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Why You Might Be Gaining Weight Running And How to Fix It

Amanda Wendorff

If you're gaining weight running, you're not alone! While running may be the best form of exercise to lose weight, it doesn't work for everyone, and many people even gain weight while exercising at a high level. MOTTIV's Founder even gained 12 pounds in a year while training for two half-Ironman triathlons and one Ironman triathlon; we get how frustrating this can be!

In this article, we'll share the reasons some runners still gain weight running; you'll learn everything you need to know about running and weight gain. Whether you're a beginner runner or someone who has run for years, this article will help all runners who are trying to lose weight. We'll debunk some myths, provide scientific explanations, and offer practical solutions to help you align your running routine with your weight loss goals.

Key Takeaways You'll Learn From Reading This Article

  • Insight into how people can experience weight gain despite increased running
  • Factors that contribute to weight gain in runners and how to address them
  • Balancing calorie intake and expenditure (calories in vs calories out) for runners
  • The best strategies for runners to manage and lose weight
  • The importance of combining diet, exercise, strength training, and recovery
  • An overview of the role of muscle mass and metabolism in a runner's weight
  • Tips on optimizing your running routine and diet for better weight management
MOTTIV app user Kurt Lundqvist and his wife running a half marathon!

What Causes Weight Gain?

At its core, weight gain is about an imbalance in the energy equation - consuming more calories you burn. But this equation is often oversimplified and has layers of complexity, especially for runners. There are a number of factors that affect both calories in and calories out, and some additional factors that are completely unrelated to calories can cause weight gain.

Many regular body functions can make it hard to lose weight running. For instance, if you increase your running mileage significantly after you start running, your body might respond by increasing your appetite or slowing down your metabolism, making weight loss much more difficult. These natural body functions are just the most straightforward instances of challenges with running and weight loss.

Each runner's body responds differently to exercise. Factors like age, gender, genetics, health issues, and even past weight loss history can influence how our bodies react to increased physical activity. Understanding these nuances is important for runners to manage weight gain effectively.

6 Reasons a Runner Might Gain Weight

#1: You Might Be Over Eating

The 'run to eat' mentality can be a pitfall for many runners. After a grueling run, it's tempting to reward ourselves with food, often under the guise of 'refueling.' However, this can easily lead to overconsumption. Many of us overestimate the calories burned during a run and overcompensate by eating more - sometimes significantly more than what we've actually expended.

Additionally, when you underfuel before or after a run, you might find yourself incredibly hungry later, leading to impulsive eating choices and overconsumption. It's a delicate balance - eating enough to fuel your runs and aid recovery but not so much that it leads to a surplus in calories.

Many studies have looked at issues around exercise and disordered eating; it's very common and not entirely in your control. Despite what fitness influencers might say online, willpower to eat less isn't an easy solution because hunger hormones like leptin and ghrelin are more powerful than most people's willpower.

Suppose you find yourself snacking frequently, feeling hungry quite often in the evening, or feeling tired frequently despite getting more than 7 hours of sleep a night. In that case, it's a sign that you're not eating enough earlier in the day, particularly around when you workout.

If you want to know exactly how many calories you burn during your runs, enter your run details in the calculator below.

2. You're Gaining Muscle Mass

Initially, as a runner, especially if you incorporate resistance training, you might gain muscle mass. This is good for your overall health and long-term performance, but it can be misleading when you step on the scale because muscle is denser and weighs more than fat. What's happening in your body is a good thing; however, this can temporarily appear as weight gain.

In the long run, increased muscle mass is hugely beneficial. Muscle fibers burn calories at rest, while fat does not, boosting your overall metabolic rate. This means that, over time, you'll burn more calories, even when you're not running. The key is patience and understanding that this phase of weight gain is part of a healthier body composition transition.

Suppose you've taken up a new strength training routine to go along with your running; great! Keep doing what you're doing; just understand that you may gain weight before you start to lose it.

3. You Might Be Experiencing Inflammation and Water Weight Gain

Weight loss isn't always just about reducing body fat!

Exercise has been linked to reduced inflammation and water retention, even in people who have experienced long-term chronic inflammation. So, while running can lead to physical stress and acute inflammation in the days after a hard workout, it's unlikely that the exercise is causing the inflammation.

