Gaining Weight From Running? Here are 4 Reasons Why You Could Be Running But Not Losing Weight

Don't let the scale get you down.

Many beginners initially start running as a way to lose weight.

Indeed, among the many physical and mental health benefits of running, a running workout routine can burn calories, reduce body fat, and help you reach your weight loss goals or maintain a healthy weight.

However, some runners find that they are running but not losing weight, or worse, that they are running and gaining weight. Frustrating!

Let’s look at why this can happen and what to do about it.

a person running up stairs

Why Am I Not Losing Weight from Running?

1. You Might Be Overcompensating by Eating Too Much

You’ve probably heard the phrase, “abs are made in the kitchen,” which means that exercise and diet go hand in hand when it comes to slimming down or toning up.  

This does NOT mean you have to adopt one of the latest fad diets. What it does mean, is that losing weight requires a caloric deficit. 

This means you need to eat fewer calories than you are burning (calorie intake < calories burned).

If you’re gaining weight from running, it might be because you’ve started taking in extra calories to fuel your run but are overdoing it.

Running is usually a great way to make that happen because you can burn calories through sprinting or long-distance running. 

But on the other hand…you need enough calories to fuel your workouts and support overall health and wellness, and marathon training or high intensity interval training workouts can make you really hungry!

If you’re overcompensating due to an increase in your appetite, you will gain weight despite running.

Experiment with different sources of fuel and nutrition regimes: I am a proponent of consuming a snack that’s predominantly carbs an hour or two before your run. Carbs ensure your glycogen stores are topped off.

Also, stick to natural food and fuel sources. Energy bars might seem like a quick solution, but they’re often loaded with calories, sugar, and processed ingredients that your body struggles with.

2. You’re Gaining Muscle

A lady running on a trail with mountains and clouds in the background

When you ask, Can you gain weight from running? the answer is yes. But that’s not always a bad thing.

If you’re doing a lot of HIIT-style running workouts like hill running, or additional weight training, you will be building muscle mass.

If you gain muscle tissue and lose fat at the same time, your weight may not change, but your body composition will.

The best way to know the difference is the way your body looks and feels – if it’s firmer and more toned, you’re likely gaining muscle. If your pants are getting tighter or refusing to button, that is most likely from either gaining fat or water retention.

That’s why the metric for your ideal body should never be based on the number on your scale.

Ultimately, the best test to tell if running is ‘working’ is how you feel. 

If you’re getting healthy results, you will feel more energetic and strong, and will most likely have a more positive mood. 

If you’re gaining fat instead of muscle, you’re more likely to feel sluggish, groggy, and have symptoms of depression. 

When it comes to gaining weight from running due to building muscle, that’s a good thing! Keep doing what you’re doing – your body is getting healthier and stronger.

Man running in an urban environment wearing a tracksuit and headphones

3. You Might Be Experiencing Swelling After A Hard Workout

When you start any exercise program (but especially if you’re training for a long-distance race!), it’s perfectly normal for your body to go through some changes.

When physical activity stresses your muscle fibers, it causes micro-tears, which can then cause inflammation.

The body immediately works on healing those microtears (part of the muscle-strengthening process).

To do that, it sends excess water to the area to help the healing process, which can then show up as water weight gain1I Just Started Exercising — Why Am I Gaining Weight? (2020, March 9). Health Essentials from Cleveland Clinic. https://health.clevelandclinic.org/just-started-exercising-gaining-weight/ after running.

This is one situation where running does make you gain weight, but not in an unhealthy way.

If you’ve just started running and gained weight, or if you find yourself gaining weight from running every day or suddenly increasing your running intensity, then water weight gain may be the cause of your weight gain as your muscles adjust to an increase in intensity.

Your hydration efforts coupled with all the cardio you are doing are simply a natural part of the body’s recovery process.

In this case, all you need to do is make sure you’re eating properly, giving your body adequate time to recover in between runs, and go ahead and stick with your plan.

Man in nature in running gear with hands on knees

4. PCOS Could Be Causing Your Weight Gain – Not Running

Polycystic Ovarian Syndrome (PCOS) is a condition that affects 6% to 12% of women.2CDC. (2020, March 24). PCOS (Polycystic Ovary Syndrome) and Diabetes. Centers for Disease Control and Prevention.

It affects hormonal balance.

Many women with PCOS become overweight3Can Polycystic Ovary Syndrome Make You Gain Weight? (2020, February 20). Cleveland Clinic. https://health.clevelandclinic.org/can-polycystic-ovary-syndrome-make-gain-weight/ because of insulin resistance, which is a common side effect of PCOS.

Insulin resistance means your body produces insulin but can’t use it properly.

It’s normal to turn to running as an obvious solution to losing that excess weight, then find yourself frustrated because you’re still gaining weight, even though you’re sticking to the training plan and healthy diet and not overeating.

