by Cassie Bjork in Training Tips, image by Michael Hansen

Why am I gaining weight during marathon training?

Interested in writing for Get started now!

This is one of the most frequent questions that sports nutritionists and dietitians are asked by avid runners and marathon trainees. Weight loss is a common reason why many choose to train for a big running event, such as a marathon. So, when the miles you run increase and the pounds don’t proportionately decrease, (or worse, —the pounds go up along with the mileage,) it’s no wonder people get frustrated.

So what causes this weight gain? Is there a way to prevent it?


 All too often, athletes will eat more after a workout than they need, or think that because they are clocking in high mileage they can eat whatever they want. While running does increase your nutritional needs (especially for carbohydrates, fluid and electrolytes,) running is not a free pass to the buffet. The basic concept remains: Calories in must equal calories out to maintain weight (and more calories out than in for weight loss.) So pay attention to what you are consuming and how much you are actually burning. You don’t need to keep a detailed log of calories in and out, but when refueling after a run, do consider that each mile burns around 80-100 calories.

Drinking too many calories

When training for a marathon, sugary drinks don’t need to be consumed every day. It’s important to replace the electrolytes lost in your long runs, but you only need to consume sports drinks when a) exerting over an hour of exercise or b) exercising in extreme heat.  Overdoing it will cause your body to store the excess glucose, in turn causing the number on the scale to increase.


Carbohydrates are the most important nutrient for runners, as they are the body’s most efficient, ready-to-use form of fuel. Nevertheless, you may be taking in more than you need. If carbohydrates aren’t immediately burned after being consumed, they are stored in the form of glycogen for later use. Your body requires water to break down the glycogen for energy, so when you store carbohydrates, you also store extra water, which shows up on the scale.

All in all, you can see that there are many reasons why your weight may fluctuate during marathon training. Although it is completely normal, there are some ways to have control over your weight status during training and these will also contribute to better performance in your next run.

  • Eat regular meals and snacks throughout the day. Whether you’ve noticed a few extra pounds or are afraid of their possibility, now is not the time to skimp on caloric intake. Skipping meals or snacks will not benefit you in any way and could, in fact, harm you by slowing down your metabolism. When marathon training, you need energy from good nutrition more than ever. Aim to eat three balanced meals (with protein, fat and carbohydrate) along with two to three snacks— every single day.
  • Refuel and rehydrate within thirty minutes of finishing your run. It is important to replenish your muscles with carbohydrate, protein, fat and fluid very soon after a workout.  A great post-workout snack is a protein shake made by blending one cup of plain yogurt, one cup of fresh or frozen fruit, one fourth cup coconut milk and a scoop of protein powder. Another idea is a bowl of oatmeal with a couple spoonfuls of peanut butter and protein powder mixed in.  For a quick recovery drink, chocolate milk is a top choice by many seasoned runners. It has slightly higher sugar content than regular milk along with a nice balance of carbohydrate and protein, making for an easy, balanced choice.
  • Choose whole grains to avoid cravings. Especially if you are following a diet higher in carbohydrates, it is important to be selective of the types you are consuming. Carbs are in all sorts of foods— from pop and juice to whole wheat noodles and daily products. You may find that the more simple carbs you eat, the more you crave. Choose whole grains for an increased satiety factor (not to mention the many health benefits of fiber.)
  • Only consume beverages with benefits. Hydrate your body with water, water and more water. Aim to avoid “empty-calorie” beverages like juice, energy drinks, sweetened waters and soda. Chocolate milk is a good post-recovery drink but shouldn’t become a staple at meals. And again, limit sports drinks to only in the two circumstances previously mentioned (running duration greater than an hour and/or in extreme heat.)

Keep in mind that it is important to make healthy choices for your weight AND the affect it will have on your running performance!

Other posts