Does Body Weight Change How You Should Fuel During Exercise?

In episode 115 of The Eat for Endurance Podcast, Sports Dietitian Stevie Lyn Smith, MS RD CSSD returns to the podcast for part two of our series on performance fueling.

Last time, we tackled speed and intensity; today, we're diving into how body weight may change your fueling needs during exercise.

Whether you're training for a half marathon, Ironman, ultramarathon, or whatever else, understanding your body’s needs is essential for performance, recovery, and long-term health.

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Body Weight Doesn't Always Predict Your Pace

Athletes of all shapes and sizes have unique fueling needs based on their total body mass, as well as other factors like exercise intensity, duration, and sport.

It's true that body weight, as well as composition, can influence performance, especially in sports like running and cycling. However, being in a larger body doesn't necessarily mean being a slower athlete, just as being in a smaller body doesn't necessarily mean being a faster athlete.

There are MANY factors that can impact performance. That is why Stevie and I intentionally separated exercise intensity/speed and body size into two fueling discussions.

Also, please note that "larger" and "smaller" are relative terms. We don't define them in this episode on purpose.

A Quick Recap: Traditional Carb Recommendations

Historically, carb goals during exercise were based on duration (how long you're exercising) and intensity (how hard you're working).

Traditional carb guidelines suggest that you should fuel with:

• 30-60 grams/hour for 1-2.5 hour sessions

• Up to 90 grams/hour for >2.5-3 hour sessions

Body weight was not factored in, but the amount of glucose and fructose that our body could absorb per hour was. These simple sugars use different transporters when being absorbed in the gut, and athletes are able to reach higher intakes by consuming both together (often in a 2:1 glucose to fructose ratio).

More recently, research has shown that endurance athletes (including runners) may tolerate and benefit from 120g+ carbs per hour! Still, this is not body weight based.

Here's What Newer Research Suggests

A 2024 study in cyclists suggests that larger-bodied athletes may need more carbohydrates during exercise than smaller athletes to optimize performance.

Key findings of this study:

• Larger athletes oxidized significantly more ingested carbohydrates than smaller athletes

• Researchers suggested a target of 0.7 grams of carbs per kilogram of body weight per hour for better fueling, rather than sticking to 30-90+ g/hour

It's important to note the following:

• This was a very small study (only 15 cyclists)

• "Large" body mass was arbitrarily defined as >70kg or 154 pounds, which is not actually very large at all

More research is needed before changing carb guidelines during exercise, but it's a great reminder to stay curious and experiment with your fueling!

What This Means for You

Here are some key things to consider when creating your own fueling plan:

• Higher body weight = potentially higher carb needs

  • If you have more total body mass, you might benefit from pushing your carb intake closer to the higher end (or even above) traditional ranges

• Less body mass ≠ less fueling

  • Smaller-bodied athletes still need to meet carb needs based on effort, duration, and goals

• Training Status Matters

  • Newer or less-trained athletes may rely even more on carbs during workouts compared to seasoned endurance athletes

• Use your body’s feedback

  • Monitor your energy levels, recovery, GI tolerance, and overall performance to adjust your fueling

Beyond Carbs: What About Calories, Protein, and Fat?

For ultra-endurance athletes (long-course triathletes, ultrarunners, cyclists), you’ll also need to think beyond carbs:

• Calories: Generic advice like "250 calories/hour" might not be enough for larger athletes. You may need more total calories per hour based on your body size and effort, because you are burning more calories.

• Protein: Adding 5–10 grams of protein per hour during very long events (>2 hours) can support your muscles.

• Fat: Small amounts of fat may be helpful during ultra-distance events at lower intensities, but tolerance varies widely.

Pro Tip: As exercise duration increases, it becomes even more critical to meet energy demands, especially for athletes with higher weights.

Special Note on Weight Loss Goals and Fueling

It’s worth emphasizing that regardless of your body size or weight goals, you deserve and need to fuel your training.

Trying to restrict fuel during training to lose weight can lead to:

• Poor performance

• Increased injury risk

• Longer recovery times

• Potential health issues like REDS (Relative Energy Deficiency in Sport)

Fueling adequately is not a luxury! It’s a necessity for every athlete, in every body.

Conclusion: Body Weight May Change Fueling Goals

• Body weight may change how much you need to fuel during exercise, but more research is needed to explore this further

• Larger athletes may benefit from experimenting with higher carb and calorie intake during long sessions

• Smaller athletes still need adequate fuel

• Listen to your body and stay curious — experiment and adjust as needed

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Ready to Personalize Your Fueling Strategy?

If you're not sure how to create a personalized fueling plan, or you're tired of second-guessing what, when, and how much to eat, come join the Eat for Endurance community.

I've been supporting athletes with their everyday and performance nutrition for over ten years, and have a wide variety of services available to fit every budget.

• Join my membership service, Fuel for Life Crew, for $30/month (cancel anytime)

• Check out my free nutrition downloads

• Fill out a new client inquiry form if you’re interested in 1:1 nutrition coaching

Let’s take the guesswork out of fueling and help you feel strong, confident, and supported in every workout.

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Disclaimer – all information provided is for educational and entertainment purposes only and is in no way meant to replace individual medical and nutrition recommendations