However, things like food sensitivities or other health issues can cause such high levels of chronic inflammation that weight loss is nearly impossible, and weight gain might actually occur. Our CEO, for example, has many food sensitivities and has gained and lost 15 pounds several times without any changes in his exercise routine.

If you find that you feel bloated, have skin problems, frequent diarrhea, heartburn, or generally feel frustrated with your lack of progress, there may be a food sensitivity or health issue causing you to gain weight running.

4. You May Have PCOS

For female runners, (Polycystic Ovary Syndrome or PCOS can be a hidden factor in weight gain. PCOS affects how the ovaries work and is associated with hormonal imbalances, including insulin resistance. This resistance can lead to the body storing more fat, especially around the abdomen, making weight loss a challenge.

Understanding and managing PCOS requires a holistic approach, often involving diet modifications, specific exercise routines, and sometimes medication. Women runners with PCOS might need to pay closer attention to their dietary choices and exercise patterns to manage their weight effectively.

5. Your Metabolism May Have Slowed Down

A common misconception is that more exercise always equates to a faster metabolism. However, suppose a runner engages in prolonged, intense running without adequate nutrition and recovery. In that case, the body may start to use muscle tissue for energy and slow down the rate of metabolism, both causing fewer calories to be burned every day.

This phenomenon is often seen in retired professional athletes. Their metabolism, which was once revved up by intense training, slows down in the absence of that training regimen. Consequently, they might gain weight post-retirement unless they adjust their calorie intake and maintain an active lifestyle.

Muscle is metabolically active tissue, so losing muscle can slow down your metabolism, making it easier to gain weight. Biggest Loser TV show contestants have been studied because most contestants gain huge amounts of weight after the show. Researchers found these individuals trained so hard and underfed themselves for so long that their metabolism slowed down to the point at which weight loss was impossible and weight gain was inevitable.

Large increases in exercise, combined with eating less, might lead to weight gain via a slower metabolism in just 6-9 months. This is why our training plans ramp up very gradually and feature mini-breaks.

6. You're Not Recovering Properly

Inadequate recovery can trigger an increase in cortisol, a stress hormone. Elevated cortisol levels over a prolonged period can interfere with weight loss and can even lead to weight gain.

This is why recovery is as crucial as the training itself. Ensuring adequate rest, including proper sleep and rest days, is essential to keep cortisol levels in check and support overall health and weight management.

5 Keys to Lose Weight From Running

#1. Strength Training

Strength training complements running by building muscle mass, which is key to maintaining a high metabolic rate. This doesn't mean you need to become a bodybuilder; incorporating basic weight training exercises a few times a week can significantly impact your body composition and calorie-burning capability.

In addition to burning calories, strength training helps prevent injuries by strengthening the muscles and joints used in running. A stronger body can handle the stresses of running better, allowing you to train more consistently, which is crucial for weight loss and overall fitness.

2. HIIT Training

High-Intensity Interval Training (HIIT) is a game-changer for those looking to enhance their weight loss through running. Research, including studies in the Journal of Obesity and the Journal of Diabetes Research, has shown that HIIT can lead to greater fat loss compared to steady-state cardio. The reason lies in HIIT's ability to continue burning calories long after the workout is finished, a phenomenon known as the 'afterburn effect.'

However, balance is key. HIIT is intense and can be taxing on the body, so it should be integrated thoughtfully into your training plan. One or two HIIT sessions per week, combined with more moderate running workouts, can optimize fat loss while preventing burnout and injury.

3. Easy Long Runs

While HIIT offers an efficient way to burn fat, it's not sustainable or advisable to do it every day. Here, easy long runs come into play. They're less intense but last longer, helping you burn a significant number of calories over an extended period. These runs are also great for building endurance, improving cardiovascular health, and giving you a mental break from the intensity of HIIT.

An ideal running plan for weight loss would include a mix of short, high-intensity sessions and longer, slower runs. This balance tipped primarily towards easy running, will keep your body systems healthy and avoid most of the issues listed above.

