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Energy Expenditure Explained

‘Energy cannot be created or destroyed, only transferred from one form to another’

This is the first law of thermodynamics, which is a key principle from the laws of physics which governs energy.

What do we mean by energy?

Food and drink contain potential energy, measured in Calories which we use to fuel our everyday actions.

As the first law of thermodynamics suggests, we can’t create this energy for our bodies out of nothing, so energy transfers from food and drink to our bodies to enable us to function and carry out everyday activities.

Have you ever wondered why when you look at food packing calories comes under ‘energy’?

That is because a calorie isn’t a physical object, rather a measurement of heat.

One calorie is the amount of energy required to heat one gram of water by one degree Celsius.

The calorie content is often given in kcals, which is short for kilocalories and is just another word for Calories. So, 1,000 Calories will be written as 1,000 kcal.

Energy Balance

The energy balance equation describes the relationship between energy intake and energy output.


Energy in – number of Kcals you consume each day from food and drink

Energy out – is your Total Daily Expenditure (TDEE) and can be divided into Resting Energy Expenditure (REE), Non-Resting energy Expenditure (NREE). 

REE refers to the amount of energy you expend at rest, consisting of our Resting or Basal Metabolic Rate (RMR/BMR). The slight difference in these is that RMR is measured from a non-fasted state (your body requires energy to digest and assimilate food, so this figure is the higher of the two), whereas BMR is measured fasted.

Your RMR/BMR is the amount of energy your body needs to maintain basic internal functions at rest, such as your heart rate and breathing. 

This accounts for between 50-70% of your TDEE, depending on how active you are.

In a sedentary person, this will account for a higher proportion than someone who is active, as shown below: 

NREE contains three elements:

1.      Thermic Effect of Food (TEF) – all foods require a certain amount of energy to digest and process for usage and storage in the body. TEF accounts for ~10% of TDEE, assuming a balanced diet is had. This is sometimes why you hear people refer to certain foods as ‘fat burning’. Often this means their TEF is higher on the spectrum, but it’s important to remember that these are not fat burning superfoods and all their other macros need to be ignored!

2.      Thermic Effect of Activity (TEA) – the energy required to perform purposeful exercise such as your Barn Bootcamp or PT sessions. This can vary a lot depending on activity levels of the individual. Anywhere from 0% if totally inactive, to 50% if extremely active.

3.      Non-Exercise Activity Thermogenesis (NEAT) – the energy required to perform non-purposeful, unplanned and low-intensity activity of everyday life such as walking to the shops, cleaning the house, climbing stairs and fidgeting! This is often overlooked but is incredibly important when thinking about energy expenditure, as it counts for up to 30%. This is one of the reasons at The Barn Bootcamp we set you a step target (in conjunction with the great mental health benefits that come with getting out in the fresh air).

But what can we control? 

Sadly, we can’t influence the TEF of food, and it is such a small proportion of the overall energy expenditure it is not worth stressing over. 

We can certainly control the amount of purposeful exercise we do. Find a routine that works for you but hitting 3-5 sessions per week is within your control and something to strive for. 

However, there is only so much purposeful activity you can do where you ensure you have enough recovery time to be able to perform effectively and safely.

This is where your NEAT becomes a huge controllable factor. 

Often, people assume that exercise is the biggest energy expander, so as long as they do their 1-hour session, movement for that day is checked off the list. 

But when we look at the above graph, we can see that your NEAT accounts for a far greater percentage of your overall energy expenditure. 

That 1 hour accounts for just 4% of your day. 

Let’s say on average you sleep for 8 hours a night (I know, I wish it was that long too…) you’ve got roughly 60% of your day left. 

Understandably, not every minute of that time can be spent being active. 

Jobs, family, relaxing time, meal times all are important factors in everyday life. 

But increasing your movement where possible is a sure-fire way to improve your overall health, and contribute to your weight loss if that is your goal. 

Every day is different. 

Not only does each day change in terms of external factors, but our internal functions will also be slightly different too. 

This is why tracking key data such as your weight, food intake, steps and exercise sessions regularly allow for you to take an average overtime, giving you a more accurate picture of how your body is responding.

