6 Reason You Look Fatter After Running

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6 reasons you look fatter after running

Most of the time, working out makes you feel good. When you finish a workout, your endorphins are pumping, sweat is dripping, and some of us find it tempting to check ourselves out in the mirror or snap a pic of our progress.

If you’ve been doing cardio or running, it’s likely that you actually look bloated, puffy, and fatter after your workout than you did before. It doesn’t result in the same flattering look that swollen muscles have after strength training.

So, why do you look fatter after running?

You look fatter after running because the heat from your temperature causes blood vessels to expand, especially in your stomach. Being overly hydrated or dehydrated, swelling from micro-tears, and having oxygen in your digestive tract also causes swelling. Finally, the foods you eat beforehand also affect how bloated you are after a run. 

Below, I’ll give you six answers regarding, “Why do I look fatter after running?” and talk about what you can do to help manage it. We’ll also go over how long you can expect it to last and what actually happens to your body during and after a run.

Why Do I Look Fatter After Running?

It can be discouraging to look in the mirror after a run and see a sweaty, bloated mess. While you could just avoid the mirror, it’s also helpful knowing why you might look bigger after a run and have the reassurance that the bloating will go away. Here are the reasons why.

Heat and Blood Vessel Expansion

One of the biggest reasons that people look fatter after running is because of heat. Whether you are doing cardio outside in the sun or in a warm environment, the increase in your body’s temperature makes your blood vessels open up and expand.

When blood vessels expand, it shifts the tissue in your body. In most cases, air gets trapped in the tissues between these vessels and that results in bloat. This is especially true for areas like your abdomen, where there is a lot of excess tissues. It’s also noticable in areas with thinner skin, like your face.

For this reason, the best way to manage it is ensuring your body doesn’t overheat. This is sometimes easier said than done depending on your workout routine. When it is especially hot outside, however, it might be better to opt for an air-conditioned cardio workout on an exercise bike or treadmill.

Wearing the right workout clothing also helps keep you cool. Opt for breathable clothing that will help you regulate your temperature better, especially if you are on the heavier side and sweat more than the average person.

Fluid Retention

The amount of water you drink before, during, and after you put on your running shoes plays a big role in how bloated you’ll be when you finish your workout. However, this isn’t as simple as avoiding too many fluids- staying hydrated is also critical to a healthy, productive workout and dehydration makes you look bloated, too.

When you’re dehydrated, your body struggles to regulate body temperature and you can become fatigued. Not having enough fluids also makes it harder to complete your workout and actually makes it more likely that your body is going to hold onto fluids instead of sweating them out.

According to the University of Utah, the best way to determine how much water you need to drink is to check your water weight. Weigh yourself before and after your workout to find out how much you are losing in pounds. Then, drink 24 ounces of water for every pound you’ve lost.

Of course, you should still drink a little water beforehand and during your workout, too. Over time, you’ll be able to get an average for how much water your body needs so you can plan accordingly.

Muscle Tears and Repairs

Any type of intense exercise is going to break down your muscles, whether you are lifting weights, doing calistenics like pull ups or push ups, or doing some type of cardio. If you have swelling in your legs after a run, it could just be a sign that you’ve been working the muscles in this area. In this case, that bloated appearance is a good thing.

Working out causes micro-tears in your muscles. When your body senses these tears, it sends fluids in the form of plasma to the area to start the healing process. These tears are normal and this is how muscle is built- by breaking down the muscles so that they grow back stronger.

These micro-tears are the reason that people taking post-workout selfies look so great showing off their muscle gains. When do cardio, however, this can result in more of a bloated appearance because of everything else that is going on.

Swallowing Too Much Air

One of the things associated with cardio is heavy breathing, especially when you are doing an intense workout. This heavy breathing makes it easy to swallow more air than you need. When this happens, instead of going into your lungs, this excess air travels through your digestive system.

Air in your digestive system gets trapped and stored until your body is able to release it, usually by burping or expelling it in other ways. Whether it’s in your stomach or another part of your digestive tract, this trapped air takes up room in your abdomen and results in bloating.

