Do you lose weight running a marathon?

Running a marathon is a challenging feat that requires months of training and preparation. For many runners, weight loss is a common goal in marathon training. But does running 26.2 miles actually lead to significant weight loss?

Quick Answer: Yes, running a marathon can lead to weight loss, although the amount varies widely based on the individual. On average, marathon runners can expect to lose 2-10 pounds during marathon training. The calorie expenditure from running long distances creates a calorie deficit that results in weight loss over time. However, genetics, diet, and other lifestyle factors also play a key role.

Running a marathon requires a tremendous amount of training typically over the course of 4-6 months. During this training, runners gradually build up their weekly mileage which requires burning extra calories. The extra calorie expenditure coupled with following a healthy diet makes losing weight through marathon training completely achievable for most runners.

However, the amount of weight loss can vary quite a bit from runner to runner. Much depends on the individual’s baseline weight, genetics, diet, lifestyle factors, and how drastic the increase in mileage is during training. Running higher weekly mileages leads to greater calorie expenditure and an increased likelihood of weight loss. But the marathon itself only accounts for a small portion of total calories burned during training.

Overall, marathon runners can expect to lose 2-10 pounds on average during training. However, weight loss of 10+ pounds is also quite common in runners who significantly increase mileage and follow a healthy diet. Losing just a few pounds can still lead to big performance improvements. But weight loss is not guaranteed and should not be the only goal when training for a marathon. Finishing the 26.2 mile distance should remain the priority.

Calories Burned Running a Marathon

The number of calories burned running a marathon can vary substantially based on the individual runner. However, on average, most runners burn about 2,500 – 2,800 calories completing a marathon.

This large calorie expenditure in a single activity creates a significant calorie deficit, provided the runner does not drastically increase calorie intake on marathon day.

Here are some general estimates for calories burned running a marathon based on runner weight:

Runner Weight Calories Burned
120 lbs ~2,300 calories
150 lbs ~2,800 calories
180 lbs ~3,300 calories

As you can see, the more a runner weighs, the more calories they can expect to burn completing 26.2 miles due to having to carry more weight over the full distance.

Burning 2,500-2,800 calories is a significant calorie expenditure. For perspective, that’s about the number of calories sedentary adults should consume daily for weight maintenance. So running a marathon creates a large calorie deficit for most runners.

If runners do not increase calorie intake to match this large expenditure, they are likely to lose weight not just during the marathon but in the days following as the body recovers. However, the marathon itself only accounts for a small portion of total calories burned in training.

Calories Burned During Marathon Training

While the marathon burns a large number of calories itself, the bulk of calories expended actually comes from the months of high mileage training required.

Weekly training mileage can range from 10 miles per week for a beginner to over 60 miles per week for more advanced runners. Typically, runners will complete between 300-500 miles total over a 4-6 month marathon training cycle.

The calories burned per mile varies based on the individual’s weight. As a rough estimate, the average runner burns about 100 calories per mile run.

So for a runner averaging 30 miles per week for 18 weeks (540 total miles), they would burn around 54,000 calories from just the running portion of training alone. This is equivalent to over 15 pounds of body fat.

However, calorie expenditure is higher the more a person weighs due to having to carry more weight over each mile. Here is a table estimating calories burned per marathon training cycle based on weekly mileage and runner weight:

Calories Burned at 20 miles/week Calories Burned at 40 miles/week
120 lb runner 30,000 60,000
150 lb runner 37,500 75,000
180 lb runner 45,000 90,000

As shown, the total calorie expenditure from running spikes significantly as weekly mileage increases. Runners training at higher volumes can expect to burn a lot more calories, even if running pace is relatively slow. This leads to greater likelihood of weight loss.

But keep in mind, these are estimates only looking at calories burned from running itself. The calorie deficit ends up even higher when accounting for additional energy burned during cross-training, strength workouts, and general daily activity.

Factors That Influence Weight Loss

While creating a large calorie deficit through marathon training generally results in weight loss for most runners, the actual amount of weight lost can vary quite a bit.

Here are some key factors that influence the magnitude of weight loss:

Baseline Weight

Runners starting marathon training at a higher weight tend to lose more weight than lighter runners. Heavier individuals burn more calories per mile while running due to having to carry more weight. They also have a higher energy expenditure during day-to-day activities. So building up mileage creates a larger calorie deficit compared to runners starting at a lower weight.

