Why Do Some People Gain Weight After Starting a Workout Program?

You start a new exercise program with dreams of changing your body. When you step on the scale a week later, you see results ― but the numbers aren’t exactly moving in the direction you wanted.

That’s right … after all that sweat equity, your new workout routine led to you GAINING weight. How in the world is that possible?

As it turns out, a slight weight increase is typical as you begin a new fitness journey. To explain why you might add a few pounds (at least temporarily), we turn to physical therapist Gary Calabrese, DPT.

Why you might gain weight after working out

Your body goes through changes as you begin an exercise routine. It’s part of a natural physiological process as you begin putting more demands on your muscles, says Dr. Calabrese.

Here’s how that new workout can bring added pounds.

Inflammation

Exercise puts stress on your body that can lead to small micro tears (also known as micro-trauma) in your muscles. In response to the damage, your body activates its internal repair system to trigger inflammation.

“Basically, your body retains fluid around the micro tear to try to heal it,” explains Dr. Calabrese.

Water has weight, of course, which is why this healing mechanism can add pounds after a challenging workout.

The good news? The inflammation (and extra weight) typically disappears within a day or so, according to Dr. Calabrese. Plus, your “repaired” muscles come back stronger to help you make fitness gains.

‘Power’ storage

If you’re working out more, you’re going to need extra energy ― and those power reserves can show on the scale at first.

Glucose is the fuel your muscles use for energy. When you start to exercise more regularly, your body keeps reserves of glucose (in the form of glycogen) in your muscles to answer the call the next time you work out.

Glycogen binds with water as part of the process, which can add 1 to 3 pounds of initial water weight gain.

The effect, however, is short-lived and should end in a few weeks to a month.

Increased hunger

Exercising can make you REALLY hungry. But while it’s important to refuel after a workout, it’s also possible to overdo it when you hit the kitchen to grab a bite, cautions Dr. Calabrese. A few minutes of munching can easily lead to you consuming more calories than you just burned.

The solution? Put as much thought and effort into your post-workout snack as you put into your exercise session. Focus on eating proteins and nutritious foods that will fill you up and leave you less likely to grab a less-than-healthy option later.

More muscle mass

As you exercise and build muscle, don’t be surprised to see a trimmer you in the mirror but a larger number on the scale. The reason? Muscle is denser (meaning a lot less fluffy) than fat, says Dr. Calabrese.

Put another way, 10 pounds of muscle takes up a lot less space than 10 pounds of fat.

So, as you start working out regularly and building strength, the new muscle you build may eventually weigh more than the fat you’ve burnt off. (Learn more about muscle weight vs. fat weight.)

It often takes at least a month or two to add enough muscle to tip the scale, so don’t be surprised if it happens.

Know this, too: Muscle burns more calories for you, which will pay off in a leaner and more fit body in the long run. (Ten pounds of muscle burns 50 calories a day at rest while 10 pounds of fat burns 20.)

Final thoughts

When you start a workout program, don’t fixate on your scale to determine the effectiveness of the new exercise for you. That’s often NOT the best measure of whether you’re making healthy changes.

Talk to your healthcare provider, physical therapist or athletic trainer if you have questions about changes to your body, too. They can help you map out your progress.

“The key point here is that weight and muscle mass changes will occur,” states Dr. Calabrese. “You may gain a little weight at first, which isn’t what some people see as headed in a positive direction. But stick with it, because you’ll eventually see the long-term benefits.”