Energy Availability and making sure you don’t undereat when training

Currently I’m tinkering with my diet, not necessarily the foods but the meal timing and the calorie macros.

It’s not so much that my weight loss has currently stalled. In fact, it did drop to a month-low 168.9 lbs over the weekend… though it has been tough, slow going to move the average down.

I’m trying to naturally maximize my energy levels, which when I’ve fasted had tended to stay low. This means I need more nutrients around these times, which indicates I should stop fasting.

However, I went back through my RRCA training course materials… mostly because I was walking on a treadmill for an hour and the spiral-bound book was one of the only books I had that I could suitably read while on the treadmill. In any case, I went through the information-laden appendicies and it includes a robust booklet on nutrition by the IAAF.

In the IAAF’s Nutrition materials, they mention an interesting stat: Energy availability. The idea of Energy Availability is that aside from calories burned in exercise, the body has a certain number of calories it needs to rebuild and recover from that exercise.

When you take the total calories you’ve eaten in a day, and you subtract the number of calories burned in exercise, the remaining number is your Energy Availability. Let’s say for example (because I actually have done this repeatedly) you eat about 2100 calories. You burn about 750 calories in exercise that day.

2100 total kcal- 750 exercise kcal= 1350 kcal Energy Availability (EAcal)

Now (because this example is me) let’s say you know your weight and body fat %, and you thus you know your lean body mass, since it’s the total mass aside from your body fat. I will also use kilograms here because that’s what the IAAF and the world use to measure mass, and I find humo(u)r in annoying Americans.

77.91 kg – 13.48 kg (17.3%) body fat = 64.43 kg lean mass (kg LBM)

The IAAF’s rule is that if your net energy available is under 30 calories/kg, that is too low, and you’re going to see negative performances and health from such athletes. So let’s take my numbers and see what I get:

1350 EAcal / 64.43 kg LBM = 20.95 Energy Available kcal/kg (EAcal/KG)

Look at that! It’s too low! It needs to be 30.0 EAcal/KG.

That would explain my lethargy, at least during fasting periods, but definitely at any time. Fasting or not, fat burning or not, I (and in turn, our example person above) need to eat more.


We can also reverse-engineer this formula, using my current kg LBM, to figure out the number of EAcal I need in addition to exercise calories to meet my body’s needs.

30.0 minimum needed EAcal/KG) x 64.43 kg LBM = 1933 EAcal

Now that doesn’t mean I can just 1933 calories and I’m good. This does not include any calories burned from exercise. Those subtract from your energy availability. So in this case, I would need to add that 750 calories burned back in to get the total I should have eaten that day.

1933 EAcal + 750 exercise calories = 2683 calories

Now, how can one lose weight eating that much? Obviously I’m trying to lose fat, which is the reason I’m not eating 2700 calories in day. Trust that I have no problem ingesting that many calories. I used to average 3000 and maintain a leaner weight!

Well, the reason I slimmed my diet down was because I was a lot less active. Recall that my life got stressful earlier this year and I could not train/exercise as much. Then of course Coronavirus struck and locked everything down, which made my life more sedentary than ever.

Back then, it made sense to cut calories down to 1700-2200 a day. Even when I could exercise, I was not nearly as active. Eating like before was just going to make me fat, and it was making me fat: I swelled to 184 lbs and over 23% bodyfat before I began reversing the trend.

Now, I’m training regularly again, and while my body is totally up to the volume… I need to once again take in the fuel to match it or I get the low energy I’m currently experiencing.

So now, take today. I went on a 3.4 mile run this morning that burned 380 calories. Let’s say later today I’m going to go strength training, which for certain will burn 120 calories… possibly more, but let’s just say 120.

380 run kcal + 120 swolework kcal = 500 total exercise kcal (EXcal)

I can take my baseline EAcal and add it to these numbers to get the total number I need for today.

1933 EAcal + 500 EXcal = 2433 minimum calories needed today

Note also that my EAcal is not exactly my basal metabolic rate (BMR), the minimum calories my body will burn today. That number is more like 2050 calories. So, if I were to just eat the 2433 minimum calories, I would still finish with a slight calorie deficit.

So my fat loss should continue even if I’m eating more calories. Notice this does not include any additional, incidental calories burned from everyday activity (random walking and other physical effort). I just need the minimum calories to maintain my energy level and overall recovery.

Also, side note, weight loss can also come from any loss of water weight or other biomatter, and as you burn fat and eat healthy, you tap into and clear some of that extra weight.

So, I just need to eat more, and it just needs to match my activity level for the day. Probably easier said than done if training substantially varies from day to day.

Part of my progress right now is to increase and reduce the variance of that volume. My current goal is to train or be otherwise active for a total of at least an hour a day. Once I know I’m burning 500-1000 calories a day for sure, that provides a solid minimum calorie total and makes meal planning a lot easier.

In any case, finding your EAcal can help you establish an intake baseline that will keep your energy high and your training productive and healthy.

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2 thoughts on “Energy Availability and making sure you don’t undereat when training

  1. […] sizable calorie deficit, and focused on eating closer to maintenance calories, to ensure I had the energy availability to train. I had felt more sluggish while intermittent fasting and eating at a deficit than I have […]

  2. […] focusing more on fueling for recovery and eating to a minimum of energy availability. This leads to a slight calorie deficit when I hit the minimum calories, though I’ve still […]

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