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Energy Availability and Relative Energy Deficiency

Performance Training Personal Training

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Once we have established the foundations of our Energy In vs Energy Out equation, we can begin to look deeper at the implications of this in practice. 

Hopefully we can now appreciate from our previous post, how multifactorial this simple statement is on both sides of the equation. 

The manner in which our food intake is regulated through physical, cultural and environmental factors, controls both our appetite, hunger and satiety signalling. Likewise our energy expenditure is contributed to by our basal metabolic rate (BMRwhat it takes to keep basic functions up and running) the thermic effect of the food we eat (TEFthe energy it takes to break down food), our non-exercise activity thermogenesis (NEAThow much we move…) and finally our exercise activity thermogenesis (EATstructured exercise).

With these factors in place, we can begin to establish what types of approaches may be beneficial to optimise both the levels of energy intake and expenditure over the long term.

We’ll consider these as four separate combinations, each of which will have potential positive and negative consequences on an individuals health, performance and body composition. In each of these scenarios it’s possible to see variations other than the aforementioned, depending on the starting conditions, however this provides a broad contextual overview to begin.

  1. Reduce Energy In and Increase Energy Out (i.e. caloric deficit via increased expenditure)
  2. Reduce Energy In and Reduce Energy Out (i.e. maintenance through sedentary lifestyle and minimal intake)
  3. Increase Energy In and Reduce Energy Out (i.e. caloric surplus via increased intake
  4. Increase Energy In and Increase Energy Out (i.e. maintenance through high energy flux)

Let’s take each one of these scenarios in turn and see what the likely outcomes will be.

Reduce Energy In and Increase Energy Out

In this scenario, the initial outcome is quite clear when it comes to overall energy balance. We’re reducing the amount of energy coming into the system, whilst simultaneously increasing energy expenditure. Assuming this is sufficient to create a caloric deficit, we will likely see a negative trend in body composition and resultant weight loss over time. 

The speed at which this occurs will be dependent upon the magnitude of the caloric deficit. For example a deficit of 250kcals over an extended period of time will result in a slower pace of weight loss than a 500kcal deficit. 

The magnitude of deficit, type of tissue lost, whether this be predominately adipose tissue (body fat), muscle mass, glycogen or water retention will all be the subject of future posts. However the frist  is to recognise the creation of a caloric deficit via a positive increase in energy expenditure over caloric intake.

Reduce Energy In and Reduce Energy Out

In our second scenario we have a reduction in both sides of the equation, both energy intake and expenditure, resulting in maintenance of bodyweight through minimal intake and expenditure. 

Maintenance through sedentary lifestyle and minimal intake

If we consider this from our energy expenditure contributing factors, BMR, TEF, NEAT and EAT, our capacity to change BMR is small in scope likely only to be effected by and increase in lean body mass or change by hormonal contributors such as thyroid hormone. TEF, whilst contributing potentially between ~10-20% of total TDEE is unlikely to alter much in the presence of a relatively whole food diet. EAT may potentially contribute a +/- difference of 150-250kcals above expected calorie burn when performed. Therefore NEAT is likely to be the most impacted variable due to it’s wide-reaching impact on total daily energy expenditure. 

We likely will have experienced this effect ourselves to some degree, on days in which we may have missed a meal or two, or attempted to exercise having been under-fuelled.  Feeling lethargic, unwilling to move from the sofa, the reduction in overall daily movement. We fidget less, we’re less expressive, less talkative, all of which can be acute symptoms of reduced energy intake.

Whilst this may create a scenario in which bodyweight is unchanging over time, achieving a degree of energy balance, this is can’t really be considered optimal in terms of maintaining or enhancing health over the long term.

Increase Energy In and Reduce Energy Out

This scenario is the reverse of our first example, we’re consequentially going to see the reverse outcomes at play. When we increase energy intake and simultaneously reduce energy expenditure to a degree that it creates a caloric surplus, we will like see upward trend in bodyweight over time. 

