How Your Body Utilises Energy and The Role it Plays in Fat Loss and Gain

In this article we are going to look at energy balance and how it dictates whether we gain, lose or maintain our weight.

What is Energy Balance?

So, what is energy balance?  Well it is the relationship between what we consume through food and drink vs the energy that we use each day.  Calories are the units that we use to measure this.

This energy equation is governed by the first law of thermodynamics and this is the science behind how our weight drops, increases or stays the same.

As you will learn, this balance is affected by a number of things unique to each individual and as such is very complex.  Therefore, the NHS recommended guidelines of 2500 cals per day for a man and 2000 for a woman are not really that useful as they are based on averages; a person’s particular goals, intake and daily activity MUST be taken into account when estimating daily requirements.  Interestingly, the number of calories required by people in Western society is steadily increasing which is no surprise in light of the obesity epidemic and the ever-growing availability of highly processed, calorific foods.

Going back to thermodynamics then, this law states that energy cannot be created nor destroyed, it is continuously reused.  The calories we consume must therefore be used as work, lost through heat or stored and this is a continuous, dynamic process.

How Do We Burn Energy?

The amount of energy that we burn and therefore require can broadly be broken down in to four stages.

  1. BMR
  2. NEAT
  3. TEF
  4. EE

BMR is our Basal Metabolic Rate.  This is the minimum energy required to keep your body functioning at rest.

NEAT is our Non-Exercise Activity Thermogenesis.  This is the energy we expend doing everything except eating, sleeping and exercising.  It includes things like fidgeting, everyday tasks etc.

TEF describes the Thermic Effect of Food.  This is the energy required to break down the food that we consume; protein had the highest thermic effect.

EE is our Energy Expenditure so any energy required to perform exercise.

These all make up out Total Daily Energy Expenditure (TDEE).  When we are eating the same as our TDEE, we are in an energy balance which means we will maintain our weight.

Why Is Energy  Balance Important? 

Whilst understanding energy balance is key when it comes to weight loss, it also has a huge impact on vital bodily functions.  When you are in a negative or positive balance, i.e. eating too much or too little, everything from your metabolism to your moods can be affected.  This is because our bodies are happiest when they are in homeostasis, a stable balanced state, so they will constantly strive to achieve this.  This is why people often find it difficult to consistently lose and/or gain weight.

Creating a Calorie Deficit 

To be in a negative energy balance you must eat fewer calories than you require which puts you in a deficit.  This is necessary for fat to be lost.

Severe deficits can, however, lead to a reduced metabolism, decrease in bone mass, imbalanced hormones, reduced concentration, feelings of cold and agitation.  It can also reduce your NEAT and EE.

Your body will literally slow down to reserve energy for vital functions which can leave you feeling pretty rubbish!

Calorie Surplus

On the other extreme we can be in a positive energy balance which means that we are eating surplus calories required for our daily needs.  This can be important to someone who wants to gain muscle and will inevitably lead to weight gain.

If excess calories are consumed without strength-based training, however, it can create excess fat stores which may lead to higher blood pressure, increased cholesterol and our risk of diseases such as diabetes and some cancers increases.

The amount we eat and the amount we move can therefore have a huge impact on our overall health and wellbeing.

Creating Stability

As mentioned, our bodies like balance and we are therefore extremely adaptable.  As we lose weight, our bodies will adjust to the fewer calories and vice versa.  We will basically end up as either smaller or larger versions of our previous selves and the number of daily calories we require will change accordingly.  Therefore, if you are dieting and losing weight, the calorie deficit you created at the beginning will not serve you for long and will likely become your maintenance calories.  This means you will either have to eat less than you previously did to maintain your weight or you will need to exercise more.

The same works vice versa, if you gain weight then your maintenance calories will increase so you will have to create a larger deficit than you may have previously to lose weight.

Is it all down to calories?

Whilst weight gain and loss fundamentally come down to the number of calories consumed, this cannot and should not be viewed in isolation.  Our lifestyle and environment play a major factor in whether we achieve energy balance or not.  Whilst we all have the best intentions, we are constantly tempted by high calorie, processed food and our brains are programmed to seek out the foods that will give us the most energy in any given moment.  In addition to this, people are required to move less and less in modern society yet are often stressed so don’t feel like exercising which plays an important factor in our calorie expenditure.


Whilst the simple law of thermodynamics cannot be broken, it is clear that energy balance is a very complex and dynamic process.  The goal posts are constantly moving and external factors play a key role.  For this reason, it is not an exact science so you will have to experiment to find what works for you.  Whatever you are trying to achieve, increasing activity levels through more activity and/or strength based exercise can help the process and help you maintain your ideal body composition.  But remember, you don’t have to live this way forever.  Once you have achieved your goal you can remain in an energy balance through excellent nutrition and an active lifestyle.

This was brought to you by Rebecca Flannery, Evidence Based Nutritionist at Transformational Nutrition.