Calories out (or energy expenditure if you’re feeling fancy) is a pivotal factor influencing our energy balance. There are a number of factors that govern energy expenditure, and some are more influential than others. This article will detail the main components of our energy expenditure.

Total Daily Energy Expenditure (TDEE)

Total Daily Energy Expenditure is the amount of energy we use per day. It is comprised of:

  1. Basal Metabolic Rate (BMR)
  2. Non-Exercise Activity Thermogenesis (NEAT)
  3. Exercise Activity Thermogenesis (EAT).
  4. Thermic Effect of Feeding (TEF)

I will discuss each of these components in further detail below. The chart below shows the weighting each component has on our overall energy expenditure. Obviously, this weighting can differ from person to person. More active individuals may find that their EAT contributes more to their TDEE than that of a more sedentary individual, for example.

Using data from Maclean et al. (2011)[1].

#1: Basal Metabolic Rate (BMR)

Basal Metabolic Rate (BMR) tends to be the most influential component on our TDEE. It is sometimes also referred to as Resting Metabolic Rate (RMR) or Resting Energy Expenditure (REE). RMR is slightly different, and will be covered at a later stage.

BMR is the daily amount of energy used by the body to carry out basic functions. Basically, the energy you use to keep yourself alive; heart pumping, lungs working and muscles contracting to name but a few. It makes sense that this is the highest contributor to our energy expenditure when you consider the amount of tasks we do in a day on autopilot. You literally burn these calories by sitting on your arse. Nice. Why would you even need to exercise when you can torch those calories with no effort?

There are a number of ways to calculate your own BMR. The most accurate way involves a lab test[2] . Ain’t nobody got time for that. Alternatively, you can calculate your own BMR by using the Harris-Benedict formula here. This will take into account your height, weight and gender. It’s also a lot more convenient.

Those of you who have ever tried super low calorie diets, or tried any form of restrictive diet aimed at cutting as many calories as possible, may be surprised by your BMR, and the fact you were most likely eating well below it. At some point in your life, you have followed these diets that don’t let you eat enough to keep your BASIC VITAL FUNCTIONS ALIVE. Why on earth should people be allowed DO THAT JESUS FKN CHRIST. (But that’s a whole different rant). If you eat below your BMR consistently over time, it makes sense that you will suffer the consequences. You will find it hard to stick to these low calories, as shockingly your body is trying to keep you ALIVE, so you will suffer increased hunger etc. And rightly so. It is not you having “no willpower”. It’s not that you are “weak”. It’s just that this approach ain’t it, sis.

#2: Non-Exercise Activity Thermogenesis (NEAT)

What is the name given to activity that isn’t directly planned exercise, such as fidgeting, cleaning and walking around?

Marge always knows.

As you can see from the pie chart above, NEAT is the second most influential factor on TDEE for most people. However, NEAT tends to be the factor that varies the most between individuals[3].

Your NEAT can be largely influenced by your lifestyle and environment. If you sit at a desk all day, take the lift instead of the stairs and drive to work, your NEAT will be significantly lower than someone who works in manual labour for example.

We have huge power to control our NEAT, and it is living proof of small changes over time making a massive impact. For example, if you parked a little further from your workplace and walked for an extra ten minutes, over time this would help increase your NEAT. You could increase your energy expenditure, and you wouldn’t even know it! NEAT tends to be naturally regulated by the body with energy intake. It tends to go down in periods of lower caloric intake[3]. You may notice this if you have ever restricted your caloric intake significantly. All of life’s everyday tasks become difficult. You don’t want to walk up the stairs, play with your kids or even simply make your bed. Your body is trying to make do with this lower energy intake; it makes sense that it would try and limit any “non-essential” energy output.

#3: Exercise-Activity Thermogenesis (EAT)

When we think calorie burning, we tend to assume that our planned exercise sessions are the main factor. You can see from the chart above that it is not the case. Planned exercise sessions really only contribute to a small amount of our TDEE. Obviously, for some individuals such as athletes who are training multiple times a day it can be more impactful. But for the average individual, while it certainly contributes, it is not the make or break of your TDEE.

#4: Thermic Effect of Feeding

Burn Calories by Eating: Oxymoron or the Greatest Life Hack?

TEF is the increase in energy expenditure after we take in and digest food. It is the smallest stand-alone contributor to TDEE (we tend to group NEAT and EAT together when discussing TDEE). For most people, it accounts for roughly 10% of our energy expenditure[4].

It is influenced by the energy content and macronutrient ratio of food. Different macronutrients require different amounts of energy, so that they can be metabolised and stored. Protein can stimulate TEF by 20-30% and has the highest impact on this. Carbohydrates and fat influence it by 5-10% and 0-3% respectively[5].

You might read this and think; “Sweet, just eat loads of protein and I’ll become a calorie-torching machine.” Yes, we use more energy to digest protein than any other macronutrient, but this only marginally influences our energy output. You would be better placed in focusing your energy on manipulating other more impactful elements of energy expenditure.

Conclusion

Creating a calorie deficit requires consideration of a large number of factors. Our energy output is controlled by a number of different factors, which vary in impact from person to person. Your energy output is unique to you.

I hope by reading this you have gained an appreciation for this, and realise that while technically it is “calories in, calories out” bro, it’s not always that simple.

Any questions/comments leave them below, and if I have forgotten something/misworded something please let me know!

References

  1. Maclean PS, Bergouignan A, Cornier MA, Jackman MR (2011) ‘Biology’s response to dieting: the impetus for weight regain.’, American Journal of Regulatory, Integrative and Comparative Physiology. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3174765/.
  2. Henry, C.J. (2005) ‘Basal metabolic rate studies in humans: measurement and development of new equations’, Public Health Nutrition. Available at: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/61A9EA486ABFA478FEF2FCE1E70D5BEE/S1368980005001394a.pdf/basal_metabolic_rate_studies_in_humans_measurement_and_development_of_new_equations.pdf.
  3. Von Loeffelholz, C., Birkenfeld, A. (2019) ‘The Role of Non-Exercise Activity Thermogenesis in Human Obesity’. Available at: https://www.ncbi.nlm.nih.gov/books/NBK279077/.
  4. Westerterp, K.R. (2004) ‘Diet induced thermogenesis’, Nutrition & Metabolism. Available at: https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-1-5.
  5. Acheson, K.J. (1993) ‘Influence of autonomic nervous system on nutrient-induced thermogenesis in humans‘, Nutrition. Available at: https://chemport.cas.org/cgi-bin/sdcgi?APP=ftslink&action=reflink&origin=npg&version=1.0&coi=1%3ASTN%3A280%3ADyaK2c%252FgtlOjtw%253D%253D&md5=78b43ab7181023960980b89955219f28.

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