Again, the speed at which this occurs is dependent on the magnitude of the change consistently over time. To see prolonged weight gain in the long term, this equation needs to be continually in favour on energy intake exceeding expenditure. 

The immediate and longer term effects of this scenario do raise some interesting observations in an organism aiming to maintain homeostasis. 

Continual energy intake above expenditure is likely to result in a marginal increase in BMR, remembering that lean body mass and hormonal status are contributing factors t0 BMR, both of which will be positively increased by a reasonable caloric surplus.

We would also expect to see a small increase in TEF with more food likely now being consumed in a surplus.

Possibly counterintuitively to our current experiences, this should also be in addition to an overall increase in NEAT, due to the presence of a caloric surplus providing more energy in the system, resulting in more total daily movement.

With more energy being consumed, to maintain equilibrium, we should want to move more.

However as we’re increasingly seeing in most Westernised individuals within an environment that requires little activity on a day-to-day basis, an increasing reliance on technology, a food environment that creates heavily processed and calorically dense food choices at minimal cost or effort to obtain, our energy intake is far exceeding expenditure even in light of this expected increase in NEAT. This is a topic we will expand upon in future insights as we progress through this field of discussion.

Increase Energy In and Increase Energy Out

Our final example provides what could be the ideal situation long-term for individuals looking to maximise health, performance and body composition targets. 

In this scenario, our goal is to maximise the amount of energy we intake whilst simultaneously increasing, and subsequently maintaining, higher levels of energy expenditure. 

* A brief caveat that should be considered here is the potential separation between health and performance. This is a N=1 scenario. High levels of energy expenditure is context dependent. An Olympic Swimmer training 4-6 hours a day, with multiple daily sessions, 5-6 days a week, is likely to require extreme levels of caloric intake to match the high degree of energy expenditure. It is not uncommon for these types of individuals to consume 4000-5000kcals and above, on a daily basis. This type of energy expenditure would be above the threshold of what many individuals would classify as a high level of energy expenditure.

Application into Case Study Examples

To provide some clear demonstration and practical application, let’s introduce a case study example to work from.

A 35 year old female, 165cm tall, currently weighs 65kg. To begin with, we’ll say she has a sedentary desk job requiring minimal physical activity and doesn’t currently take part in any structured exercise.

If we use a simple online calculator for BMR and total daily energy expenditure (TDEE) (https://www.omnicalculator.com/health/bmr-harris-benedict-equation) to establish a rough estimation, we can create the following scenarios for her…

At 65kg, 165cm, 35 years old, and female in gender, we have an estimation of BMR equalling ~1408kcal per day*

(*remember this number is only an estimation based on a reference population and will fluctuate by as much as +/- 200-300kcal+ depending on the individual).

From this, if we then determine total daily energy expenditure (TDEE) by factoring in our lowest level of physical activity, sedentary (little to no activity), we reach a total daily energy requirement of 1690kcals (TDEE = BMR x1.2).

Appreciating that these are purely estimations and likely to require individual personalisation, this would create a situation of energy balance through a sedentary lifestyle in the presence of caloric maintenance.

Moving very little but not over-consuming resulting in weight stability long term…

Let’s walk this client through the four scenarios outlined above, beginning with Reduce Energy In and Increase Energy Out.

In this example we will reduce her energy input and increase her energy output. To begin, let’s take away the often promoted 500kcals deficit from energy intake and see where this leaves her (Reduce Energy In)

Our client is now consuming 1190kcals per day, just from our reduction in daily food intake.(1690-500kcal)

Now let’s add in that increase in energy expenditure as well, moving from sedentary (BMR x 1.2) towards a moderate physical activity level with 2-3 exercise classes per week and a regulated daily step count of ~7000 steps (BMR x1.55). 

Her estimated TDEE has now moved up to 2183kcals a difference of 397kcals. In this scenario we’re not adding that back in to create maintenance, but taking it away… (Increase Energy Out).

So 397kcals of increased daily movement and exercise taken from 1190kcals leaves her with an actual caloric intake of 793kcals per day… We’ve now heavily shifted the balance into a calorie surplus by reducing both intake and increasing expenditure.