4. Burn More Calories Than You Consume

The cornerstone of weight loss is burning more calories than you consume. However, this doesn't mean you should drastically cut calories, as this can be counterproductive and lead to muscle loss and a slower metabolism. Instead, focus on creating a moderate calorie deficit that's sustainable in the long run.

Tracking your calorie intake can be incredibly helpful, and tools like the Senza app (available on Google Play) make this process easier. Remember, the quality of calories is as important as the quantity. Nutrient-rich foods will fuel your runs better and keep you satiated longer than empty calories from processed foods.

5. Eat an Optimized Runner's Diet

Your diet plays a crucial role in supporting your running and weight loss goals. A well-balanced diet ensures you have the energy for your runs and aids in recovery and muscle building. Here are some principles to guide your dietary choices:

  • Always eat before your runs to fuel your body.
  • Refuel within 30 minutes of your runs to aid recovery.
  • Avoid prolonged calorie deficits; they can lead to muscle loss and metabolic slowdown.
  • Hydrate adequately; dehydration can lead to increased hunger and overeating.
  • Focus on whole, unprocessed foods for nutrient density and satiety.
  • Aim for a protein intake of about one gram per pound of body weight for muscle repair and satiety.
  • Ensure your overall calorie intake is adequate; undereating can lead to overeating later.

FAQ for People Who Are Gaining Weight Running

Q: Why do runners gain weight?

A: Runners might gain weight because they overestimate the number of calories burned during a run and end up consuming more calories than they actually burn. Additionally, some new runners may experience increased hunger levels and end up eating more than necessary. Finally, there may be other health concerns related or unrelated to running that are causing weight gain.

Q: How can I prevent weight gain while distance running?

A: To prevent weight gain while distance running, it's important to pay attention to overall caloric intake and ensure that you're not consuming more calories than you're burning. Additionally, incorporating strength training and HIIT into your exercise routine can help maintain muscle mass and prevent excessive weight gain. Finally, overall health needs to be in good shape to allow for weight loss to occur.

Q: Is getting enough protein important for runners?

A: Yes, getting enough protein is essential for runners as it helps in muscle repair and growth. Adequate protein intake is the most satiating (filling) macronutrient, so it can also help control hunger and prevent overeating, which can contribute to weight gain.

Q: What should I eat to avoid feeling hungry after running?

A: As a rule of thumb we recommend consuming a balanced meal 30-60 minutes before every run, a small recovery meal in the 15-30 minutes after a run, and another full meal 60-90 minutes after a run.

Q: Is running a good way to lose weight?

A: Running is the most effective method of exercise for burning calories, which will set the foundation to lose weight through distance running. However, people need a balanced approach of a good diet, strength training, and a solid calorie balance in order to lead to weight loss

Q: How does not getting enough sleep affect weight when running?

A: Not getting enough sleep can affect weight when running as it may lead to increased levels of the hunger hormone ghrelin and decreased levels of the satiety hormone leptin, potentially leading to overeating and weight gain. Additionally, inadequate sleep can impact recovery and muscle repair, affecting overall physical performance.

Q: How can I make sure I'm not overeating after a run?

A: To avoid overeating after a run, make sure you eat before and shortly after every single run. Most of the calories you eat during a day should be eaten in the half of the day when you perform your workout.


Running can be a great way to lose weight, but it requires the right strategic approach and the avoidance of some major pitfalls. Understanding the reasons behind weight gain and implementing the keys to losing weight from running can lead to a healthier, more balanced approach to your fitness journey.

Remember, each runner's body is unique; the results of one person might not be possible by another. If you want to lose weight and running just isn't working for you, some of the ideas in this article may be the cause of your weight gain that you might not be considering. Knowing the reasons why you might be gaining weight is the first part of the process of fixing the underlying issue.

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Amanda Wendorff

| Author

Amanda Wendorff is a professional triathlete, focusing on the 70.3 and 140.6 Ironman distances. In the last several years she’s competed in multiple gravel bike races. Top Achievements: Top 3 Ironman Ireland and Ironman 70.3 Coquimbo, Multiple time top-5 finisher, 3rd Overall at Moran 166 Gravel Race in Michigan, Age group podium at Gravel Worlds, Big Sugar, and Ned Gravel in first year of gravel racing.

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