Why You Might Be Gaining Weight After Working Out

Woman lifting heavy weights

Verywell / Amelia Manley

There are several research-backed reasons why you might notice a slight weight gain after exercise. These include muscle gain, water retention, post-workout inflammation, supplement use, or even undigested food. In most cases, post-workout weight gain is temporary. Here is what you need to know about gaining weight after working out.


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Why You're Gaining Weight After Working Out

Gaining weight after working out is likely due to muscle fiber inflammation, muscle glycogen and water weight gain, and over time, muscle mass gain. If weight loss is your goal, seeing an increase on the scale when you've been making an effort to exercise can be frustrating. However, it is a normal, common occurrence that is likely temporary. Here are some of the reasons why it might be happening to you.

Muscle Weight Gain

You will likely gain muscle when you start working out. How much muscle you gain depends on your diet and the type of workouts you do. But any increase in physical activity is likely to produce at least some improvements in strength and muscle mass.

If you participate in strength training workouts and consume adequate protein, you're likely to see more significant increases in muscle mass. Genetics also play a role in the amount of muscle mass you gain when starting an exercise program.

If you tend to gain muscle easily, consider yourself lucky. Muscles help to shape a strong, healthy body. Some people put on muscle more quickly than others. But when you gain muscle, the number on the scale is likely to increase.

In fact, even if you're also losing fat, you may see an increase on the scale. Muscle is more dense than fat, but it takes up less space. That means if you gain muscle, your scale weight may go up even as you're losing body fat.

If you've been working out regularly, it's possible for you to lose inches even if you're not losing weight. A higher number on the scale could mean that you are losing fat while gaining muscle—a positive trend that leads to a leaner, stronger body.

Water Weight Gain

Water retention is a common cause of temporary weight gain. Pre-menopausal people are especially prone to body-weight fluctuations throughout the month due to hormonal changes.

If you have periods, you may notice some degree of bloating immediately before and during your period. Exercise can help reduce pre-menstrual symptoms, so it's helpful to keep up with your workouts, though you may still see an increase on the scale.

Studies have shown that fluid retention peaks on the first day of menstrual flow. It is lowest during the mid-follicular period (the middle phase of your cycle) and gradually increases over the 11 days surrounding ovulation.

The degree to which you see an increase on the scale varies from person to person, but at least a slight increase in weight—even after exercise—is normal.

Another common reason for water weight gain is increased sodium intake. Consuming high-salt foods ​can cause an increase in body weight.

Studies have shown that after eating salty foods, most people increase water intake, but do not necessarily produce more urine. The extra fluid in the body adds up to pounds on the scale. Some people are very sodium-sensitive and may retain more water.

Keep in mind that even if you aren't adding salt to your food, it may still be lurking in the processed foods and beverages that you consume. Even some healthy, nutrient-rich foods like soup, cottage cheese, and canned beans may contain excess sodium.

Post-Workout Inflammation

Your workout itself may be causing weight gain—at least temporarily. But this increase may indicate that you are exercising hard enough to see actual results.

Very simply put, exercise (especially weight training) damages muscle tissue. The repair process after exercise allows muscles to grow and get stronger. But in the meantime, inflammation occurs in the tissues.

Exercise physiologists call this exercise-induced muscle damage (EIMD). EIMD is a temporary phenomenon that occurs after new or exceptionally challenging exercise patterns.

Exercise causes structural damage to myofibers (cells in muscle tissue); inflammation results due to a build-up of white blood cells in the damaged tissues. This inflammation and build-up of fluid may show up as temporary weight gain after a workout.

How do you know if your body is experiencing EIMD? You may feel delayed-onset muscle soreness, also called DOMS. You're likely to feel increased soreness the day after or even two days after your workout as a result of the inflammation and repair that is happening in the body.

Supplement Use

Post-workout nutrition or supplement use may also cause a certain degree of weight gain after working out. Exercise—particularly prolonged endurance exercise like running or cycling—depletes the body of glycogen.

It's very common for trained athletes to consume post-workout supplement beverages that contain carbohydrates. Carbs help to restore muscle glycogen. But for each gram of glycogen stored, the body retains three grams of water.

The result? An increase in stored water and possible water weight gain following your workout. Of course, this post-workout effect doesn't just apply to carbohydrate supplementation.

