What is Nutrition Part 1: Calories, what ARE they?

Nutrition, according to the World Health Organisation, is defined as "the intake of food, considered in relation to the body's dietary needs. Good nutrition – an adequate, well balanced diet combined with regular physical activity – is a cornerstone of good health"(1).

What does nutrition mean and why is it important?

Nutrition is, in essence, the word we use to describe the food and drink that we consume, in terms of the nutrients therein, and the effects which we wish it to have on our body and mind. Nutrition is the single most important factor in optimising your performance in boot camp and the health or body composition changes you wish to see in yourself.

By managing our nutrition, what we eat and drink, we can therefore manage how we feel, how we perform in training or competition situations, and what we look like as a result of what we do (after all, we all want to look good naked, right?).

Nutrition can directly change your risk of disease, ailment, age-related ill health and performance in mental or physical tasks, this means that getting it right should be considered paramount. Nutrition is literally the cornerstone to everything that you do, it’s the fuel that charges your brain, your body… just everything!

Of course, that’s all well and good, but how do we look at nutrition, and how do we know we are on the right track?

Those are the two questions I want to answer in this series of articles. By the end of it you should be in a great place to read the rest of the content on this site as you’ll have a solid background understanding of what we are talking about.

Firstly, how should you start to look at your nutrition?

Whilst this article will help you a lot and I urge you to read it, those of you who are taking the first steps on your fitness and health journey should check out Nutrition Advice for Beginners first. This will educate you on getting a handle on your own nutrition, and starting to improve your health and results straight away.

Nutrition should be viewed in a hierarchy of importance. The subject itself can be very complex and confusing, and a lot of information is available to us which is either misleading or simply not useful, meaning that figuring out what is relevant can be a real headache. For this, I like to use the following diagram originally suggested by Eric Helms, of 3DMJ fitness coaching, which shows us the order we should look at things when trying to optimise performance in training or exercise and body composition*:

*More on this in a moment.

Nutrition Piorities | British Military Fitness

Let’s look at each level in turn, explaining what they mean, how to know you are on the right track, and why they appear where they do on the hierarchy.


Calories are a unit of measure for energy, like Kilowatt hours which appear on your electricity bill. The term ‘calories’ when used to talk about food is actually incorrect, as the unit of measure we use to measure food energy is kilocalories, shortened to ‘kcal’ on food packages, which is actually 1000 calories. We use the two terms interchangeably when talking, and I will do so here, but for the sake of completeness I wanted to include this little disclaimer.

1kcal is equal to around 4000 joules (4186.8 to be exact) and is the amount of energy needed to raise the temperature of a litre of water by 1 degree Celsius. The human body requires calories to live, breathe, walk around, run, jump, speak, play Twister and read fitness articles. Without energy, our body will very quickly shut down.

Because calories are found in the food and drink that we consume, almost entirely (unless you are on a glucose drip for example) it’s important to consume the correct amount of food for your goals, which is dependent on your body and genetics.

Without eating sufficient calories your performance in boot camp will be directly impaired, meaning that your fitness progress will eventually stagnate or even regress; but more than this your body will not have enough energy to allow you to do other daily things. Your brain will run more slowly which makes it hard to focus at work or study, you will feel lethargic and ‘bogged down’ with heavy legs when walking around, and you might find it difficult to stay awake for a full day. A final issue with dramatically under eating is that hormonal functions will start to take a dive which will effect your mood, your body composition and even your libido.

Overeating on the other hand, even if the foods you consume are of the ‘healthy’ kind, will eventually make you fat. No ifs, ands or buts.

So...how many calories do we need?

There are a number of different calorie calculators which can be found online which will use a few different formulas to work out an estimate of your calorie needs. Click here for the one I personally use when starting with a new client.

Use this to work out your needs both on days you don’t do BMF / Bootcamp, and days you do. Bootcamp will be both intense and moderate exercise, so to play it safe I’d add this time to the moderate block

Eating this many calories on the requisite days should allow you to maintain your current weight; try it for 2-3 weeks and see what happens. It will almost certainly be too high or low (estimates always are) so remember this and ALWAYS adjust what you are doing depending on real-world results.

Once you have found the rough amount of calories needed to maintain your weight, add or subtract 5-10% of your total amount of daily calories to gain or lose weight. So if you are eating 2500 Kcal and you are maintaining your weight, but wanted to lose weight, subtract another 5% of those calories, so you then eat 2375 for a week, and see if that makes you lose weight. If not drop it again another 5% until you start getting a consistent weight loss of 1-2lbs per week.

Now onto Nutrition Part 2, where we discuss where these calories come from, and the different things that foods do for us….


References for the ‘What is Nutrition?’ series.

  • (1)    www.who.int/topics/nutrition/en/
  • (2)    Helms et al. (2014). ‘’Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation’’. JISSN
  • (3)    http://examine.com/supplements/Fish+Oil
  • (4)    Aragon and Schoenfeld. (2013). ‘’Nutrient timing revisited: is there a post-exercise anabolic window?’’ JISSN
  • (5)    Norton et al. (2012) ‘’ Leucine content of dietary proteins is a determinant of postprandial skeletal muscle protein synthesis in adult rats’’. US National Library of Medicine



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