How Swimming Can Make You Gain Weight (Easy Explanation)


Swimming is one of the premier calorie burning exercises out there, yet some people have actually reported gaining weight after beginning a swimming regimen. Is it actually possible for swimming to cause weight gain, and, if so, how does it happen?

Swimming can cause weight gain by misleading a person into thinking they burned more calories than they did, causing them to overindulge post-workout. A significant gain in muscular mass due to the resistance of swimming may also increase weight.

These are the two leading explanations for why some swimmers actually end up gaining weight rather than losing weight. In the subsequent sections, we’ll delve into more detail about these two causes of weight gain in swimmers. We’ll also address whether the majority of swimmers gain weight or lose weight over time and exactly how swimmers should go about avoiding putting on extra pounds.

Ways that Swimming Can Cause Weight Gain

To start off, we’ll first analyze the major culprit of weight gain in swimmers: overindulging post-workout. Then, we’ll move on to how muscular growth tips the scales afterwards.

Can Cause You to Overindulge Post-Workout

Although an intense swimming session does burn a meaningful number of calories, many people overestimate how many calories they burn over the course of their workout.

To give you some realistic perspective, the table below provides the average calories burned for a one hour-long freestyle swimming workout. The amount of calories burned directly varies with intensity and body weight (source):

Body WeightCalories Burned at Low IntensityCalories Burned at High Intensity
130 lbs413 cals590 cals
155 lbs493 cals704 cals
180 lbs572 cals817 cals
205 lbs651 cals931 cals

Unfortunately, many recreational swimmers are not actively engaged for the entire span of their workout. They may be in the pool for an hour, but they’re not actively moving for the better part of that hour. Rest periods and recovery laps must also be factored in to how many total calories are burned at the end of the workout.

The sad truth is that many swimmers exaggerate their intensity level and workout duration. Consequently, they deceive themselves into believing that it’s acceptable for them to devour an excess amount of calories after their swim because they “earned” it.

Despite raising physical activity levels, this overconsumption post-workout counteracts all the hard work that they did in the pool and leads to a caloric surplus.

A caloric surplus is a dietary situation where a person takes in more calories than what their body expends in energy during a fixed time interval.

To better explain how a swimmer can still be in a caloric surplus, I’ll use myself as an example.

Let’s say that I head to the pool and complete a freestyle swimming workout that lasts one hour. I weigh around 180 lbs, so I should have theoretically burned in the range of 572 calories to 817 calories according to the chart above.

After getting out of the pool, I feel a wave of exhaustion and slowly convince myself that I went above and beyond the workout norm, burning upwards of 1000 calories at the very least. In reality, I actually fragmented my workout with a series of rest periods and went at a slower pace than normal. Consequently, only a total of 600 calories were burned.

Once I get back home, I consume 1000 calories with the belief that I broke even for the day on my calorie count. This miscalculation of how many calories I burned negatively influenced my post-workout dieting mentality, which unintentionally culminated in a 400 calorie surplus for the day!

Under certain circumstances, miscalculations like these can leave an individual in a worst place than when they started, particularly if their primary goal is weight loss. This is why it’s so important to pay attention to personal dietary habits, as they can make or break your fitness aspirations.

Can Stimulate an Increase in Muscle Mass

Swimmers may also put on additional weight by packing on muscle mass. Although swimming is largely seen as a cardiovascular exercise rather than a muscle bulking exercise, it does still have the potential to stimulate muscular growth.

The reason that this is possible is that the muscle fibers can still tear in response to the resistance presented by the pool water. Once these muscle fibers are torn, the body repairs the damage by fusing the fibers together, making the muscles larger in both size and mass (source).

Swimming activates an assortment of major muscle groups in the body, including, but not limited to, the:

  • core abdominal muscles
  • shoulders
  • upper back
  • glutes
  • hamstrings

With such a diverse range of muscles being activated at once, there’s ample opportunity for muscle growth throughout the body. Over time, this muscle growth can compound, manifesting itself as a noticeable upward trend on the weight scale.

Generally, novice swimmers experience the highest rate of muscular growth, since their bodies are unaccustomed to the physical rigors of swimming (source). During these initial stages, their bodies are scrambling to adapt to this new training stimulus by packing on muscle as quickly as possible. In the bodybuilding world, this phenomenon has been loosely coined as “newbie gains.”

So if you’re completely new to swimming and see your weight escalating slightly, it may not be the worst thing to happen. After all, packing on additional pounds of lean muscle mass will may you look and feel stronger than you did before.

Do Most Swimmers Gain Weight or Lose Weight Over Time?

Now that we’ve established that it is possible to gain weight from swimming, you’re probably wondering what’s more common for swimmers to experience—weight gain or weight loss.

In the long run, regular swimming is more favorable toward weight loss, as it raises physical activity levels and forces the body to churn through more calories than it would otherwise. At the end of the day, the constant battle between weight gain versus weight loss comes down to how many calories you consume versus how many calories you burn.