Dissecting the Balance Equation

When in a state of energy balance, where energy in = energy out, means there is no change in your body’s energy stores, which is often referred to as ‘maintenance’. You may have heard someone say they are on ‘maintenance calories’ this is what they are referring to. 

A positive energy balance refers to when your energy intake is more than your energy output, known as an ‘energy surplus’. This surplus in energy must go somewhere, as it cannot be destroyed, so your body stores it as a combination of FM and LBM. In which way it is stored is influenced by a few factors, including quality of your nutrition and activity level and type. 

A negative energy balance refers to when energy output exceeds energy intake, known as an ‘energy deficit’. In this instance, your body needs more energy than is being used and seeing as it cannot create energy, it must break down and rely on your stored energy in the form of FM and LBM. 

Average energy expenditure must be greater than average energy intake for optimal fat loss.

Average energy intake must exceed average energy expenditure for optimal muscle gain.

Average energy intake must equal average energy expenditure for maintenance.

Note the use of the term ‘average’ in the above statements.

Energy balance does not reset each day. It does not start at midnight and end 24 hours later.

If you create a small energy deficit on weekdays but spend the weekend in a large energy surplus, then it’s likely your weekly average energy balance is going to show you in an energy surplus.

In other words, making sound nutritional decisions and eating to serve your goal during the week but taking an ‘oh well, it’s the weekend attitude’ for 2/3 days, is probably stopping you from making the progress you want.

Take a look at our article ‘Why Am I Not Progressing Towards My Goals’ for a breakdown of how to manage weekly calorie targets.

What do we mean by ‘Change in Body Stores’?

The energy balance equation predicts changes in the energy stores of your body.

We can think of this as Fat Mass (FM) and Lean Body Mass (LBM).

The energy balance equation must always be balanced.

Therefore, if energy in exceeds energy out, your body balances the equation by storing the excess energy as a combination of FM and LBM.

On the reverse, if energy out exceeds energy in, your body balances the equation by breaking down FM and LBM to release the extra energy it needs.

It’s important to remember there are lots of factors that affect body weight outside of simply energy in v energy out.

Stress levels, glycogen levels, inflammation and the female cycle can affect the way in which the body holds onto water, therefore, influencing body weight independent of what changes may have occurred to FM and LBM.

Personalised Calorie and Macronutrient Targets

Based on the above points, even if you were to eat the exact same as another person, the outcome and whether you are in an energy surplus, deficit or at maintenance will be different.

And at the end of the day…we are human (in case you have forgotten).

We are all different!

This is why you receive a personalised nutrition plan at The Barn Bootcamp.

When creating this, we estimate your BMR/RMR, which is going to be different for everyone and takes into account your age, gender, height.

Your estimated activity levels are considered.

We then look to create a deficit or surplus, depending on your goals.

We look at what your maintenance calories would be, then set your deficit/surplus as a percentage of that maintenance number.

It’s important to know that an aggressive (high % deficit/surplus) may give you quicker results, but is likely to be unsustainable and potentially have a negative effect on your holistic health.

A good place to start is with a 10-20% deficit/surplus.

The appropriate level will be influenced by your training age (how many years you’ve been training), your current nutritional habits, your current FM and LBM and your timeframe.

At The Barn Bootcamp, a sustainable diet and training programme is at the forefront of everything we do.

This is because good nutritional choices and working hard in the gym is something we want you to be able to do forever.

We don’t want it to be a quick, temporary solution…we want this to be lifelong. 

Creating sustainable habits, where recovery is good, energy is high and you feel fulfilled with life is vital to us, and it should be to you.

As mentioned above, there are many factors considered when setting your calorie goal.

Therefore, as you progress towards your goal, your target might change.

How your weight is responding, how your energy levels are, how you are sleeping, how you are performing all need to constantly be monitored to ensure your targets are appropriate to your goal.

We give you a rate of change table to help you understand where we expect you to be at each stage of the journey. 

This helps you to stay focused and check if you are progressing in the way you want. 

Need help with getting your journey started? Click ‘Enquire Now’ to speak to a member of the team.

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