Understanding calories by Nourish

In short calories are a unit of energy, which is a quantifiable value we can use to measure the energy contents of food in terms of what it can contribute in the form of fuel, to the body (?Did you know, a calorie is the amount of energy required to heat one litre of water by one degree?). When we pair this information with what we know about the body and how it both uses calories and food, we then have some valuable knowledge with which to work out a plan to create a calorie deficit, which in turn will lead to the body releasing fat store and overall body fat levels coming down.

So now we have laid out what really matters when it comes to fat loss, let’s have some science about how the body deals with energy and what influences the storage of said energy in to fat.

"Creating fat loss really is as simple as building a solid base with calories, and then using this to calculate a suitable macronutrient intake” - Dr Paul Rimmer

When you have an excess of something, it has to go somewhere. When this happens with calories, from any source of food, if they are not burned off then they have to be stored. The body has different pathways for the different nutrients; Fat, Carbohydrate and Protein.

So how do we decide what define a calorie requirement for an individual? The government tells us on the side of our cereal box that the Recommended Daily Allowance (RDA) is 2000Kcals for women and 2500Kcals for men. But does this mean a 7ft man needs the same as a 5ft man? Or that a 6ft woman needs less than a 6ft man?

No, it tells us very little about ourselves. These are just completely average guidelines which will approximately fit the middle ground of the population.

What we first need to understand is what our calorie output is so our nutritionist or dietitian can manipulate the content of our diet to create a deficit suitable for sustained weight loss. This requires understanding the two following values:

Basal Metabolic Rate (BMR)

What this refers to is the amount of energy required to run your bodily functions for 24 hrs. The cost of keeping your brain on, your heart beating, your lungs moving etc. It includes no movement. Imagine you were to lie completely still in bed for 24 hrs, your BMR is how many calories you would use in that period.

There are factors that alter your bmr; height, weight, age, gender and body composition. It is important to understand that the calculation to approximate your BMR becomes less accurate at extremes of the scales. This is where nutrition professionals, such as those at Nourish, can help to make the figures as accurate as possible.

In the UK we have adopted the Oxford Henry calculation for calculating BMR, but there are others such as the Schofield equation, and in America the Harris-Benedict formula. The American equation is very out-dated, but for some reason has been adopted by the fitness industry in the UK, so be wary if your Personal Trainer calculates your calorie requirement, or at least ask what calculation he uses.

There are ways of calculating calorie expenditure very accurately, such as doubly labelled water and Douglas Bag calorimetry, but these require lab conditions and trained professionals to carry out. Best to just stick with the calculator for now.

So now we have a figure to start off with, but not the full picture, what now?

Physical Activity Level (PAL)

BMR is difficult to modify, the easiest way to change it is to alter body composition and this process can take a long time.

Your physical activity level is not just related to how much exercise you do, although this is a big modifier, but also the nature of your day to day activities. For example if you work on a construction site, your job is going to be more physically demanding than that of an office worker. We will cover easy ways to add in more physical activity to your day other than the gym in another chapter, but there are quick fixes to bump your PAL level up.

PAL works in unison with BMR as a multiplication factor. For example if you are inactive at work and sedentary in your free time, your PAL would be 1.2 x BMR. At the other end, if you worked a physical job and did heavy exercise, it would be 1.9 x BMR.

So clearly this is a the best way to increase your energy expenditure, and as the aim of losing weight is to create a calorie deficit, exercise can help over diet alone. Although there is an adage in the industry; ‘You can’t out train a bad diet’.

So we’ve touched on how we figure out our calorie requirement, how do this then convert over to a weight loss diet? On the surface, its simple. Find out how many calories you need, and subtract 300-400, and eat those many. But dig a little deeper and it becomes clear it is far more nuanced than that. For starters, if the foods you are eating aren’t of the right nutrient profile, or arent satisfying enough, the body will begin to suffer, and the diet will begin to fail due to hunger, low energy levels and cravings. This is where old habits may re surface, or workouts may be skipped.

