If you're exercising for weight loss, nothing can be more disheartening than stepping on the scale after a workout to discover you've gained weight. But before you throw your hands up in the air and swear off exercise forever, you should know that the gain is temporary. Exercise doesn't cause you to gain fat; eating too much does. There are 3,500 calories in a pound of fat, so you've got to consume a big surplus just to gain 1 pound of fat. If the scale moves in the wrong direction immediately after you exercise, your fluid levels could be the cause.
If you consume more fluids than you sweat out during exercise, you'll notice a gain. For example, say you drank a 20-ounce bottle of water at the gym, but only lost about 4 ounces of fluids from sweat. That 16-ounce surplus of water floating around in your belly would translate into gain on the scale. This isn't unusual as exercise can induce a thirst response. The good news is that water contains zero calories, so as soon as your body flushes out the extra fluids -- assuming you weren't dehydrated before your workout -- that weight will disappear.
Water Retention From DOMS
Water retention can also create the illusion of post-workout weight gain. Delayed onset muscle soreness (DOMS), the muscle pain you experience 24 to 48 hours after an intense workout, could be a factor. DOMS is caused by microscopic tears in muscle fibers that are a part of the muscle growth process. These tiny tears can cause cause swelling in the muscles, resulting in slight fluid retention.
Water Retention From Your Diet
Dietary changes can also cause weight gain from fluid retention. When you exercise, your body may crave more carbohydrates because these are the primary and preferred fuel source for activity. An increase in carb intake, even if you're burning off the extra calories you consume, can cause temporary water retention. As you become more efficient at exercise, your muscles become better at storing glycogen for fuel. While this is a strong indicator of fitness, it can also reflect on the scale. Each gram of stored glycogen holds about 3 grams of water, which can result in a water weight gain of a couple of pounds.
Dehydration and Sodium Intake
Dehydration can also cause water retention. If you're not taking in enough fluids, your body may retain water as a survival mechanism. Excess sodium intake can also cause your body to retain water by altering the natural balance of sodium in the body.
Precautions and Tips
Consult with your doctor before beginning a new exercise program. Slight fluctuations in weight from fluids is normal, but extreme swings can be a sign of serious dehydration or hyponatremia, a dangerous electrolyte imbalance caused by overhydration.
If seeing subtle gains in your weight after exercise bothers you, don't weigh yourself after the gym. Instead, step on the scale first thing in the morning, and don't do it more than once a week. Keep your sights set on the big picture and don't get discouraged from minor fluctuations in your body's fluid balances.
- Nutrition ATC: Exercise Program Can Result in Quick Weight Gain
- Journal of Applied Physiology: Carbohydrate Exerts a Mild Influence on Fluid Retention Following Exercise-Induced Dehydration
- Healthy Times: 7 Ways to Keep Away Fluid Retention
- CNN Health: How Is It Possible for My Weight to Fluctuate So Much?
Jessica Bell has been working in the health and fitness industry since 2002. She has served as a personal trainer and group fitness instructor. Bell holds an M.A. in communications and a B.A. in English.