Weight Gains Before or After Marathons

Smiling runners drinking water after marathon

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Many new marathoners sign up for the race with hopes that the training will help them to get a leaner, fitter body. In some cases, the long miles and endless hours of running will result in weight loss. But in other cases, it results in weight gain. And to make matters worse, weight gain after a marathon can happen as well.

Common Causes of Marathon Weight Gain

Some published studies have shown that weight loss is more common than weight gain during and after training is complete. But weight gain does occur in some people. If you find that you are gaining weight during or after a marathon, you are not alone.

There are several key factors that can affect your weight during training. To keep your training on track and your weight healthy before and after a marathon, consider a few key factors. Depending on when weight gain occurs, there may be different causes of marathon weight gain.

Before a Marathon

During marathon training, your running mileage increases. However, your appetite is likely to increase as well. As a result, you may boost your food intake. While it is important to consume enough calories to fuel your runs, it can be easy to consume too many calories.

Many runners (understandably) feel entitled to an indulgent meal or regular desserts after pounding the pavement for hours. The problem is that you may end up consuming more calories than you burned during your runs. The increased calorie intake leads to weight gain.

One of the most commonly cited causes of marathon weight gain is increased food consumption. Often the foods chosen after hard workouts and long runs are high-fat, empty-calorie foods—foods that don't provide enough nutrients to fuel your training.

Another explanation is that during marathon training, your body is learning to store carbohydrates as fuel (glycogen) for your long runs. Those glycogen stores are important for completing long runs successfully. They will also help you to avoid "hitting the wall" on race day.

But your body requires additional water to break down and store glycogen. This extra water shows up as (temporary) extra weight on the scale.

Lastly, as you're training, you're building muscle mass. Muscle is denser than fat, so you may see an increase in your overall body weight.

So should you worry about weight gain before the marathon? What matters most is how weight gain affects your training or race outcome. One study showed that the most successful marathoners decreased their body weight by 3% to 4% during training. However, this study did not evaluate body composition (i.e. muscle mass or water weight).

While several factors can lead to pre-marathon weight gain, there are different types of weight gain. Weight gain from excess calorie consumption can—and in some cases should—be avoided. But you don't necessarily want to avoid weight gain from increased muscle mass or efficient glycogen stores.

After a Marathon

Post-marathon weight gain is more common than weight gain during training. Many marathoners get used to consuming more calories than normal to fuel their training runs. It can be tough to put the brakes on these eating habits once the marathon is over. And since you're not running as much as you were doing training, all those extra calories can quickly lead to weight gain.

Also, you may lose some muscle mass after the marathon if your training hours decrease substantially. A less muscular body requires less fuel, even at rest. So you need even fewer calories to sustain your metabolism.

While weight gain during training can be beneficial in some circumstances, weight gain after your marathon is probably not a good thing. Increased weight from the overconsumption of food (a calorie surplus) is likely to be stored as fat.

How to Prevent Marathon Weight Gain

There are different strategies for managing weight gain during and after marathon training. But the first step is to make sure that you are at a starting at a healthy weight.

A body mass index (BMI) calculator or a body fat percentage calculator can give you a general idea if your weight is healthy. Once you know that you are at a healthy weight, use a calorie calculator to make sure that you are consuming the right number of calories each day.

Body Mass Index (BMI) is a dated, biased measure that doesn’t account for several factors, such as body composition, ethnicity, race, gender, and age. 


Despite being a flawed measure, BMI is widely used today in the medical community because it is an inexpensive and quick method for analyzing potential health status and outcomes.

Once you know how many calories you should eat each day, start to log your food intake and make sure that there isn't a big gap between the two numbers. If you find that you are eating much more than you need to, evaluate your food habits and consider making these changes.

Before a Marathon

If you are concerned about weight gain during marathon training, use different methods to evaluate your body size. Invest in a body weight scale that can show not only overall weight, but also body fat percentage. Some scales even track water weight.

Your body fat scale may indicate that while your weight is increasing, your body fat is decreasing during training. This means that your body is putting on more muscle and losing fat. Increased muscle mass can help you to run more efficiently during the marathon.

You can also take note of how your clothes fit. If your weight is increasing but you notice that your clothes are getting looser or fitting the same, it is likely that your body composition is changing for the better.

Reduce Calories Consumed in Beverages

Sports drinks can be high in calories. Make sure that you aren't consuming them on shorter runs when water will suffice. And consider reducing your intake of other high-calorie beverages, such as alcohol and caffeinated sodas. Not only do these drinks add calories, but drinking them can lead to dehydration, which can cause fatigue during runs.