If you do have PCOS, you may be thinking that running is causing the weight gain; in fact, it’s likely just a symptom of the underly disease.

Dr. Kimberly Gecsi, OBGYN at UH MacDonald Women’s Hospital in Cleveland, Ohio, told Outside Magazine that running is still a great way to treat symptoms of PCOS (including weight gain).

You just have to follow a different diet that is than the diet for other runners.

Instead of fueling your running with carbohydrates, focus on lean proteins and healthy fats (like nuts, avocados, and fish) instead. That, combined with possible hormonal supplements like contraceptives, can help you lose that extra weight.

If you have PCOS, consider working with a registered dietitian to develop a healthy diet plan for weight loss while running.

a lady in running gear with her hands on her hips in a canyon

Related: Ideal Body Weight Range Calculator

Healthy Ways to Drop Pounds from Running

We’ve mentioned that the calorie deficit is an important aspect of losing weight. But here’s what that does NOT mean: It doesn’t mean you need to eat less than you feel you need or deny your body the chance to eat when you feel hungry. 

The effects of starving yourself for a calorie deficit are serious and are especially dangerous for distance runners, especially those training for longer distances like half marathons and marathons because your body needs calories to fuel workouts and recovery. 

If you don’t get the nutrition you need to fuel your run, you can end up getting dizzy or even passing out during your run. 

Your muscles will not develop properly, since they need healthy levels of carbohydrates and fats to use for energy. When you push yourself past those healthy limits, you end up with lifelong injuries. 

Here are two ways you can still generate a calorie deficit – and lose weight – from running. 

1. Build muscle

a lady punching the air next to a lake

Many runners will jump right into a training plan and run medium to long distances 5-6 times a week.

This is not necessary for accomplishing your distance and speed goals; it’s also not necessary for weight loss. 

The best way to run farther, faster, and lose weight, is by incorporating strength training into your running routine. When you build muscle, you burn more calories and body fat, which in turn tones your body and makes you look more ‘fit.’ 

As I mentioned above, building muscle can make you gain weight, but focusing on the number on the scale should never be the most important metric.  

Whether you want to lose weight to get healthier or to look a certain way, you’ll accomplish both by building some muscle, too. 

See our weightlifting guide for runners – it’s our recommended approach for strength training effectively.

a man wearing sunglasses in the race starting position on a road in nature

2. Eat as much as you need…but eat better. 

Keep in mind that the reason you’re hungrier as a runner is that your body is asking you for more fuel.

When you think of food as fuel for running, you’ll probably make some different food choices. 

What do we mean by fuel? It’s the different resources the body uses to create the energy you need for running. 

You probably already know that you should eat more vegetables, cut back on sugar and processed foods, and eat lean protein if you want to lose weight. 

But the important thing to remember about eating for fuel/weight loss is the quality of your calories over the number. 

a plate of sweet potato fries and greens

Eating 2000 calories of nutritious foods your body can absorb for your next run is much more effective for weight loss than consuming the same amount of empty calories that won’t support your workouts or your overall health.

Here are a few healthy food swaps: 

  1. Brown rice: Swapping out white rice for brown is just a small tweak in your diet, but will give your body more complex carbohydrates from the get-go. (If you’re on the fence about the importance of complex carbohydrates, read this article.)
  1. Salmon: This is not only one of the best sources of protein for runners, but it’s also full of omega-3 fatty acids, which support heart health, decrease inflammation, and speed up your metabolism. 
  1. Sweet potatoes: Swapping a white potato with a sweet potato will give you more nutrients. Sweet potatoes are full of vitamin A, vitamin C, beta-carotene, and manganese. These nutrients support your immune system and vision, prevent respiratory infections, and help regulate healthy blood sugar levels. 
a woman running on a trail next to the sea

Finally, there’s one thing you need to remember when it comes to gaining weight from running vs losing weight when running:

If you approach the process from a “quitting” perspective (for example: I need to quit eating sugar, or quit eating steak…etc.), you’re bound to slip up..and then give up. 

But when you approach the process from the perspective of replacing one thing for something healthier, you’ll see far better results. Instead of, I need to quit eating french fries, try, I’ll eat baked sweet potato fries and season them with something delicious. 

This puts your state of mind in a more positive frame, so that even when you do slip up (you’re only human, after all), you’ll be much more likely to get back up and continue the next day.

That’s what will ultimately help you stop gaining weight from running – and help you enjoy healthy food rather than dreading it!

Need some inspiration for healthy foods as you prepare for race day? You can read more about the best fuel for runners here.

A lady running on concrete, overlaid with text saying 'gaining weight from running? Here's why you aren't losing weight'


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Mia Kercher is a hiker, cyclist, and runner. After finishing her first marathon in 2013, she continued the sport but found a new passion in trail running. She now explores the glorious mountains in Portland, Oregon.

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