Understanding Relative Energy Deficiency (RED)

It’s at this point I’d like to briefly switch gears and introduce a concept called Relative Energy Deficiency often shortened to RED, or within a sporting context RED-S (Relative Energy Deficiency in Sport).

RED is defined by Mountjoy et al. (2014) in the International Olympic Committees consensus paper as, “impaired physiological function including, but not limited to, metabolic rate, menstrual function, bone health, immunity, protein synthesis, cardiovascular health caused by relative energy deficiency”

Simply put, we need energy intake to support our most basic levels of function. When caloric intake is at such a low degree that it can no longer support these requirements, we may see a series of underlying health conditions occur that impact physiological function at the most basic levels.

Mountjoy et al. (2018) in a subsequent update established that “many physiological systems are substantially perturbed at an energy availability of <30 kcal/kg FFM/day.” 

For our female example above, let’s factor in one additional requirement to enable us to see where she falls against this low energy risk factor by adding in an additional estimation of body fat percentage. 

To ensure that we use both use an example with enough body fat percentage to maintain a menstrual cycle – (this will be personal to the individual), and realistic for the context of this case study, let’s assume she’s ~25% body fat. 

65kg in total bodyweight with ~25% being adipose tissue. That means she has ~48.75kg of fat-free mass on her physical frame. 

If we now multiply this by Mountjoy et al.’s recommendation for remaining above 30kcal/kg of FFM for long term health outcomes, we get a minimal caloric intake above the threshold for the associated health complications of RED, equalling 1462kcals.

A recommendation of no lower than 1462kcals, vs a proposed strategy utilising a daily intake of 792kcals through reducing energy intake and increasing energy expenditure.

Just based off of these numbers, by introducing a 500kcal deficit and simultaneously increasing energy expenditure from sedentary – (little to no activity/exercise) to a moderate level (~7000 steps and 2-3 exercise classes per week), we’ve created an overall caloric intake of ~793kcals. We’re clearly running the risk with this individuals health in maintaining basic physiological functioning in the time duration of this scenario.

We likely in this circumstance will see significant weight loss occur, simply due to the presence of such a severe caloric deficit. But is there any degree of sustainability in maintaining this and not directly impacting negatively on other health parameters?

Context does however matter. If our goal with this individual was a reduction in body composition through a short term intervention for a valid, ethical and moral purpose, this is type of approach is likely going to be the modality of choice to create a caloric surplus.

However we would no doubt need to re-evaluate any recommendations to move forward successfully long-term.

These types of approaches should be undertaken with the guidance of a trained professional, with clear intentions, outcomes and timescales, aware of the symptoms and possible long term consequences of extended periods of caloric deficit below recommendations for RED. 

This should NOT be considered a long term nutritional strategy.

So where does this leave us in the context of our remaining scenario’s we began our insight with…

Reduce Energy In and Reduce Energy Out Revisited

Sedentary with minimal caloric intake.

An estimated BMR of ~1408kcal, increases fractionally to ~1690kcal when we factor in minimal activity and/or exercise. Above our recommendation of ~1462kcal for RED risk, but not by much (34.6kcal/kg/FFM/day). Even though we’re at possible weight-maintenance levels, we may begin to see signs and symptoms of associated with RED in this individual.

Say this individual choses to lose a small amount of bodyweight using a caloric deficit strategy (either intake or expenditure) from above, we now add in the same 500kcal deficit as before to create 1190kcal of daily intake.

Having been on the cusp before, this is defiantly going to push her below our RED recommendation (no lower than 30kcal/kg/FFM/day) of ~1462kcal. 

OK… let’s halve the deficit to 250kcal totalling 1440kcal, and we’re still below/on the threshold… this just isn’t going to work in the context of this scenario. 

We can’t safely and ethically utilise any model of reducing energy intake and reducing energy expenditure without moving below the barrier for RED in this individual. This isn’t going to be an effective long term strategy.

Increase Energy In and Reduce Energy Out Revisited

Let’s begin here by first asking a question. Is there an optimal level of caloric intake in relation to RED? A possible threshold at which we can start to build from?