Focus on Fiber and Protein

Build meals around lean sources of protein (such as chicken breast, legumes, and seafood) and fiber-rich carbohydrates (such as green leafy vegetables, whole grains, and fruit). Protein helps you to build and repair muscle tissue after workouts. And both fiber and protein help you to feel full after eating. This will help you to combat hunger cravings that can happen when you train more often.

Choose Fats Wisely

During training, you might be able to consume slightly more fat than you would typically. But that doesn't mean that you should eat any fat in any quantity. Avoid fried foods and saturated fat.

Stick to sources of poly- and monounsaturated fat, such as nuts, seeds, plant-based oils, and avocado. Consume these fats in moderation, because even though they provide heart-healthy benefits, they still contain nine calories per gram.

Plan Ahead

Marathon training takes a lot of time. Many runners find themselves running from home to work to training without enough time to stop and eat a full meal. It's smart to carry a few snacks with you so that you are not stuck buying food from a vending machine or fast food restaurant.

Focus on Performance

Keep in mind that in order to reach your marathon goals—whether it is simply to finish the race or set a PR—your body will change during training. Your legs may get bigger as you build strong muscles in your quads and hamstrings.

These changes may come with an increase in the number on the scale, but they also come with a stronger, faster, more efficient body. And that's a good thing!

Try to focus on performance goals: completing workouts consistently, increasing endurance, getting faster, and boosting your mental strength. These are lifelong skills that will stay with you and help you to maintain a healthy, fit life even after the marathon is over.

Postpone Weight Loss Goals

While you might lose weight naturally during training, trying too hard to restrict calories when your mileage is increasing can cause fatigue, frustration, and lack of motivation. It is nearly impossible to complete a long run if your body is lacking calories and especially carbohydrates.

If your ultimate goal is weight loss, focus on food quality rather than on food quantity. Eating healthy meals and skipping empty-calorie foods may help you to reach your weight loss goal. If not, wait until after the marathon is over to attempt a dedicated weight-loss program.

After a Marathon

If you're worried about gaining weight in the months after completing a marathon, take a proactive approach.

Keep Exercising

Some marathoners are so burned out mentally and physically from the marathon that they completely stop running and working out. Try not to wait too long after the marathon to get back to running.

Once you get out of your running habit, it's tough to get back into it. Even though you'll be recovering for a few weeks, you can still do short, easy runs or cross training in the days following your marathon.

Pick Another Race

You don't have to plan to run another marathon, but having the date of another race on the calendar will motivate you to keep running. Look for races in your area and running groups that are training for upcoming races.

Celebrate in Moderation

After you've completed a marathon, it's tempting to overindulge while you're celebrating your achievement with family and friends. It's fine to celebrate your accomplishment with an indulgent meal and some drinks, but try not to let it turn into a month-long celebration. Also, keep portion control in mind.

Choose Healthy Rewards

You can also celebrate your accomplishment with something other than food and drink. Treat yourself to a much-needed post-marathon massage or buy yourself some new running gear. Getting some new running clothes will also keep you motivated to continue running.

Keep Healthy Snack Habits

Even though you may not be running as many miles each week, you may still find yourself feeling hungry all the time. Whether you're at work, home, school, or on the go, make sure you're always prepared with healthy snacks so you don't eat unhealthy, high-calorie convenience foods.

Track Food Intake

After the marathon, recalculate your caloric needs based on your reduced activity level. Then try to stay within the recommended numbers.

It's easy to consume too many calories when you're not really aware of how much you're eating and drinking. Once you start keeping track of your calories, you may be shocked at how many calories you're taking in, and you'll be able to identify areas for improvement.

Display Your Finish Line Photo

Whether it's on your desk, your refrigerator, or your wall, display your race photo proudly. Being reminded of your marathon completion will help motivate you to continue running, whether or not you ever do another marathon.

A Word From Verywell

Choosing to run a marathon is a big commitment. It takes substantial physical and mental energy—especially when you have other priorities in your life. Trying to lose weight at the same time is likely to be too much.

As you train, try to focus on staying healthy. Eat well, get enough rest, and follow a smart training plan to avoid injury and stay motivated. If your weight fluctuates slightly, don't worry about it unless it begins to affect your performance.

If weight gain continues to be problematic, consider investing in an appointment with a registered dietitian with expertise in running or sports performance. Together you can develop a meal plan that helps to keep your hunger at bay while keeping you properly fueled for your workouts.

1 Source
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Zouhal H, Groussard C, Minter G, et al. Inverse relationship between percentage body weight change and finishing time in 643 forty-two-kilometre marathon runners. Br J Sports Med. 2011;45(14):1101-1105. doi:10.1136/bjsm.2010.074641

Additional Reading

By Christine Luff, ACE-CPT
Christine Many Luff is a personal trainer, fitness nutrition specialist, and Road Runners Club of America Certified Coach.