How many calories do I need for running?

For distance runners, balancing energy intake is crucial—too little and you risk fatigue and injury; just right and you unlock peak performance. This guide will simplify how to determine and adjust your energy needs, maintain the right balance, and effectively monitor your intake for optimal running health. Let's gear up for a run where every step is fuelled with purpose.

How do I measure my calorie needs?

There are many ways to estimate calorie needs, each with pros and cons.

Doubly Labelled Water and Indirect Calorimetry
Doubly labelled water, the gold standard for real-life energy expenditure measurement, is often impractical due to high costs. In the lab, indirect calorimetry is preferred, measuring energy cost via oxygen and carbon dioxide analysis. However, its accuracy is limited to structured activities and specialised settings.

Predictive Equations
Predictive equations like Harris-Benedict or Mifflin-St Jeor estimate daily calories considering resting energy expenditure, typically 1,200 to 1,800 calories for runners. While they factor in general activity levels, these formulas might not fully account for individual metabolism or specific running demands.

Wearables
Wearable devices, popular among runners for tracking calorie burn, can be inaccurate, sometimes underestimating energy expenditure by up to 30%, depending on the model and type of activity. Devices with heart rate monitors generally offer better accuracy than those based only on movement, but they're not foolproof. While useful, wearables should be used alongside other methods for a complete picture of energy use.

Do my energy needs change over time?

Absolutely! Your energy needs change depending on lifestage, training load, changes in occupation and lifestyle and body composition goals.

Changes in Training Load
During high-volume or high-intensity training phases, your body requires more calories, particularly from carbohydrates, to fuel your workouts and aid recovery. In contrast, during tapering or off-season, your energy needs decrease.

Occupational and lifestyle changes
If you transition from a physically demanding job to a more sedentary one, or vice versa, your daily caloric requirements will change accordingly.

Adjusting for Body Composition Goals
If you're aiming to manipulate your body composition — whether it's losing fat or gaining muscle — your energy needs shift. For fat loss, a caloric deficit is necessary, but it must be carefully managed to avoid underfueling. Conversely, muscle gain might require a caloric surplus, emphasising protein intake.

Pregnancy and Breastfeeding
For female runners, pregnancy and breastfeeding significantly increase energy demands to support both the baby's development and the mother's heightened metabolic needs.

Masters-aged Athletes
Active masters-aged athletes often maintain higher energy needs, countering the typical age-related decrease, due to preserved muscle mass and elevated activity levels.

Injury and illness
During injury or illness, your energy requirements may rise to boost immunity and healing. However, this increase is often balanced by a lower training load, potentially leading to an overall decrease in your energy needs.

How do I monitor my energy intake?

You can monitor your energy intake using apps, pen and paper, or spreadsheets. While tracking helps you understand your eating habits, remember that a balanced diet involves more than just counting calories. Adequate protein, carbs, fats, and essential nutrients are crucial. Accurate tracking is key to assessing your diet, but be aware that underreporting in food diaries is common.

Things to watch for when tracking include:

• Misestimating Portion Sizes: It's easy to underestimate the quantity of food consumed, leading to inaccuracies in calorie intake.
• Forgetting to Log Food and Drinks: Small snacks or beverages can add up but are often overlooked in dietary tracking.
• Changed Eating Habits Due to Monitoring: The act of tracking can unconsciously influence food choices and quantities.

How do I know if my energy intake is on track?

Tracking every calorie burned and consumed can be challenging and, for some, may even trigger disordered eating and hinder the ability to respond to natural hunger cues. Instead, focusing on your energy levels, performance, and other physical indicators offers a practical and holistic approach to assess if your energy intake aligns with your needs.

Signs you're not consuming enough energy
Not meeting your body’s energy demands can lead to symptoms like constant hunger or lack of appetite, decreased endurance, strength loss, frequent injuries, illness, training disinterest, slow recovery, fatigue, libido fluctuations, and in women, menstrual changes. These are signs of low energy availability—the state where the body lacks sufficient energy to support all physiological functions alongside physical activity. If this energy deficit persists, it can escalate to Relative Energy Deficiency in Sport (REDs), a more serious condition affecting health and performance. Discover more about underfueling, low energy availability, and REDs by clicking HERE.

Signs your energy intake is on track
To gauge if your energy intake is on point, observe key indicators such as increased endurance, better training responsiveness, and quicker recovery. Fewer injuries, improved sleep, enhanced mental health, and sustained motivation for training are also telling signs. When your energy balance is right, you'll typically feel more robust, train with greater intensity, and experience faster recovery.

Summary

Unlock your full potential by mastering your energy needs, crucial for top-notch health and performance. Learning to accurately gauge and track your energy intake is essential. As an Accredited Sports Dietitian, I'm here to steer you through this. Together, we'll ensure you're always energised, both on the track and in everyday life. Let's fuel your success and help you shine as your best self! 🌟🏃‍♂️💪

To book a performance strategy call to discuss the exact steps to perform at your best for your next big event click here!

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References

Desbrow B et al 2019, 'Nutrition for Special populations: young, female and masters athletes', International journal of Sport Nutrition and Exercise Metabolism, vol. 29, pp. 220-227.

Fuller D et al 2020, 'Reliability and Validity of Commercially Available Wearable Devices for Measuring Steps, Energy Expenditure, and Heart Rate: Systematic Review'

JMIR Mhealth Uhealth, vol.8, iss. 9, e18694.

Mountjoy M et al 2023, 'International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs)' British Journal of Sports Medicine vol. 57, pp.1073-1097.

Murakami H et al 2019, 'Accuracy of 12 Wearable Devices for Estimating Physical Activity Energy Expenditure Using a Metabolic Chamber and the Doubly Labeled Water Method: Validation Study' JMIR Mhealth Uhealth, vol. 7, iss. 8, e13938.

O’Driscoll R et al 2020, 'How well do activity monitors estimate energy expenditure? A systematic review and meta-analysis of the validity of current technologies', Br J Sports Med 2020, vol. 54: pp.332–340.