Ensuring this doesn’t happen requires macronutrient breakdown to be pre planned, meal timing to be appropriate and the types of food being consumed also come into play. But we will go into that later.


There are two varieties of nutrients, macro and micro. Simply put, you can see macro nutrients, you can’t see micronutrients. Macro-nutrients are comprised of 3 different forms, Fat, Carbohydrate (CHO) and Protein. Some will include alcohol in this list as it contains calories, but as it has no nutritional value, labelling it a ‘nutrient’ is misleading.

Whole books have been written around this subject, so we shall just have a whistle stop tour of each of the three here.


At 9 calories per gram, fat is the most energy dense of all the macronutrients. Calling it fat gives it a negative connotation, and in many ways this is understandable. Although there are different forms of fat, it has the closest similarity to what may be around your waist. But as we discussed with calories, it is excess that causes weight gain. Due to its nutritional density, it can cause the biggest fluctuation in caloric intake with the least amount of change in intake volume so probably needs to be monitored a little more closely.

Fat will always have a place in a healthy diet. It can be used as an energy source, it helps us with absorption of vitamins and minerals, it is the building block for a lot of hormones and it keeps our hair, nails and skin healthy.


Carbohydrate is the fuel of choice for our body and provides 3.5 kcal per gram, usually rounded to 4.. We will turn all carbohydrates in to the body's preferred energy currency; Glucose. The type of carbohydrate will determine how quickly it is converted to glucose, this is known as the Glycaemic index (GI). Low GI carbs are complex, and take longer to break down to glucose, this is beneficial as it gives a sustained and controlled energy release. Wholegrains, Brown Bread, and Oats are examples of low GI carbs. Just think, the browner the better.

High GI carbs will give a ‘spike’ to the glucose in the bloodstream, which initially is a good feeling, but is often followed by a crash, and this can triggered a cycle of craving for a sweet fix, however this should only really be a concern and something to watch out for if you're eating this foods on their own and they are making up a large portion of your total daily calorie intake.

There are places for all types of carbs in the diet, but at a basic level, it is better to go for the Low GI options as much as possible. It is worth noting that high GI carb sources can often come with a high fat content, such as chocolate, cakes and doughnuts.

You may have been hearing carbs being the worse thing for gaining weight, but as is important to stress, it is not the food type, it is the excess. Cutting out carbs is something that is becoming increasingly common, and is often labelled as ‘Ketogenic’. Takes a short memory to forget that cutting carbs is the premise for the Atkins diet, which was show to not only be ineffective, but also not actually that healthy due to the amount of fat and protein being consumed.

More important that focusing solely on the volume of carbs you eat, is to focus on the source and the timing. Eating carbs around workouts is a good way to energise pre gym, then re fill muscle energy stores afterwards. Carbs are not the enemy!


Protein, at 4kcal per gram, is usually considered the nutrient to care about the most when it comes to losing weight or in an exercise programme, and for good reason. Protein is the building blocks for Amino Acids, which are involved in pretty much every chemical process in your body so having a good amount is important. It also helps muscle repair after damage which is why its good to consume if you are exercising.

When dieting protein is a useful tool as it increases satiety (the feeling of fullness) more effectively than the other 2 nutrients. This means a diet high in protein will help you to feel satisfied even when you are on a calorie deficit diet. Animal protein sources often are also high in fat, so going for lean cuts of meat is important to avoid over consuming calories due to fat content

So there you have it, a whistle stop tour of the three macronutrients, all of which play a role in your diet and none of which should be avoided. What becomes important is ensuring these macros are calorie adjusted and calculated to make sure you are getting the right balance of foods and consuming the right amount of calories to create a deficit and aid weight loss.

Creating a diet plan is difficult, and requires good knowledge of food and appropriate macro breakdown for the task in hand.  But that’s what you have Nutritionists and Dietitians for. They can look at the amount of calories you need for maintenance, then adjust the numbers, and create a diet plan to allow you to reach your goals.

Written by Joseph Parker and David Stache