Why Exercise Can Cause Weight Gain

Learn why exercise can sometimes cause weight gain and what to do about it.

Ben Greenfield
4-minute read
Episode #77

Listener Macias recently wrote in:

“I've been doing resistance training and some cardio for a couple of months now and I've noticed that I've been gaining weight, mainly around my belly. Do you have any way to explain this?”

In this episode, I’ll answer Macias’s question, explain what kind of things would cause you to gain weight even if you’re exercising, and tell you what you can do if you are gaining weight when you exercise.

Why Exercise Can Cause Weight Gain

Muscle Gain - Muscle gain is the most common reason for weight gain caused by exercising. Muscle is comprised of small dense fibers, while fat is comprised of larger, less dense droplets. This means that even if you lose fat, you may notice a weight gain if you’re simultaneously gaining muscle.

But this is nothing to complain about, since with this weight gain comes a smaller waistline, more definition, and a positive change in your physical appearance! This is a good reason to monitor your body fat, rather than simply track the number of pounds you weigh. Remember: muscle may weigh more, but it takes up far less space.

Stress - When you begin an exercise program or begin to work out more, you may sacrifice sleep, have less time to get important tasks done, and also require your body to be doing much more than it is used to. This can create a perfect storm for a significant stress response.

When you are stressed, your adrenal glands can increase production of a hormone called cortisol. Think of this as your “fight or flight” stress hormone – an evolutionary adaptation that would come in quite handy if you were running from a lion and you needed to increase heart rate, sweat rate, blood pressure, or body temperature.

But if an increase in exercise changes up your schedule and your life to the point where you feel as if you are constantly “running from the lion,” then you may overstimulate your adrenal glands and produce excessive cortisol. By causing you to retain sodium and experience fluid retention, cortisol causes an increase in blood pressure and a stronger contraction of your heart. Since you aren’t running from a lion while you’re sitting at your desk at work, not only do you not really need this constant blood pressure elevation, but you also don’t need all the fluid retention and weight gain that comes with it!

So if you’re constantly stressed, and not taking enough recovery or rest from your workout days, then you can experience weight gain due to fluid retention. The solution is to make adjustments that decrease stress, such as getting to bed earlier, substituting a workout day with a “yoga day,” or rearranging your schedule to make getting to the gym less stressful.

Compensatory Eating - Studies have shown that if you do a hard workout in the morning, you’ll very likely to “compensate” and overeat later in the day. This is the case for two reasons: 1) you feel “entitled” to eat more because you did such a good job exercising and 2) your metabolism is higher and your appetite truly is greater.

Of course, if you’re burning 500 calories with a morning workout, but eating an extra 1,000 calories the rest of the day, then you’re going to gain weight, even if you’re exercising!

Here are some tips to avoid compensatory eating:

  • Eat the majority of your daily carbohydrate intake immediately after your workout. For example, if you exercise in the morning before breakfast, save your fruit, cereal, or “cheat meals” for breakfast only, and eat more appetite satiating fats and proteins throughout the rest of the day.

  • Drink lots of fluids. Often appetite cravings after a workout are due to dehydration, and not a true need for calories.

  • Write down what you eat. The simple act of logging your food can help to keep you from eating calories willy-nilly on your workout days. Similarly, actually having a meal plan for what you’re going to eat for the day can also help you avoid excessive munching.

Ineffective Exercise - Although this can be a frustrating reason for gaining weight when you exercise, the simple answer may be that you’re simply not working out the right way. I most often observe this phenomenon in people who are not exercising at a high enough intensity, only using walking for cardio, not doing weight training, or simply not being physically active every day of the week. To learn whether the workout you’re doing is actually good for weight loss, check out the Best Workout For Fat Loss.

I hope that helps, Macias!

Finally, if your issue is not gaining weight when you exercise, but simply the inability to make that scale actually budge and go down, then you should check out the article How To Get Off A Weight Loss Plateau.

If you have more questions about why exercise can cause weight gain, or your own tips about how to stop weight gain from happening when you exercise, share them in Comments or on the Get-Fit Guy Facebook page!

Scale image courtesy of Shutterstock

About the Author

Ben Greenfield

Ben Greenfield received bachelor’s and master’s degrees from University of Idaho in sports science and exercise physiology; personal training and strength and conditioning certifications from the National Strength and Conditioning Association (NSCA); a sports nutrition certification from the International Society of Sports Nutrition (ISSN), an advanced bicycle fitting certification from Serotta. He has over 11 years’ experience in coaching professional, collegiate, and recreational athletes from all sports, and as helped hundreds of clients achieve weight loss and fitness success.

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