Eating Before a Workout

Cardio is a lot of work and eating something is important for ensuring you have enough energy to complete your run. That being said, what you eat and how soon you eat before your workout matters, too.

Keep in mind that digestion is a process. While your body does start breaking down food as soon as you start eating it, there is some time that passes while your body breaks everything down and converts it to energy.

While you are working out, your body is focused on providing energy for the task at hand. This means that you have freshly eaten food sitting in your belly, chances are the digestion process is going to come to a screeching halt once you start working out. The food in there can cause a bloated appearance, especially if your body retains water or air during your workout, too.

You should eat something, but make sure that you choose a food that is going to fuel you and be easy to digest. Additionally, eat at least 30 minutes to an hour before you workout. Here’s a Youtube video that talks a little about pre-workout food choices.


Edema is a term used to describe any type of swelling that happens in the body. When doing cardio, it’s most common for swelling to happen in the abdomen, the legs, ankles, and feet, and even your hands.

Edema caused by running happens when fluids pool in the legs or hands. Usually, this happens from the gravity pulling fluids down toward your feet and legs. However, it can also happen in the arms from the back-and-forth motion of your arms while running, especially if you don’t have them elevated above the heart.

In most people, the valves in their legs have the job of pushing blood in the area back up towards the heart. When this doesn’t happen, whether from exercising or having poor cardiovascular health, all the trapped blood and fluids in the tissues result in swelling.

If you have leg swelling that’s especially bad after running, try elevating your feet above your heart once you are done with your workout. Propping your legs up gives your body a little help pushing those fluids back up toward your heart.

How Long Does it Take for Bloating to Go Away After Running?

In most cases, bloating goes away within the first hour or two after running. For those situations where it doesn’t, symptoms will definitely disappear by the following day. They are temporary and you should never let those side effects dissuade you from the commitment you’ve made to your health by working out.

Some people also find that the more that they do cardio and stick to their workout routine, the easier it is for their body to adjust to what is happening during a workout. With any good workout routine, however, you generally increase the difficulty of your workout over time to help you reach your goals.

Am I Still Burning Calories if I Look Fatter After Cardio?

The good news is that regardless of how you look in the mirror after a workout, you are still burning calories during your run. Plus, you’re giving your body all kinds of other benefits including building lean muscle mass, increased blood flow, better sleep and mental health, reduced pain, and a decreased risk of diseases like diabetes, high blood pressure, heart disease, and stroke.

It’s important to remember that even if it seems like you’ve gained weight by appearance, this isn’t the truth. You actually need to increase caloric intake by a whole 3,500 calories to gain a single pound of fat.

Additionally, there’s a lot more to overall health than the number on the scale, particularly when you consider that muscle mass weighs differently than fat. There are also a number of other things that make your weight fluctuate, including water weight and food that hasn’t passed through your digestive system yet.

Is Cardio a Good Way to Lose Weight?

Yes, cardio is a good way to lose weight. However, it works best when you are doing more than just running as part of a workout regimen. Making smarter food choices is also going to help you reach your goals.

As with all things in life, balance is the best way to ensure you are getting the most out of your workout. Cardio is a great way to support your fitness regimen, but it’s also helpful to do at least light weight training to get the most out of your workout.

Additionally, switching things up is a great way to ensure your body doesn’t get too used to your workout routine. If your body adjust too much and it seems easy, then you aren’t getting the same benefits as you used to.

Final Word

Hopefully, this article has answered all your questions about “why do I look fatter after running?” Chances are, you look bigger because the heat from intense workouts like cardio causes blood vessels to expand. Being over-hydrated or dehydrated, swallowing too much air, eating before a workout, muscle repairs, and edema also all contribute to how big you look.

Fortunately, all of these things are something that dissipates within the first few hours after running. You also shouldn’t let them discourage you from working out. Even if you appear fatter, any type of cardio offers a lot of benefits to your overall health. Plus, this bloating won’t be as intense once you adjust to your workout.

Camila R.

Camila is a body positive blogger and fat activist that's focused on helping people of all sizes live life big! That means accepting yourself at any size and just enjoying life! She lives in New Mexico with her husband and two chihauhuas.

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