I’m exercising, so why am I gaining weight?

One of the primary reasons for starting an exercise regimen is to drop a few pounds.  But, what if you have the opposite happening – your weight is going in the opposite direction – up – instead of down.  What is going on?  How can it be that you’re gaining weight while working out?

It is not unusual to have this happen as it is a fairly common incidence among many who have committed to get in better shape.  When you think you are giving it your best shot by exercising more, unfortunately, sometimes the numbers on the scale may not reflect what you think they should.

A 2013 review of scientific studies found a surprisingly large number of people who begin an exercise program subsequently pack on extra pounds.  The study findings showed that most sedentary people who start exercising lose far less weight than expected.  

Several reasons can explain why this happens

The key to remember is not to reduce or quit working up a sweat.  Exercise has several important benefits that improve our health far beyond what you may weigh. Here are some things you should know about why exercise may cause some weight gain:

  • Retention of water after exercise

After a hard workout and sweating profusely, you would think you have lost a few pounds.  But if the number on the scale has gone up, it could be due to water retention that sometimes happens after exercise.  

Some reasons for this can include your body acclimating to exercising in a warmer climate, hyponatremia that leads to fluid retention due to consuming too much water with insufficient sodium intake or consuming too little fluid leading to dehydration where the body attempts to hold on to whatever water it receives. 

Our body weight is approximately made up of 55-70% water.  This percentage can vary throughout the day by several pounds.  Depending on your body composition and what percent water content you are composed of, it can influence and reflect what you will weigh.  But don’t let that discourage or persuade you from getting sufficient exercise regularly.

  • Intake of too many calories

Let’s face it.  Exercise may be increasing your appetite.  When starting an exercise program, your body begins to pump out various hormones making you feel hungry. Sometimes the increase in activity, such as going for a jog or a bicycle ride, may cause you to seek out food once you get home. 

One reason people may not see much weight loss after taking up exercise is they end up eating just as many calories or more than what they burned during the activity.  For example, a 30-minute walk may burn around 100-150 calories.  But if afterward, they make themselves a smoothie containing two to three times that amount of calories, they cancel out all the calories they burned walking.

What can help is to keep a food diary for at least a week or use an online tracking site like Calorie Count to get an idea of what and how much you are eating each day.  To lose weight, you still have to make smart food choices by monitoring calorie intake combined with exercise.

  • Moving less on days you exercise

Exercising most days throughout the week is best but be sure not to turn into a couch potato the rest of the day once your workout is over.    

When we exercise for a certain length of time on any given day, many people will move much less during the rest of the day. Instead of remaining physically active throughout the rest of the day, it is not uncommon for someone to spend more hours sitting on the days they worked out, with them burning fewer total calories.

The idea is to keep busy every day, even after workouts. Add in extra physical activity by taking the stairs instead of an elevator or parking your vehicle farther away from an entrance.  Don’t think that just because you were “good” and walked for 30 minutes, you can spend the rest of the day barely moving.

  • Strength training and weight gain

Lifting weights is an important exercise component everyone should do.  Building and maintaining muscle mass is critical to achieving strength and stamina, improving posture, reducing back injuries and osteoporosis, and improving overall body composition.  

But it is not unusual to notice some weight gain when taking up weight lifting.  When our body composition goes from more dense muscle mass to reduced body fat, the scale may reflect an increase in body weight.  However, an increase in muscle mass means a loss of inches in body measurements and body fat percentage, both worthwhile achievements you will have gained.

The important thing to remember is to not give up on exercise. Weight gain is usually temporary and will correct itself in time.  However, if you are exercising and still gaining weight, it could be your workouts are effective, but you need to make better food choices to achieve better weight loss.  Consider meeting with a registered dietitian who can help you tweak your diet by making a few changes to get the desired results.


Dr. David Samadi is the Director of Men’s Health and Urologic Oncology at St. Francis Hospital in Long Island. He’s a renowned and highly successful board certified Urologic Oncologist Expert and Robotic Surgeon in New York City, regarded as one of the leading prostate surgeons in the U.S., with a vast expertise in prostate cancer treatment and Robotic-Assisted Laparoscopic Prostatectomy.  Dr. Samadi is a medical contributor to NewsMax TV and is also the author of The Ultimate MANual, Dr. Samadi’s Guide to Men’s Health and Wellness, available online both on Amazon and Barnes & Noble. Visit Dr. Samadi’s websites at robotic oncolo gy and prostate cancer 911.

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