Increase in Mileage

The more a runner increases their weekly training mileage, the greater the calorie expenditure and likelihood of weight loss. Runners going from 20 miles per week to 40 miles per week are likely to experience more weight loss than runners going from 40 to 50 miles per week for example. The body adapts to regular endurance training by becoming more efficient over time. So new runners generally burn more calories at a given pace.

Diet Quality

Diet accounts for a significant portion of a runner’s calorie expenditure outside of running itself. Runners who closely monitor calorie intake and eat a nutritious, low-calorie diet can maximize weight loss from marathon training. Avoiding excess calories from high-calorie junk foods and sugary beverages enhances weight loss.


Some runners simply have an easier time losing weight due to genetic factors that increase resting metabolism or make the body more susceptible to calorie restriction. Individual baseline hormones, muscle fiber composition, and other genetic variables can influence weight loss.


Getting adequate sleep helps maintain hormone levels and decreases appetite. Runners who regularly get 7-9 hours of sleep each night are less likely to overeat and generally find it easier to lose or maintain weight compared to those with poor sleep habits.

Strength Training

Runners who add regular strength training and cross-training build more metabolically active muscle mass. This leads to greater daily energy expenditure and an enhanced ability to burn fat through activities other than running itself. Combining running with other workouts maximizes weight loss.

Environmental Factors

Things like high work stress, financial or relationship concerns, and travel can all negatively impact diet quality and disrupt running routines. Managing life stress and maintaining a structured schedule ensures runners get in training and don’t overeat in response to external factors.

So while running higher mileage burns lots of calories, several lifestyle and genetic factors also influence just how much weight an individual loses during marathon training. Certain runners are simply predisposed to drop pounds more easily.

Average Weight Loss for Marathon Runners

Most marathon runners lose some level of weight while training for 26.2 miles. But just how much weight do runners lose on average?

Here is an overview of typical weight loss numbers reported from runners training for a marathon:

  • 2-5 pounds: This tends to be on the lower end but common for experienced marathoners or those with less weight to lose.
  • 5-10 pounds: This is the average weight loss for most first time marathon runners following a structured training plan.
  • 10-15 pounds: Runners can expect weight loss in this range when significantly increasing weekly mileage and closely monitoring nutrition.
  • 15-20+ pounds: Runners starting at a high weight and making drastic nutrition changes can sometimes lose 20+ pounds during marathon training.

These ranges are just averages and norms reported across thousands of marathon runners. Significant individual variability exists based on all the factors discussed earlier.

A beginner runner starting marathon training for the first time is likely to experience more weight loss compared to a veteran marathoner who maintains consistent mileage from year to year. Genetics also predispose some individuals to lose or gain weight more easily.

But in general, for a runner averaging 30-40 miles per week during 4-5 months of training, about 5-10 pounds of weight loss is quite reasonable. Losing just 2-3% body weight can make a big difference in performance for most runners without compromising health or nutrition.

Tips to Maximize Weight Loss

Here are some tips to maximize healthy weight loss during marathon training:

Slowly Build Mileage

Gradually increasing weekly mileage over several months creates the energy deficit needed for weight loss. This allows the body to adapt to prevent injury or burnout. Focus on consistency over speed work when aiming to lose weight.

Incorporate Cross-Training

Add cross-training like swimming, cycling, or yoga on 1-2 days per week. This creates an additional calorie deficit and builds fitness while giving running muscles a rest.

Add Strength Training

Aim for 2-3 strength training sessions per week in addition to running. Strength training is vital for building lean muscle mass and raising daily calorie burn. Compound exercises like squats and deadlifts are most effective.

Eat in a Calorie Deficit

To maximize weight loss, aim for a daily calorie deficit of about 500 calories through diet and exercise. Track intake using an app and focus on nutritious, protein-rich foods to feel satiated eating less.

Minimize Empty Calories

Limit liquid calories, sweets, fried foods, and other empty calorie sources. Focus on whole foods like lean proteins, fruits, veggies, and whole grains to get nutrients needed to fuel running.

Stay Properly Hydrated

Drink about 0.5-1.0 ounces of water per pound bodyweight daily. Carry water on all runs over 60 minutes. Hydration supports weight loss by controlling appetite and maintaining training intensity.

Get Plenty of Sleep

Aim for at least 7-8 hours per night. Lack of sleep alters hunger hormones and decreases energy for training. Prioritize sleep to support weight loss.