In the same Mountjoy et al. (2018) research paper, they highlighted how… “rigorously controlled laboratory trials in women have shown that optimal energy availability for healthy physiological function is typically achieved at an EA (*energy availability) of 45 kcal/kg FFM/day.”

Let’s use this as our staring point, 45kcal/kg/FFM/day and build from there.

45kcal multiplied by 48.75kg FFM (65kg – 25% BF) gives us a daily caloric intake of 2193kcal. Target set…

Let’s use our moderate physical activity example for our female individual who achieves ~7000 steps per day as well as 2-3 exercise classes per week, her estimated total daily energy expenditure was 2183kcals…

We’re within 10kcals in this scenario. Without changing anything else (and recognising these are just numbers with wide ranging variations between individuals…) we’ve got a pretty accurate starting point.

If I wanted to maximise this individuals caloric intake in relation to both RED risk, ability to achieve consistent levels of NEAT and the ability to take part in regular EAT, we’ve stumbled upon a pretty good starting point here. We’ve may have reached a potential energy balance in a positive health and activity balance (possibly needing to +/- 200-300kcals depending on the “real” person).

To create our scenario above, in which our goal is to increase or decrease energy intake above expenditure, we can simply add or subtract in an additional 250-500kcal to create that tipping of the scales in terms of sustainable weight gain or weight loss.

This leaves us with our final scenario…

Increase Energy Intake and Increase Energy Out Revisited

We’ve already touched on the implications of this approach briefly in the context of our last example. How taking an individual from minimal intake and minimal expenditure towards a very achievable ~7000 steps per day and 2-3 exercise classes, opens up a much greater window above the threshold for RED to make sustainable changes in body composition long term without sacrificing health or potential performance adaptations.

However we can look at one brief final situation and finish with a more long-term outlook.

Firstly, let’s keep to our same female avatar and just simply increase her physical activity further to see what the requirements would be if we brought her in line with someone with a physical job and multiple exercise sessions per week (6-7x).

A conservative estimate would be ~2676kcals, depending on the type of job and training, this could likely be a conservative underestimate of the needed energy intake to maintain energy balance before we factor in any errors with the calculations (likely to be +/- 250-500kcals at an individual level).

In terms of RED risk we’re close to 55kcals per kg/FFM/day, 10kcals  per kg/FFM/day higher than the potential “optimal” threshold. She’s at no percievable risk with this level of energy intake in spite of the large energy expenditure due to the increased energy intake above recommended levels.

Now consuming this amount of food on a regular basis in the context of this level of physical activity is going to offer its own challenges and will be something we discuss in more details in future posts, however seeing the contrast between just three examples, reduced intake and expenditure (793kcal), achieving 45kcal/kg/FFM/day in the context of ~7000 steps and 2-3 exercise classes per week, and how upper levels of daily physical activity and exercise require much greater levels of intake due to the significant increases in expenditure in preventing RED risk and achieving energy maintenance, shows just how complex dealing with nutrition can be. 

The four scenarios we began with, all play out on a daily basis in our own lives and those of others. We will each likely fall within one of these categories and move between them across the lifespan.

However if there is one situation that is likely to be the long-term goal in establishing energy maintenance in an optimal way it would be our high energy-flux scenario of increasing energy intake and expenditure. 

Our goal should be to move more and subsequently eat more!!

How, therefore can we get an individual to consume as much energy as possible, remaining weight stable over the long term whilst supporting basic health (BMR), regular whole-food intake, (TEF), and an active lifestyle (NEAT) that may (or possibly should…?) include some form of regular structured exercise (EAT).

Finding this caloric maintenance in the context of our habitual physical activity and exercise levels, and seeing how high we can take it, is a vital tool to have.

From here we have the capacity to move between deficit, maintenance and surplus at our will, safely.

It benefits us hugely to remember that there are risks in living in low energy intake, or high energy expenditure situations when it isn’t counterbalanced in the context of relative energy deficiency and it’s associated health risks.

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