WHAT IS A CALORIE?
A calorie is a unit of energy.
Specifically, the amount of energy required to heat 1g of water by 1 degree celsius.
But this is essentially a pointless piece of information for much of the population (unless you’re really into pub quizzes, in which case store that nugget away somewhere in case you need it one day).
We use ‘calories’ to measure the amount of energy in items of food and can therefore calculate our own daily requirement for energy, or TDEE (Total Daily Energy Expenditure). In a 24-hour period we utilise these calories for exercise and walking around, but even sat still, or while sleeping, we will use calories to regulate our body temperature, keep our heart beating and keep breathing.
CALORIE REQUIREMENTS
NHS guidelines suggest that an average man require 2500 calories per day and an average woman requires 2000 calories per day, although with the caveat that “These values can vary depending on age, size and levels of physical activity, among other factors.” So essentially, this figure is a very rough estimate and every individual is different.
SO HOW MANY CALORIES DO I NEED?
There are two ways to determine what your daily calorie requirement should be; the first involves keeping a food log; the second is using an online calculator.
By keeping a food log for a period of time and monitoring your weight during this same period, you are able to see the effect of that calorie intake on your body. As an example, let’s take a look at ‘Dave’:
Dave keeps a food diary for 7 days and on average he consumes 2300 calories per day. During this time, his weight drops by 0.5kg. This indicates that his calorie requirement or TDEE is likely to be more than this value of 2300, but as Dave’s goal is slow, sustainable weight loss, he decides that a 0.5kg loss each week is ideal, so he continues to eat 2300 calories per day. If he wanted to gain weight, he could increase this number by 100-200 calories per day and see what effect eating 2500 calories per day has on his weight. He could then continue to monitor his weight and alter his calorie intake depending on how his weight was changing.
For those who want a ball park figure for their calorie intake to aim for without having to keep a food log, there are a number of TDEE calculators available online (there's one on my homepage here that does a good job: https://eatonperformance.wixsite.com/eatonperformance). These calculators use your age, height, weight and activity levels to calculate a ball park figure for your TDEE and will offer altered figures based on weight loss, maintenance and weight gain. You can then choose the value appropriate to you, eat that number of calories and monitor body weight. Depending on the success of that intake towards your goals, you can adjust your intake when necessary to keep progressing.
WHAT IS TDEE?
TDEE is your total daily energy expenditure (the amount of energy you use in a day). It is made up of BMR, NEAT, EAT and TEF (nearly as many acronyms as an episode of Line of Duty!)
-BMR - basal metabolic rate - the energy used by your body for all the chemical reactions necessary to keep you alive.
-NEAT - non-exercise activity thermogenesis - the energy required for any movement (that isn’t exercise) that you do during the day. This includes walking around, standing up, doing the housework and even small movements made while fidgeting.
-EAT - Exercise activity thermogenesis - the energy required for exercise (running, cycling, resistance training etc) - surprisingly less than you might think.
-TEF - Thermic effect of food - the energy used by your digestive system to break down and absorb your food (a small number in the grand scheme of things, but some foods require more energy than others to digest, protein in particular).
CALORIE BALANCE
Your goals will determine how you need to manipulate your calories. To maintain weight you need to eat your TDEE calories; to lose weight (most likely with the aim of this being a loss of body fat) you need to eat less than your TDEE (did someone say calorie deficit?!); to gain weight (most likely with the aim of increasing muscle mass) you need to eat more than your TDEE.
‘BURNING CALORIES’
The mistake lots of people make, is to set a calorie target based on their TDEE, and then try in some way to factor in their exercise calories. Tools such as MyFitnessPal and the health apps on Android and Apple phones are able to calculate your calories from activity and then add these to your daily target. The problem with this is that often, activity trackers greatly overestimate the calories burned during activity, so you will find that they are adding too many calories to your daily intake, which if you then consume, will affect your goals. The way to overcome this, is to ignore your activity output on any given day, but factor it into your TDEE to create an overall weekly calorie deficit.
CREATING A CALORIE DEFICIT
If we take a closer look at fat loss, it is necessary to create a calorie deficit. Where most people go wrong with this, is in trying to create that deficit through exercise. Your 60-minute session at the gym, or a 5k run in the morning before work, or that legs, bums and tums class in the evening burns surprisingly few calories. It’s much more effective to look at your activity levels as a whole for a typical week (not what you would ideally do, but what you actually do - that way if you have a particularly good week, it a bonus!). Then use your activity level to set a calorie target. You can then either eat this calorie target every day, or multiply it by 7, to get your target for the week and as long as you hit this number overall, you can eat slightly more on some days than others, depending on what’s going on in your life that week, or to fit take around training and non-training days, but this isn’t essential, it’s a matter of preference.
SUMMARY
Progress towards your body composition goals are determined by your overall energy balance (energy in vs energy out)
If you eat more than you use, you will gain weight; if you eat less than you use, you will lose weight.
To estimate your calorie requirement, use a TDEE calculator and input your age, weight, height and typical activity levels for the week.
Some calculators will then give you a value for weight loss, maintenance and weight gain; but if not, multiply your TDEE by 0.8 for weight loss, 1 for maintenance and 1.2 for weight gain.
Monitor the effect of your chosen calorie intake on your body weight and modify the target up or down depending on progress.
Aim for around 0.5kg weight loss per week (less if you only have a small amount to lose, but this can be more if you have a lot to lose) or less than 0.5kg weight gain (to minimise fat gain).