What is Energy Availability?

Many people are reasonably comfortable when talking about nutrition and fuelling to refer to a version of the Total Daily Energy Equation, commonly referred to as Energy in = Energy out. The energy requirement that a person needs are worked out given a person’s resting metabolic rate, Physical Activity Level, Non-Exercises Activity Thermogenesis, Food-related Thermogenesis and Exercise Expenditure is balanced with the individual’s daily dietary intake. However, there is little discussion around Energy Availability. The TDEE approach considers a person needs energy for bodily functions, and whatever is left can be managed through eating enough for their exercise. To lose weight, you eat less than you need to move and to gain weight; you are eating more than you can expend. It is reasonably straightforward, but this simplicity can undermine it.

Energy Availability and the associated conversations flip the approach around and, for athletes, puts the exercise expenditure first. The body uses the energy for exercise and then uses whatever is left for bodily functions. This leftover energy after exercise is called Energy Availability. There isn’t a deficit or a surplus, there is just whatever is left, and your body will use it to survive. As we have to put health before fitness, then ensuring there is enough to survive is critical to athletic long-term success and enjoyment of the sport.

This makes sense practically, as the individual will do a gym session or run. They may not quite hit their targets, but they can move! The leftover energy then has to be spread amongst your body’s energy needs.

It has been shown that if there is not enough left over for “normal” functions, your body can go into “power saving” mode (a bit like your phone) and prioritise certain functions and downregulate others. In other words, your body is not operating optimally for performance. Instead, it is working to conserve energy. This then leads to a reduced Resting Metabolic Rate (RMR) as the body strives to find a new Energy Balance.

Calculations and limits

The generally accepted calculation is that:

Energy Availability = (Calories Consumed – Exercise Calories Burned) / Fat-Free Mass

The recommended target is for energy availability 40-45kCal/Kg Bodyweight for healthy function. We can use this to estimate how many calories you need to consume on top of your training or exercise calories on any given day (see the tables below). There is also a clear limit of 30kCal/KgBW for women, and 25Kcal/KgBW for men were below that available energy, the body goes into its power-saving mode. This limit is called Low Energy Availability, and any duration over four days at LEA can produce significant detrimental down regulations of essential bodily functions and systems. Over time, this is then diagnosed as RED-S (formerly the female athlete triad). For endurance athletes, aside from ignoring the importance of a person’s health, it can lead to low bone density and ultimately stress fractures and increased cortisol, fat retention and mood swings/motivations slumps.

Evidence suggests that hourly Energy Availability amounts are also critical to training consistency over a prolonged period. Therefore, ensuring that an athlete has enough energy throughout the whole day is also essential.

Unfortunately, the LEA limit can be reached accidentally quite quickly. As the first response is for the body to lose weight (usually muscle) to facilitate glycogen production as a fuel source, performances are likely to improve before any detrimental effects are seen. All the performance reductions occur in the body’s functions rather than the sport-specific actions. It is doubtful we will see any of these responses. This can mask the process for achieving those performance gains and lead both the athlete and the coach into a false sense of security.

What does this look like for me?

The implications of looking at the Energy availability approach rather than the traditional Energy in = Energy out method is that we can see that we can be in energy balance but be unhealthy.

If we take the above examples of a 35-year-old male and female who weighs 85kg and 60kg, respectively, we can see how the EA target is significantly higher than the TDEE, and requirements change based on their body composition. It means that purely working off Calories in v Calories out could be misleading, and if they were under on a day, there was a significant likelihood that they would be touching on the LEA limit. For endurance athletes on big days of training or multiple sessions in a day, this could mean athletes unknowingly are causing themselves to be in a state of LEA and causing the resultant negative responses.

Weight loss and getting “lean.”

Many people start sport for aesthetical reasons rather than performance ones, and we can address both through the EA approach. Firstly, traditional diets will put someone into a form of calorie restriction, are likely to put someone into LEA and sustain that for a prolonged period. As we mentioned above, your body responds by becoming more efficient or choosing the essential bodily functions. This means the body reaches another point of balance by reducing the calorie requirement to remain healthy (which it is not at this point), and weight loss does not continue. The individual must do another calorie restriction to see further weight reduction, and this can end in a continual cycle or race to the bottom. When additional or normal eating resumes, the body’s Resting Metabolic rate increases again as all the systems are used fully and the weight bounces back up! There are countless papers on how this can lead to eating disorders.

Nevertheless, weight loss in sport for performance is something that can be managed and periodised into training. However, it has to be done carefully, under the management of a professional and to keep the athlete’s energy availability high. The purpose of this style of weight loss is to reduce the fat mass and not reduce the muscle mass at all. Higher protein intake would be required, and training loads would need to be managed carefully. Often, this is not something that can be sustained throughout a season. Successful athletes deliberately drop into “leaner” periods for races but do so without significant calorie restrictions and over a long time (targeting ~0.7% of Bodyweight per week). This may be something amateurs look to do as well. However, the reality is that there are probably several lower hanging fruits to target before a deliberate attempt to drop into unhealthy body fat ranges for a key date or race! There are many other lower-risk options to consider!

Though there is minimal research into Energy Availability style weight management programmes, the current suggestions are to keep EA at about 30-40kCal/KgBW to enable a slight deficit but continued performance and training effect for a targeted and brief time. This can be considered for amateur athletes looking to generally lose weight as part of a health initiative and continue training effectively.

How will Energy Availability Change your approach?

Energy availability is worth considering as well as an energy balance equation. Ultimately, we are surrounded by stress and pressure to look and conform to the endurance athlete stereotype. Coaches and other sources of comparison can exacerbate this. However, health must always come before fitness. Have a moment to calculate your own energy availability requirements using the Equation above and then targe that amount of fuel through the day and eat for your training. If you can get that right, you are likely to hit the required health levels for optimised bodily functions and subsequently be able to avoid injury and train effectively and consistently throughout several seasons. Consistency has been the most significant indicator of success in sport above and beyond any weight-related performance correlation!

This article was first published on the Tri Training Harder Blog –?click here to read the original or see?more articles?like this one.