Calories – What Are They?


caloriesShould I try the latest fad diet is a question that people ask themselves and PT’s often while others want to know how to lose fat through better eating habits. Now the interesting thing is that despite the rather broad range of topics, the main topical area always comes round to: CALORIES.   Why? Because people seem to be forgetting the role that calories play in weight management!  With all the “creative” diets that have come up in the last decade (i.e. “if you eat certain foods, or certain combinations of foods, then you can eat as much as you want and still lose weight) people seem to be getting confused about what really matters. So hopefully the following will help clear up any confusion.

To the intermediate fitness enthusiasts – this post will likely be a refresher. But read on! Sometimes it’s helpful to go back to the basics in order to avoid getting swept away by the latest fads and diets!

To the less advanced fitness enthusiasts – the information in this post is CRITICAL to your success! I’m continuously shocked by how many people spend hours at the gym but don’t have any idea how much they should be eating. If you want to achieve consistent fat loss results, you MUST know your calorie requirements!

So let’s start at the beginning.

 Calories – What Are they?

(Ignore the voice in your head that says “calories are those evil buggers that make me fat”.)

By definition, a calorie is the amount of energy required to raise the temperature of 1g of water by 1 degree Celsius. Since that definition likely does nothing for you, let’s simplify things and say that a calorie is simply a measure of energy.

The word “calorie” is used to describe 2 things:

The amount of energy in food

The amount of energy that is stored in the body as body fat and glycogen (stored carbohydrates) the number of calories in a food is just a measure of how much potential energy that food contains. Here is the breakdown:

1g of carbohydrate = 4 calories

1g of protein = 4 calories

1g of fat = 9 calories

As human beings, we require energy to perform basic bodily functions such as breathing, circulating blood, digesting food, and regulating hormones. The amount of energy required to perform these basic bodily functions is known as your Basal Metabolic Rate (BMR). Of course, we also require energy to fuel daily activities such as walking to work, shopping for shoes, and working out at the gym. The greater the intensity of our activities, the more energy we require.

Pretty obvious stuff, I know.

So let’s move on to the MOTHER of all nutrition laws: The Law of Energy Balance. While simple and straightforward, this Law answers most of the weight loss questions out there!


The Law of Energy Balance states that:

If you burn more calories than you consume, your body must tap into stored fat for energy to make up the calorie deficit

RESULT: You will lose weight

If you consume more calories than you burn, your body will store the surplus calories

RESULT: You will gain weight

No fancy diets, no “must-eat” foods, no “off limit” items. Let me say it once again just for fun: If you eat more than you burn, you will gain weight!

Now a couple of additional statements…

Too much of ANY food will get stored as body fat. It doesn’t matter whether you’re eating too much chicken or too many Doritos, at the end of the day if you’re consuming more calories than you burn, you WILL gain weight.  Usually this weight is in form of body fat. Now I say “usually” because as many of you weight-lifters know, muscle growth requires the body to have excess calories at its disposal.   When you overload your muscles with work, your body directs your calorie surplus to building more muscle.   However, if the surplus of calories you have in your body goes beyond what you need to build and repair muscle, then those extra calories will be stored as body fat.

The opposite is true as well. If you are burning more calories than you consume each day, your body won’t store what you eat as body fat EVEN IF what you’re eating is “junk food”. Now don’t get me wrong, nutrition is a vital part of health and wellness, and it’s true that some foods may get stored as fat more easily than others because of the way they affect your hormones. So don’t go stuffing your face with 10 snickers bars a day! All I’m saying is that calories are THE most important factor in any fat loss program. Strive to make the healthiest food choices possible. Eat fruit instead of candy. Eat salad instead of a bagel. But also be kind to yourself and don’t freak out when you eat a little bit of junk food. At the end of the day, as long as you burn more than you eat, your body will forgive you.

So now that we’ve cleared up the concept of energy balance, the next thing you need to know is how many calories you should be consuming each day. After all, if you don’t know what your body’s daily caloric requirements are, how are you supposed to know if you’re eating more or less than you should be each day? If you don’t know what your target is, how are you supposed to know if you deserve a gold star on Monday but need to scale back on Thursday to compensate for overdoing the calories on Wednesday? Without knowing what your caloric requirements are, you’re essentially shooting in the dark!