A prime example of this can be seen with Olympic swimmer Michael Phelps. Phelps is one of the most decorated swimmers of all time, and for good reason. He devoted a minimum of five hours to swimming every day in the months leading up to his 2008 Beijing Olympic run.

To fuel this extremely taxing workout routine, Phelps would eat a whopping 12,000 calories per day (source). To put that into perspective, the recommended daily caloric intake for the average adult male is 2,500 calories!

Even with this monumental caloric intake, Phelps was able to retain his lean physique and stifle any unnecessary weight gain. He did this by keeping careful tabs on how many calories he consumed versus how many calories he burned.

The main takeaway here is that any form of physical exercise is supportive of weight loss, as it burns through energy and helps put the body in a caloric deficit.

The primary determining factor of weight loss versus weight gain, however, is an individual’s caloric intake. If you’re consuming more calories than your body is expending, you will gain weight over time, regardless of how hard or how often you swim. Even Michael Phelps would gain weight if he somehow managed to consume an extra thousand calories or two!

Rather than being skeptical about swimming regularly, you should shift that skepticism over to your dietary habits, as they’re likely the ones responsible for tipping the scales the wrong way.

How to Prevent Unwanted Weight Gain from Swimming

If all this talk of weight gain from swimming has you worried, fear not. There’s a multitude of ways to put a halt to any unwelcome weight gain before it becomes a serious problem.

Reduce Caloric Intake

As aforementioned, the very first thing you should address before anything else is your diet.

To ensure that you don’t pack on any more pounds, you need to make sure your caloric intake is at maintenance level or in a deficit by tracking your calories. Documenting your daily caloric intake may seem like a tedious task from an outside perspective, but it’s actually relatively easy to do if you use the right tools.

MyFitnessPal makes tracking your calories quick and easy, as the app keeps a food diary of all the things you’ve eaten throughout the day and provides a total daily caloric count. You can input meals and recipes onto the app, and even scan barcodes so you can save yourself the headache of manually entering the nutrition facts in yourself.

Tracking your calories will provides an accurate estimate of your daily caloric consumption and give you real tangible information to work with going forward. At the very least, this practice will make you more aware of what you’re putting into your body and encourage you to make better dietary choices to prevent weight gain.

As an added bonus, eating healthier foods also lends itself to better performance in the swimming pool!

Increase Swimming Frequency, Intensity, or Duration

Another way to prohibit a sudden increase in weight is to restructure your swimming workouts so that you maximize your calorie burning potential. Burning a couple hundred extra calories can be the difference between weight gain and weight loss.

You can improve upon your current swimming program by doing the following:

  • Increasing Frequency – Find the time to hit the pool once or twice more than you normally do. Generally, beginners tend to swim two to three times per week, whereas experienced swimmers tend to swim closer to four to five times per week. The more days you work out, the greater the opportunity to burn calories.
  • Escalating Intensity – Gradually increase your work capacity as you progress along your swimming journey. Tacking on more laps, swimming at a faster pace, and reducing rest periods are all viable methods of upping the intensity of your swim. This hard work ultimately translates into extra calories burned.
  • Extending the Workout – Slightly lengthen your workout whenever time permits to burn through those extra few calories. It may be tempting to cut your workout short, but doing so leaves calories on the table.

All of these strategies will require more physical exertion and mental discipline on your part, but it will be worth it in the end to stave off those extra pounds.

Incorporating Other Forms of Daily Exercise

If you have trouble changing your dietary habits or refining your swimming program, it would be a smart idea to explore other physical activities to build into your everyday routine.

These physical activities don’t have to be anything too drastic, like carrying logs around or chopping at tree stumps. It can be something as simple as walking to school instead of driving or playing basketball at the local park with some friends.

This should go without saying, but you should try to find physical activities that you have a genuine interest in. For myself, I’ve found that a daily morning walk helps me to get my day started right. Plus, I’ve always liked listening to podcasts and audiobooks while simultaneously keeping my weight in check.

If you’re curious as to how swimming stacks up to walking in terms of weight loss, click over to Swimming vs Walking: Which is the Better Exercise.

Although these exercise habits may seem trivial, they can have a significant effect if you do them on a regular basis. Often times, the margin between a caloric surplus and a caloric deficit is only several hundred calories. Making a concentrated effort to be more active does yield results if you go about it the right way.

The Bottom Line

Your body weight can increase from swimming if you overeat post-workout or pack on a high degree of muscle mass. Nonetheless, most swimmers tend to lose weight in the long run, since any form of physical activity supports a caloric deficit.

The good news is that any weight gain that comes with swimming can be largely reversed by consuming less calories, restructuring your swimming regimen, and integrating other forms of exercise into your day. In summary, you shouldn’t let your fears of weight gain stop you from swimming!

Sources: 1 2 3

Austin Carmody

I am the owner of HydroPursuit. I enjoy kicking back and getting out on the water as much as I can in my free time.

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