Gaining Weight After Working Out? Here’s Why (2024)

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.

Why Did I Gain 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 often 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.

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.

Studieshave 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.

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 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 gaining weight 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.

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.

Fiber-Rich Foods

Refueling with healthy fiber-rich foods may lead to a temporary 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 a slight increase in weight after your workout, but fiber also decreases colonic transit time to encourage bowel movements and is important for gut health. So this is not a nutrient you should avoid. So how much of a difference can it make?

Plus, a high-fiber diet full of fruits, vegetables, whole grains, beans, and nuts is important to general health has been associated with weight loss in studies, so any slight bump after refueling isn't the whole story.

Increased Appetite

When you begin a new workout routine, it may affect your appetite and lead you to eat more. For example, a study of previously sedentary individuals who did an eight-week resistance training program found that their appetites increased during the training. However, the research is mixed with other studies suggesting a reduction in appetite or minimal affect.

A review found that moderate-intensity exercise tended to delay appetite without any effects on later hunger or food intake. Although, the authors noted that a large variability exists between individuals.

If you find that you're really hungry after a workout, try to drink plenty of water and refuel with nutrient-dense foods that support satiety.

Not Getting Enough Sleep

If you're getting up earlier to exercise without adjusting your bed time or working out in the evening and then subsequently staying up later, sleep deprivation may be the reason you're gaining weight after working out.

Not getting adequate sleep can affect appetite-regulating hormones and can increase appetite and food intake. It may also delay muscle recovery. Try to make sure you are sleeping the recommended seven to nine hours per night to feel your best.

Should You Worry About Gaining Weight After Working Out?

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.

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.