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Do You Need More Energy? A Guide to Finding the Right Calorie Balance for Running

Posted Feb 11 2013 6:00am

runner's calorie balanceLast week, we posted two overtraining and low-energy availability related articles, and both highlighted the symptoms and methods for altering training and eating habits to avoid them.

But what if the signs are subtle? How would an athlete know if they are eating enough to support their training and perform their best?

We have a weight-loss focused society, likely due to the prevalence of overweight and obesity issues, and the mindset that we should always burn more calories than we consume is pervasive.

The culture suggests that diets should always yield a negative energy balance because we falsely believe that weight loss will always improve performance and looking good is paramount. But the line between calorie restriction and energy deprivation is not always clear, particularly for athletes.

How much energy do I need?

Our daily energy demands are determined primarily by three factors:

  • Resting Metabolic Rate (RMR) — the at rest energy expended to fuel the vital organs that expends 75 – 80 percent of daily calories.
  • Thermic Effect of Food (TEF) — the energy amount that processes, which is dependent on the meals’ macronutrient composition, but on average is 8 percent of the total daily energy expenditure.
  • Thermic Effect of Exercise (TEE) — the energy that fuels physical activities of daily living, work, and purposeful exercise, the most variable and manageable factor that generally measures 25 – 30 percent of the body’s energy supply.

There are many tools and equations that can be used to predict energy needs. Some are more accurate than others, and some can be very expensive, inconvenient, or simply not available to most athletes. But in general, they are all “predictions” since there is so much variance within an individual on any given day.

If you are trying to figure out your daily energy expenditure on your own, most equations that you find online will serve their purpose, like the Harris-Benedict and the Mifflin St. Jeor equations.

They will give you a general idea of how much energy you would expend just lying in bed (based on weight, height, gender and age) and tell you to multiply that by an activity factor based on how active you are in your daily life (i.e. desk job vs. construction worker). Finally, you will add in an estimated amount of calories you burn doing purposeful exercise (i.e. running, biking, elliptical, weight lifting, etc.).

Many of my clients are surprised when I tell them how much energy they can, and should, consume in a day. Although the body can still perform with lower than optimal fuel availability, matching caloric intake with output is the best way to increase energy and delay fatigue, improve glycogen stores, and achieve peak performance.

Low energy signs and symptoms

As mentioned last week, when energy availability (the amount of energy left over after training) is low, some of the body’s physiological systems may not get enough energy to perform all of their functions. In women, for instance, the reproductive system may be depressed leading to a loss of the menstrual cycle. Women with normal menstrual function as well as men can experience low energy availability also, but the signs and symptoms are less subtle.

Under-eating and over-training signs and symptoms are similar, and since the conditions frequently occur together, may overlap. Common symptoms include:

  • Lingering fatigue and feeling wiped out
  • Poor sleep quality
  • Irritability and low pain tolerance
  • Increased injury incidence or illness
  • Slow recovery
  • Feeling challenged by routine tasks
  • Excessive hunger and “bad” foods cravings unrelated to stress, a lack or willpower, etc., indicating the body is self-preserving
  • Appetite or unexplained weight loss

The biggest problem contributing to under-eating is that a lot of runners don’t have a strong internal connection for matching energy intake with expenditure. Some runs make you hungry while other particularly long or intense runs can suppress your appetite for hours. Internal hunger cues are not enough to tell you if you are getting enough energy.

Energy balance obstacles and solutions

I work with a variety of client types who all have different reasons for why it is difficult to meet daily energy needs.

  1. Underestimating or purposely restricting their calorie needs due to unawareness of physical activity energy expenditure levels, weight loss goals or a fear of gaining weight.
  2. Many runners simply cannot find the time to fuel themselves adequately because in addition to running, a never-ending list of obligations on a daily basis — jobs, kids, housework, projects, etc. — keeps them busy all day.
  3. The enormous energy level some athletes require when logging over 100 miles a week, working out 2-3 times per day for a triathlon or even experiencing a growth spurt for young competitors can be difficult to consume in a day.
  4. Finally, dietary restrictions or illness that restricts food types or stresses the body may increase volume or calorie needs.

Regardless of the reasons for not meeting your energy needs, the solution is pretty simple…make a plan.

Very rarely do you go on a training run without a plan of what you are going to do. Most days you wake up knowing how far you are going to run, the pace you are going to do it at, and the purpose this workout is serving. The same should be true for your approach to nutrition. By having a plan in mind of what you are going to eat, when you are going to eat it and why, you will be better prepared to meet you energy requirements.

If you have had your daily calorie needs calculated for you, you can begin to track your diet to see how well you are meeting those needs. Tracking your diet is a great way to get a sense of how your current diet is contributing to your training and it can also help you practice structuring you meals and snacks throughout the day to make sure your fuel tank is always full.

Yes, it takes work, but just like a good training log, tracking your diet can help identify key areas of improvement.



Loucks AB. Low energy availability in the marathon and other endurance sports. Sports Medicine, 2007; 37(4-5):348-352.

Burke LM, Cox GR, Culmmings NK, et al. Guidelines for daily carbohydrate intake: do athletes achieve them? Sports Medicine, 2001; 31(4):267-299.

Burke LM. Energy needs of athletes. Canadian Journal of Applied Physiology, 2001; 26:S202-S219.

Hinton PS, Sanford TC, Davidson MM, et al. Nutrient intake and dietary behaviors of male and female collegiate athletes. International Journal of Sports Nutrition and Exercise Metabolism, 2004; 14(4):389-405.

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