So let’s get down to the mathematics of calculating your caloric requirements.

The Harris-Benedict Equation is a formula that uses your BMR and activity levels to determine your Total Daily Energy Expenditure (TDEE). Your TDEE is critical to know, as it establishes the total number of calories your body burns in 24 hours. This establishes your “maintenance point” – the point at which you’re not gaining or losing any weight because your calorie intake is equal to the number of calories you burn. The Harris-Benedict equation is accurate because it uses factors such as age, height, weight, and sex to determine your Basal Metabolic Rate (BMR). The only factor omitted is lean body mass. As you know, leaner bodies require more calories to maintain their muscle mass. So for the very muscular, the Harris-Benedict equation will underestimate the calories required to maintain body weight. For the very fat, it will overestimate the calories required to maintain body weight.


Here is the formula:

Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) – (6.8 X age in years)

Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) – (4.7 X age in years)

Note: 1 inch = 2.54 cms ; 1 kg = 2.2 lbs

Let’s take the example of a 30 year old male who is 5’10’’ weighs 180 lbs, and plays sports 3 times a week. Let’s name him Bob.

BMR    = 66 + (13.7 x 81.8) + (5 x 177.8) – (6.8 x 30) = 1871.66 calories

As you can see, Bob requires 1872 calories just to perform his basic bodily functions.


Now we need to take into consideration how much additional activity he’s doing in order to establish his TDEE. To calculate this, we simply multiply his BMR by a pre-established “activity factor”:


Sedentary [little or no exercise / desk job] = BMR X 1.2   Lightly active [light exercise / sports 1 – 3 days per week] = BMR X 1.375   Moderate active [moderate exercise / sports 3 – 5 days per week] = BMR X 1.55    Very active [hard exercise / sports 6 – 7 days per week] = BMR X 1.725   Extremely Active [intense daily exercise / physical job and sports / 2x training] = BMR x 1.9    After taking Bob’s activity factor into consideration, we can see that he requires 2573 calories to simply maintain his current body weight.

Now that we know how to calculate your maintenance levels, the next step is to simply adjust your calories depending on what his goals are. If you want keep your weight the same, you must ensure that your intake is exactly at your maintenance level. If you want to lose weight, you must create a deficit by either consuming fewer calories or burning more calories through exercise. To gain weight, you must increase your calories above your maintenance level (and engage in some serious weight training to avoid gaining body fat)!

 Calories – How to Cut them to lose weight

So how do you cut calories in order to lose weight “the right way”?

Well, one pound of fat carries 3500 calories. So, if you want to lose a pound a week, you simply need to create a 3500-calorie deficit through diet, exercise, or both! Similarly if you want to lose 2 pounds a week, you simply need to create a 7000 calorie deficit. But let me interject with a word strong WORD OF CAUTION!   If you create too large of a deficit your body will pick up on the fact that you’re starving yourself and will respond by slowing down your metabolism.

So don’t go consuming 500 calories a day with the assumption that you’ll lose half a pound each day. Your body is smart and it will catch on quicker than you think! The safest approach is to reduce your calories by 15 – 20% below your maintenance level.  Reducing your calories by 30% may also work well for some, so feel free to experiment week to week. Just remember, the larger the deficit, the sooner your body will catch on and start slowing down your metabolism!


 My Recommendation:

Use the Harris-Benedict Equation to determine your maintenance levels (TDEE) Commit to eating 15 – 20% fewer calories than your maintenance level each day Track your progress week to week and adjust your intake and exercise to either slow down or accelerate your progress.

Whether we like it or not, weight loss really is a numbers game! In order to succeed, you need to be precise about how much fuel your body requires. Give it too much? It’ll be stored as body fat. Fail to give it enough? It’ll start to shut down. There’s no magic pill, but there’s certainly a mathematical formula that can help solve the fat-loss mystery!



Call 0141 639 6648 to book a session
Caroline Brown

Caroline Brown

Personal Trainer & Owner at C & Believe Fitness
Exercising to me is a way of life, At C & Believe Fitness you will Feel Better within yourself, you will Feel Healthier and you will Feel Fitter. Call 0141 639 6648 / 07971 698 390 today or Email me at for a FREE evaluation of your fitness needs and goals.
Caroline Brown
Caroline Brown
Caroline Brown
Caroline Brown

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