle tissue is metabolically active, meaning it uses energy even at rest, says Tamir. So the more muscle you have, the more calories your body automatically uses per day (a.k.a. the faster your metabolism is).
If strength training isn’t already part of your routine, start by adding two to three full-body sessions per week. To emphasize muscle growth, the American College of Sports Medicine recommends lifting a moderate weight for three to four sets of six to 12 reps, and limiting rest periods to one to two minutes.
And here’s a bonus: when you’re strength training while in a caloric deficit, you’re sending a signal to your body that says, “Hey, we need this muscle, so don’t burn it for energy!” This helps ensure that the weight you’re losing comes from fat stores, not from your hard-earned muscle.
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Support Your Journey With The Right Supplements
While no supplement can replace a solid diet and exercise plan, some might help support your fat loss goals when used alongside healthy habits. Quality protein powders like BodyTech Whey Tech Pro 24 can help you hit your daily protein targets when whole foods fall short. And if you’re strength training (which you should be!), creatine monohydrate can support your performance in the gym, helping you lift heavier and build more metabolism-boosting muscle.
For managing water retention naturally—especially if you’re someone who tends to feel bloated—magnesium might help support healthy fluid balance when combined with adequate hydration. The Vitamin Shoppe offers magnesium supplements in various forms to fit your preferences.
Remember, all Vitamin Shoppe proprietary brands undergo 320 quality assurance steps with ingredient purity and potency verified by independent third-party laboratories—so you know you’re getting what the label promises.
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Stay Consistent And Patient
This one isn’t glamorous, but it’s the most important: real fat loss takes time. While water weight can disappear in days, sustainable fat loss happens over weeks and months. The good news? Once it’s gone, it’s much more likely to stay gone—especially if you’ve built healthy habits along the way.
Focus on small, sustainable changes that you can maintain long-term rather than dramatic overhauls that leave you feeling deprived and miserable. Your future self will thank you.
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