When you first start a new weight-loss plan, it's common for the pounds to seem like they're practically falling off. But as you get further into it, you may notice that your weight loss starts to stall — or you reach a plateau. That's because, initially, you lose water weight, not fat.
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So how can you tell if the changing numbers on the scale are from water weight or fat loss? Aside from regularly getting your body fat measured, there's no foolproof way, but if your weight is fluctuating a lot, or you lost a lot of weight really quickly, that's likely water weight.
On the other hand, if you're slowly losing weight while following a healthy diet and exercise plan and your body is starting to look leaner, it's probably fat that you're losing.
Water Weight vs. Fat
You've probably heard the term "water weight" before, but you might not be entirely sure what it means. The number you see on your scale when you weigh yourself is a measure of every single thing in your body. According to Gabe Neal, MD, a family medicine physician and clinical assistant professor at the Texas A&M College of Medicine, most of the weight in your body comes from water. In fact, he says that it's the heaviest thing besides your bones.
And when you first start losing weight, most of those initial pounds lost are in the form of water. That's because, when you restrict calories, or burn off extra calories through exercise, your body turns to a substance called glycogen for energy. Glycogen is a storage form of the simple sugar glucose and it hangs out in your liver and muscles until you're ready to use it.
But an interesting thing about glycogen is that it holds onto water. In fact, it holds three times its weight in water. According to a September 2015 report in the European Journal of Applied Physiology, for each gram of glycogen in your muscles, you hold on to 3 grams of water.
So, when you use up that glycogen, either through calorie restriction or exercise, you also lose the water. But the inverse is also true. When you replenish your glycogen stores (by eating carbohydrates), you can regain that water weight.
Water Weight or Fat Loss?
That's why one of the major things that points to water weight is frequent fluctuation in the numbers on the scale. If you're sticking to a healthy routine and you're seeing your weight go up and down a lot, that's likely due to water weight. The amount of water your body holds onto depends on many different things — like your hormones and how much water you drank, to name a couple. These fluctuations are perfectly normal, but they can be discouraging.
That's why, in an interview with the American Heart Association News, psychologist Amy Walters, director of behavioral services at Boise's St. Luke's Health System Humphreys Diabetes Center, recommends focusing on the overall trend and not the actual day's number. As long as you're steadily losing a little bit of weight over time, try not to get frustrated if the numbers go up on some days.
Another way to tell whether you're losing water weight or experiencing true fat loss is the time frame. If you lose 2 pounds overnight, it's a pretty good indication that you can attribute that weight loss to water. Most people can lose 1 to 2 pounds of actual weight per week and about 1 percent of their body fat in about a month, according to the American Council on Exercise. So, if you're seeing drops that are greater than that, it's likely from water.
The same is also true for weight gain. If you step on the scale in the morning and you're 3 pounds heavier than you were the day before, you're probably holding onto excess water, which can be caused by a temporary imbalance in your electrolyte and fluid levels. In order to gain that much fat that quickly, you would have to eat 10,500 extra calories on top of your calorie needs, which wouldn't be an easy feat.
Read more: How to Get Rid of Belly Bloat & Water Weight
Weight Loss Without Fat Loss
Another thing to note is that, even if you are truly losing weight and it's not water weight, that doesn't necessarily mean you're losing fat. When you lose weight, you lose both fat and lean body mass (or lean muscle). The American Council on Exercise says that 25 percent of every pound you lose will be in the form of lean muscle unless you're eating a healthy, balanced diet, doing cardiovascular or aerobic exercises and incorporating resistance training.
If you're simply restricting calories, but still eating unhealthy foods, and you don't do any resistance training (or strength training), you may see the numbers on the scale go down, but you're losing a large percentage of muscle too. The Mayo Clinic recommends strength training at least twice per week. This not only helps prevent muscle loss as you lose weight, but can also counteract the natural muscle loss that's associated with aging.
Another advantage is that muscle tissue uses up more energy than fat tissue. That means that, when you have a higher percentage of lean muscle, your body burns more calories even when you're just sitting there. So, incorporating strength training not only helps with true fat loss, but makes it easier for you to lose weight.
Dangers of Water Weight Pills
When you're trying to lose weight, it's normal to want immediate results. That's why many people turn to diuretics, or water-weight pills, to help flush excess water from your body in a short period of time. Diuretics prompt kidneys to filter sodium out of the blood and dump it into your urine. Because the balance of sodium and water in your body is tightly connected and highly regulated, this loss of sodium triggers your body to release excess water to maintain the balance.
The three types of diuretics: thiazide, loop and potassium-sparing, come with risks. If you take a potassium-sparing diuretic, you risk hyperkalemia (high levels of potassium in the blood). Too much potassium in your blood negatively affects the way your heart muscles work, increasing your risk of having a heart attack. On the other hand, other types of diuretics can cause hypokalemia (low potassium levels), causing abnormal heart rhythms and kidney disease if left untreated.
Aside from that, other possible side effects of taking diuretics include:
- Muscle cramps
- Joint disorders
- Hyponatremia (low sodium levels in the blood)
When you're trying to lose weight, it's tempting to want to speed up the process by taking water-weight pills, but it's not worth the risk. Water weight fluctuates from day to day and, while it may provide some immediate gratification to see those numbers on the scale drop, that weight will come back. It's better to focus on living a healthy lifestyle and doing what you can to lose fat, instead.
- Columbia University Go Ask Alice! "Bloating or Water Retention?"
- American Heart Association: "The Pros and Cons of Weighing Yourself Every Day"
- Mayo Clinic: "Metabolism and Weight Loss: How You Burn Calories"
- Texas A&M University Health Science Center: "You Asked: What Is Water Weight?"
- European Journal of Applied Physiology: "Relationship Between Muscle Water and Glycogen Recovery After Prolonged Exercise in the Heat in Humans"
- Mayo Clinic: "Diuretics"
- American Kidney Fund: "High Potassium (Hyperkalemia)"
- Merck Manual: "Hypokalemia (Low Level of Potassium in the Blood)"
- American Council on Exercise: "What Are the Guidelines for Percentage of Body Fat Loss?"
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.