5 Reasons You’re Gaining Weight While Working Out

You’ve been putting in the effort and exercising regularly. But you’ve noticed something peculiar: When you step on the scale, the number goes up rather than down. What gives?

There are several reasons why you might be gaining weight while working out. The uptick can be frustrating if weight loss is one of your fitness goals. But it’s not usually cause for concern. And a few minor changes to your routine might keep weight gain at bay. Here are five reasons you may be gaining weight even when you’re exercising.

1. Increased muscle mass

Exercising causes tiny tears in your muscle fibers. It sounds bad, but it’s actually a good thing. After your workout, your body works to repair these tears, allowing your muscles to get bigger and stronger.

So even though you may be losing fat, you’re gaining muscle. You might feel slimmer, even as the number on the scale rises.

“The scale doesn’t tell the entire story,” said exercise physiologist Christopher Mohr, PhD, RD. “Since muscle and fat take up different volumes, they look very different on the body.”

But Mohr said that your overall body composition, including body fat, is more important than your weight. It’s harder to measure your body fat, but some smart scales can give you a rough estimate. You can also get a body scan at a sports medicine clinic for a more accurate number.

But none of these measures paints a complete picture of your health and fitness.

2. Postworkout inflammation

Those tiny tears in your muscles can also cause temporary postworkout inflammation. “This is expected and perfectly healthy,” Mohr said. You may retain fluid after exercise as your body repairs the damage, which can cause water weight gain. Any uptick on the scale is usually minor and short-lived.

Weighing yourself regularly can be helpful on your weight-loss journey. But Mohr suggests skipping a weigh-in right after your workout. 

Try to weigh yourself at the same time of day. “First thing in the morning, before exercising, eating or drinking anything keeps things on a level playing field,” Mohr said. Cut back on checking your weight if you find yourself obsessing over the number on the scale.

3. Supplement use

You might think you need supplements to meet your fitness goals. So you put an extra scoop of protein powder in your morning smoothie or grab a preworkout drink on your way to the gym.

But preworkout supplements are not FDA approved, and ingredients vary by brand. Some might have more calories — many of them from added sugar — than you realize. Common supplement ingredients like creatine may also cause temporary water retention.

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Many people don’t need preworkout supplements because they can get plenty of performance-boosting nutrients from a balanced diet. Whole foods should be fine unless you’re an athlete with a rigorous training schedule, or a healthcare professional suggests supplements for a medical condition. This will make it easier to manage your diet and reach your weight and health goals.

4. Workout plateau

Imagine exercising consistently for weeks and seeing a downward trend on the scale. Then your progress suddenly halts, even though your workout plan and diet haven’t changed. This is called a workout plateau. It occurs when your body adjusts to your exercise routine and no longer needs as much energy to support your effort. So you don’t burn as many calories as you did before.

“Plateaus are normal,” said Kevin Huffman, MD, a bariatric physician. “Your body adapts to what you’re doing, so the scale could stall for a week, a month, or even more.”

That doesn’t mean you should give up. But you may need to take on new challenges, such as increased exercise time or intensity. “Change your workout, try some new moves, or tweak your diet just a little to make sure your body doesn’t get used to your routine,” Huffman said.

5. Diet changes

Exercising regularly and eating balanced meals are critical lifestyle strategies for safe and sustainable weight loss.

You can spend hours working out. But if you don’t adjust your diet, you may gain weight. Many weight-loss diets emphasize calorie restrictions that are harmful and hard to maintain. For example, a low-calorie diet can make you lose muscle instead of fat. And less muscle mass could make you regain any weight you lose.

You may feel hungrier after you exercise, so you might eat more than usual. That’s not necessarily a bad thing. But try to limit or avoid processed foods like energy bars, sugary cereals, and soda, all of which can contribute to weight gain.

Finding the right nutrition plan to support your weight-loss goals can be tricky. You may need to lower your daily calorie intake. But you don’t have to track everything you eat, and you shouldn’t try overly restrictive diets. Consider healthy tips to get the calories you need, such as:

• Tracking how your workouts affect your appetite and mood

• Adding more lean protein, fruits and vegetables, and whole grains to your diet

• Reducing processed foods and sweets in your diet

• Using a meal planner to prioritize balanced, nutritious meals

When should you be concerned about weight gain from working out?

Working out in and of itself doesn’t cause you to gain weight. Building lean muscle mass can add a bit to the scale, and that’s a good thing. If something else is causing you to gain weight, such as a change in your diet or overdoing it with supplements, you can readjust and get back on course.

But most experts will tell you to take your attention off the scale and notice other changes that indicate progress. “The most important factor is how you feel,” Huffman said. “Do you feel better? Are you stronger, more energetic? If so, these are great signs that you’re moving in the right direction.”

If you exercise regularly and make other lifestyle changes but keep gaining weight, talk with a healthcare professional. They might provide additional tips or look at other factors that are leading to weight gain. These could include underlying health conditions — such as hypothyroidism — or your medications.

But don’t give up. “Consistency and a whole-body approach to health are the real keys to success in the long run,” Huffman said.

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Written by:

Jody Braverman, CPT, RYT

Jody Braverman, CPT, RYT, has worked as a trainer, yoga teacher, nutrition and lifestyle coach, writer, and editor for over 20 years. She got her B.A. from the University of Maryland and maintains several accredited certifications.

Edited by:

Alex Eastman, PhD, RN

Alex Eastman, PhD, RN, is a California-based registered nurse and staff medical editor at GoodRx, where he focuses on clinical updates and Latino health.

Reviewed by:

Farzon A. Nahvi, MD

Farzon Nahvi, MD, is an emergency medicine physician and author of “Code Gray: Death, Life, and Uncertainty in the ER.” He works at Concord Hospital in Concord, New Hampshire, and teaches at the Geisel School of Medicine at Dartmouth.

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