Even carbs that you consume in meals and snacks following your workout will be stored as glycogen with water. This is a normal and healthy process of recovery—so it is not something you should try to avoid.

Other supplements can also cause post-workout weight gain. Creatine, a supplement used by many avid exercisers, may cause weight gain by increasing muscle mass or fluid retention.

Creatine has been studied extensively throughout the years. Evidence has been mixed regarding its effectiveness, but some early studies indicated that creatine supplementation could increase body mass and total body weight. Research scientists surmised that these increases were due to increased water retention.

More recent studies have investigated creatine's potential to increase muscular strength and muscle mass, with some evidence showing that it may provide a benefit. However, the mechanism by which it provides this benefit is not fully understood.

Undigested Fiber-Rich Food

If your workouts make you hungry and you are refueling with healthy fiber-rich foods, the nutritious food you consume may lead to an increase in the scale as it works its way through your body.

Fiber aids in water retention in the colon and results in stools that are less dry and easier to evacuate. Insoluble fiber, in particular, is known to increase stool weight.

Before the stool is passed, you might notice an increase in weight after your workout, but fiber also decreases colonic transit time. So this is not a nutrient you should avoid. So how much of a difference can it make?

In one research study, investigators found that you might produce 125 to 170 grams of stool per day—or about a half-pound.

However, other studies report average daily stool weight to be roughly 106 grams per day—less than a quarter-pound. Still other sources say that your body may produce up to one ounce per day for every 12 pounds of body weight.

Should You Worry?

In many cases, there is no reason to worry about an increase in weight after exercise. In fact, if the weight gain is the result of one of the common causes listed above, you should take it as a sign of success.

Of course, there are other reasons that you may see an increase on the scale. Some medications may cause weight gain, or your calorie intake may have increased along with your hunger levels after exercise.

It may be helpful to use methods other than the scale to measure your workout progress to figure out if changes if warranted.

Most basic bodyweight scales can't tell you if weight gain is due to increased fat, muscle mass, or water retention. To measure actual fat loss, you can regularly use a body fat scale (which are typically not very accurate), or take measurements at different areas of the body. (If you're losing inches, you're likely on the right track.)

But there are also benefits to not focusing on the numbers when measuring your progress toward your weight loss goals. How you feel mentally and physically, how your clothes fit your changing body, and your overall strength and health are all essential parts of the process, too.

A Word From Verywell

Exercise provides countless physical and mental benefits. If you've started a workout program and you're sticking to it, you're likely to experience increased energy, a greater ability to move through activities of daily living with ease, and improved fitness levels. You're also likely to gain a boost in pride and confidence. These are real benefits that should take priority over the numbers on the scale.

Suppose you've measured yourself in different ways and feel you really are going in the wrong direction. In that case, you can work with a qualified trainer or registered dietitian or talk to your healthcare provider to see if there are other reasons for weight gain after your workouts. But in many cases, it's simply a sign that you're doing things right.

Frequently Asked Questions

  • How much weight do you gain after exercise?

    How much weight you gain after exercise depends on your current body composition and weight, carbohydrate intake, overall nutritional status, and type of exercise. A weight gain of 1 to 3 pounds is considered normal, but it could be more or less.

  • How do you avoid gaining weight after exercise?

    You may not be able to avoid gaining weight after exercise. This temporary weight gain is a result of many beneficial processes that will improve your health and body composition in the long run. For instance, the inflammation that occurs post-workout will help build stronger, larger muscles. Excess glycogen storage in your muscles will make you weigh more, but also makes your muscles appear larger without added fat gain.

  • How much weight will you gain after starting a new exercise program?

    How much weight you gain after starting an exercise program depends on your current body composition, calorie intake, and type of exercise you are doing. If you are hoping to gain weight, a strength training program will help so long as you are consuming a diet higher in calories than you burn through activity.

  • What exercises will help you gain weight?

    Exercises that will help you gain weight include strength training movements such as squats, deadlifts, bench presses, rows, and shoulder presses. Building muscle mass with strength training will help you gain weight so long as you are also eating more calories than you burn.

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By Paige Waehner, CPT
Paige Waehner is a certified personal trainer, author of the "Guide to Become a Personal Trainer," and co-author of "The Buzz on Exercise & Fitness."