Energy Availability Explained
Imagine you’re building a house.
Your blueprints are done, permits obtained, and the construction workers have arrived to start Monday morning.
On Wednesday, material deliveries stop.
The electricians are waiting on walls that were never finished. The roof can't go on because the framing isn't complete. Every trade is ready to work, but there simply aren't enough materials.
Now what?
This is a simplified version of a problem that leads athletes and active folks down the google rabbit hole asking “why am I not recovering from workouts?” “Why am I always tired?” and “how do I get my period back?”
Social media might tell you to try seed cycling or intermittent fasting. You might end up chugging energy drinks to make it through the rest of a busy day, but what often gets missed is the driving force behind poor recovery, injury, or missed cycles:
Low Energy Availability.
What is Low Energy Availability?
We have to understand that a body’s first priority is always survival, not necessarily long term health or reproduction. When survival is threatened, bodies often respond in predictable ways.
The demands of physical activity, whether it’s training, walking your dog, or a 5 mile run, will be prioritized because the need is immediate. Whatever is left over goes to the rest of your body: synthesizing enzymes, regulating body temperature, maintaining the cells lining your digestive tract. Your body can mobilize some stored energy to help close the gap, but this effect is short-lived. In as little as two weeks of low energy availability, your body’s purse strings will start to tighten.
When a body attempts to conserve energy, it will often slow digestion in an attempt to absorb more nutrients. Immune cell and red blood cell turnover rate decreases as the body tries to squeeze what it can out of existing molecules. Reproductive hormones are suppressed, which has downstream effects on bone rebuilding, muscle, and cardiovascular health.
This energy conservation effort can also have an effect on mood, motivation, and focus. Generally, athletes are less present at training for a variety of reasons, from decreased immune function to poor recovery leading to injury.
There are a few big reasons that I have found as a sports dietitian that this gets missed.
Here are my top three:
“I’m eating a ton!”
Many athletes are eating a lot and there’s still a gap. This is especially true when meals are made up of things that take up a lot of space but don’t provide caloric density.
Think of what comes to mind for you when you hear the term “empty calories”
Many athletes are striving to eat cleaner, minimally processed foods or cut out dairy or gluten with the hopes of a performance advantage without considering the energy decrease.
Or worse, energy decrease is seen as a positive no matter the circumstances.
What often gets missed is how high energy demands of training can be, especially when stacked on top of the high energy demands of growth or a physically demanding job.
I’ve had athletes eating close to 3,000 calories experiencing issues related to energy availability. While the threshold of symptoms can vary from person to person, a persistent energy deficit of around 250 calories can lead to adaptations associated with energy conservation.
There is also emerging evidence that Low Carbohydrate Availability in the absence of energy deficiency can drive these same symptoms.
We need to look a little more critically at what “a ton” looks like– because it may not be enough, especially if training demands or your dietary pattern has shifted recently.
“I haven’t lost weight!”
While bodies adapt in predictable ways, it can be hard to predict how your body might adapt or where it might be in the time course of energy deficiency.
Here are some common patterns I see clinically:
Athlete has lost ten pounds a year ago, but weight has stagnated.
Athlete’s weight fluctuates 10-15 pounds multiple times throughout the year
Athlete’s weight has been stable but when they stop training, they gain weight relatively quickly.
Athlete’s weight has been stable or increases, along with increases in body fat and/or muscle tissue losses.
Youth athlete’s weight is the same but their height trajectory has flattened
Weight changes can give us a clear sign, but weight changes are not always present. It’s not even considered a guaranteed flag for assessment for REDs (Relative Energy Deficiency in Sport, a symptom-based syndrome that has low energy availability at its core).
An athlete’s weight does not tell us what’s going on underneath the surface, especially if a body is trying to figure out how to exist with less energy coming in. It would be more helpful to measure that specifically, but metabolic testing is still relatively uncommon.
The fact is that bodies of all sizes can be experiencing low energy availability and deserve support.
It’s also worth mentioning that athletes of all levels of competition, from recreational and up, and all age groups can experience low energy availability.
You’re seeing half a dozen specialists but not one is looking at energy availability.
You’re seeing a physical therapist for recurring shin splints. A GI doctor for unexplained IBS and food intolerance. Your PCP is perplexed by your recent sleep problems and increase in anxiety– but no one is considering that energy intake could be contributing.
There are absolutely savvy providers, especially sports medicine or sport-oriented providers who are more familiar with the flags of low energy availability, but most people don’t have training in REDs or there may be bias in whether they look for it at all.
When I, as a college athlete, had missed my cycle for over nine months, my concerns were dismissed by my doctor. I know how frustrating this process can be. It’s part of my mission to reduce the time from onset to recognition with energy issues, but if you have concerns, I highly recommend meeting with a dietitian, ideally a sports RD who is familiar with REDs, to get a second set of eyes on your carbohydrate and energy intake and support you through recovering your physical and reproductive health. Looking back, I wish that I hadn’t had to go through that alone.
Beyond Low Energy Availability
The question I keep asking myself: how do we move beyond this place of preventing issues associated with chronic energy deficiency and towards a place where athletes are benefitting from optimal energy availability?
Much of how we approach nutrition is focused on how we can control and eliminate while missing the biggest piece: how can we make sure the engine is fueled? Are there enough bricks to build the athlete you are to become?
Keeping athletes healthy in sport and for the long game requires a lot of energy and materials, and it doesn’t happen by accident. It happens by challenging the beliefs and systems that encourage restriction and control-based approaches to eating.
Performance nutrition is about so much more than willpower and disciplined eating.
At its core, it must be built on a foundation of enough.
And where most athletes miss the boat is by focusing on what needs to be removed from their diet and what secret, high-level sauce is missing. But what I can say from experience: focusing on adequacy will do more for your performance and health than cutting out oreos or supplement-chasing will ever do.
