How to Tell if Weight Is Water Weight or Fat Weight

Stepping onto the scale causes anxiety for many people. You may be even more upset if your weight jumps several pounds in less than a day, and you have no idea what caused it. Water weight fluctuations throughout the day are common, but you may wonder when it's fat weight gain or just water weight.

You can lose 2 pounds of water weight in a day. (Image: ilarialuciani/RooM/Getty Images)

Water Weight

If you've gained a significant amount of weight over a few days to a few weeks, it's most likely water. In fact, it's normal for your weight to fluctuate 2 to 4 pounds over the course of a day due to shifts in your body's fluid status. The extra fluid can last a few hours or a few days. You may be retaining water for a number of reasons, including the weather -- you're more likely to retain water when it's hot -- premenstrual symptoms, lack of dietary protein, or as a side effect of various medications.

Fat Weight

Fat weight, on the other hand, takes several weeks to show up on the scale, according to registered dietitian Monica Reinagel. Eating more calories than your body burns causes fat weight gain; every 3,500 calories you eat above your needs causes a 1-pound weight gain. It doesn't matter where the calories come from -- whether they're from healthy sources or unhealthy sources. However, foods high in fat and sugar, such as fast food, cakes, cookies, soda and chips, are a concentrated source of calories and offer no nutritional value, and researchers report a strong association in a diet high in these foods and weight gain, according to a 2006 study published in Obesity.

Shedding Water Weight

As long as you don't have an underlying medical problem, you can lose water weight fairly quickly by making a few tweaks to your diet. Start by limiting your intake of foods high in salt, such as chips, fast food, frozen dinners and snack foods. Also, don't add any extra salt to your food during cooking or at the table, which includes the salt shaker, along with soy sauce and salty seasonings.

Eat more potassium-rich fruits and veggies such as bananas, oranges, spinach and tomatoes. Potassium helps your body get rid of excess sodium, which can help you shed some water weight. Make sure you're drinking enough water, too, because a well-hydrated body is less likely to hold onto fluids. Aim for 8 to 12 cups a day, says Clemson Cooperative Extension.

Losing Body Fat

Fat weight is not as easy to lose as water weight. To lose a pound of fat, you need to create a deficit of 3,500 calories. Decreasing your usual intake by 250 to 500 calories a day can help you lose 1/2 pound to 1 pound in a week. Exercising to burn calories also helps you lose fat.

You may be able cut calories by making a few dietary changes. For example, swap your 2-percent fat milk for skim milk in your morning cereal and save 30 calories per cup. At lunch, top your salad with tangy balsamic vinegar instead of your usual Italian dressing and save another 20 calories. Snack on a banana instead of your usual chocolate peanut cups during your afternoon break and cut out 127 calories. Satisfy your sweet tooth after dinner with a bowl of fresh strawberries instead of a bowl of strawberry ice cream to reduce your intake by another 200 calories.