Following these tips maximizes the calorie deficit needed for weight loss while maintaining the energy and nutrition needed to sustain marathon training. Patience and consistency remains key – unrealistic weight loss goals are counterproductive.

Maintaining a Healthy Weight After the Marathon

Many runners work so hard to lose those 10 extra pounds through marathon training only to gain them all back shortly after crossing the finish line.

Here are some tips to maintain your hard-earned weight loss after the big race:

  • Gradually reduce mileage by no more than 10-20% per week – cutting back too quickly slows metabolism.
  • Take 2-3 weeks entirely off from structured running to allow the body to recover.
  • Transition into a maintenance running program of 15-30 miles per week.
  • Continue strength training and crosstraining 3-4 days per week.
  • Closely monitor diet and keep up nutrition habits formed during marathon training.
  • Accept a small amount of weight gain (2-5 lbs) to be expected after completing your goal marathon.

The most important factor is continuing regular exercise while not overdoing high mileage training weeks. Completely stopping exercise after the marathon signals to your body to conserve energy and store fat.

Additionally, keeping up the healthy diet habits formed while marathon training goes a long way. Avoid going back to old patterns of indulging in sweets, junk food, and liquid calories.

By gradually easing down training, maintaining fitness with crosstraining, and sticking with a healthy nutrition plan, you can keep off the weight you worked so hard to lose during all those months of marathon training.

The Importance of Body Composition

When your marathon training goals include weight loss, the number on the scale does not tell the whole story. The real goal is losing body fat while maintaining precious lean muscle mass as much as possible.

Runners who lose 5-8 pounds of fat while gaining 2-3 pounds of muscle can actually decrease body fat percentage and look leaner, while the scale itself might only show a 2-3 pound drop.

Methods like skinfold testing, DXA scans, and hydrostatic weighing can give insights into changes in body fat percentage versus total weight. But even simply taking waist measurements and how your clothes fit can indicate improvements in body comp.

Do not become discouraged if the scale does not move as fast as you like during training. If your clothes fit better and you look leaner in the mirror, you are likely still losing body fat. Some weight gain might just come from increased muscle mass.

Focus on performance improvements and body composition rather than just the number on the scale. Gaining muscle and losing fat is optimal, even if total weight remains stable. Improved race times indicate you are headed in the right fitness direction.

Potential Downsides of Weight Loss

While dropping extra pounds through marathon training is completely achievable and worthwhile for many runners, the desire to lose weight should not become unhealthy. Here are some potential downsides to be aware of:

  • May harmfully restrict calories and macros if taken to extremes
  • Can negatively impact female hormone levels and menstrual cycles
  • Increases risk of overtraining, injury, and burnout
  • Causes loss of lean muscle mass in addition to fat
  • Leads to mood issues, poor body image, or disordered eating

Runners must ensure they fuel properly for their training levels and maintain adequate calorie intake. Aggressively restricting calories can backfire by decreasing training capacity. A moderate calorie deficit combined with proper nutrition prevents the issues above.

Additionally, losing too much weight can create other problems. Minimally, runners may lose power and strength. In females, extreme weight loss can disrupt menstrual cycles and bone health.

Maintaining a healthy mindset around food while losing weight in a sustainable way keeps training and health optimized. Patience brings the best results.


Running a marathon requires tremendous effort and training over the course of many months. This increased training volume coupled with dialing in nutrition habits leads to weight and body fat loss for many runners.

While the actual amount of weight lost over marathon training varies quite a bit, on average runners can expect to lose around 5-10 pounds if coming from an untrained background. More modest losses of 2-5 pounds are common among veteran marathoners.

Maximizing mileage, adding cross-training, strength workouts, proper hydration and diet all help create the calorie deficit needed to optimize weight loss. Results also depend heavily on genetics, baseline weight, and other environmental factors.

Runners must strike a careful balance between achieving weight goals and fueling properly for their training. But moderate weight loss Achieved through consistent, patient work typically translates to improved marathon performance.

After crossing the finish line, runners should gradually reduce mileage while maintaining other fitness habits. Sticking with a healthy nutrition plan keeps the weight off long after completing 26.2 miles.

While the marathon itself burns 2,500+ calories, the real fat loss occurs through months of training in a consistent calorie deficit. Running a marathon provides an opportunity to transform your body composition for the better and establish lifelong diet and fitness habits.

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