Everything you eat and drink contains some energy and sum of these energies is your energy intake. It is measured in kilojoules (kJ) or kilocalories (kcal). This energy intake, or how much you can eat, is the most important aspect to consider if you want to lose, gain or just maintain your current weight.
Everybody is different and has different energy needs. For example, if you have a physically demanding job or do a lot of sport you can eat more without gaining weight as opposed to your friend who sits all day in front of a computer screen. If you struggle with your diet you can use this guide to learn how to calculate calorie intake to optimize it.
BMR – Basal Metabolic Rate
The first thing we need to determine is your basal metabolic rate. Simply put this is the amount of energy your body needs to maintain your weight while powering only the vital functions of your body (brain, heart, lungs etc.). This value will be the base of our calculations.
To calculate the BMR we can use these two formulas:
Men (in lbs): BMR = 88 + (6.1 x your weight) + (12.2 x your height in inches) – (5.7 x your age)
Women (in lbs): BMR = 448 + (4.2 x your weight) + (7.9 x your height in inches) – (4.3 x your age)
Men (in kg): BMR = 88 + (13.4 x your weight) + (4.8 x your height in cm) – (5.7 x your age)
Women (in kg): BMR = 448 + (9.2 x your weight) + (3.1 x your height in cm) – (4.3 x your age)
Men and women (lbs): BMR = 370 + (9.8 x lean mass weight)
Men and women (kg): BMR = 370 + (21.6 x lean mass weight)
Katch-McArdle formula is more accurate but you need to have a good estimate of your body fat. I plan to write an article about that but until then you can use this simple calculator. It uses the U.S. Navy formula for estimating body fat percentage.
My actual measurements are: weight = 137 lbs (62,1 kg), height = 63.5 inches (161 cm), age = 32
BMR according to Harris-Benedict (lbs) = 88 + (6.1 x 137) + (12.2 x 63.5) – (5.7 x 32) = 1516 kcal
BMR according to Harris-Benedict (kg) = 88 + (13.4 x 62.1) + (4.8 x 161) – (5.7 x 32) = 1510 kcal
body fat = around 15%
lean mass = 137 * (1 – 0.15) = 116.45 lbs (52.8 kg)
BMR according to Katch-McArdle (lbs) = 370 + (9.8 x 116.45) = 1511 kcal
BMR according to Katch-McArdle (kg) = 370 + (21.6 x 52.8) = 1510 kcal
In this case the difference between Harris-Benedict and Katch-McArdle is negligible but when I estimated my BMR at the beginning of my get fit journey, the difference was 150 kcal (1750 vs 1600).
The difference was this big because I was very fat and Harris-Benedict formula calculates with your weight which also includes fat. So it overestimates you energy requirements if you carry a lot of fat, as I did.
TDEE – How To Calculate Calorie Intake To Maintain Weight
TDEE stands for Total Daily Energy Expenditure. To estimate it, we need to combine your BMR with your physical activity level like exercise or just moving around. To quantify this activity we will use the physical activity multiplier:
BMR x 1.2 – for sedentary individual
BMR x 1.375 – for lightly active individual (sports activity 2 – 3 days a week)
BMR x 1.55 – for moderately active individual (sports activity 4 – 5 days a week)
BMR x 1.725 – for very active individual (sports activity 6 – 7 days a week)
BMR x 1.9 – for extremely active individual (demanding physical job and sports activity)
Since I’m sedentary for the whole week (in work, on train etc.), except three days when I train, I’m using the multiplier for a lightly active individual:
TDEE = BMR x 1.375 = 1511 x 1.375 = 2077 kcal
So my TDEE is around 2070 kcal which means that If my goal was to maintain weight I would eat around this number of calories.
As I wrote before, it is important to remember that this is just an estimation. You would eat at this energy intake and track your weight (and other measurements) for 2 – 3 weeks and adjust the intake up (if your weight is dropping) or down (if your weight is rising).
Cut – How To Calculate Calorie Intake To Lose Weight
Now that we have estimated maintenance calories we can determine fat loss calorie intake. But first, you should decide how fast you want to lose weight. This will affect how much you will have to restrict your energy intake.
There are many good ways how to determine the ideal weight loss target and one of my favourite recommendation is from Greg Nuckols (I think he has a video about this):
body fat % / 20 = % of your bodyweight you can lose weekly without increasing danger of muscle loss
Using myself as an example – 15 % body fat, 137 lbs (62,1 kg):
15 / 20 = 0.75 %
So I can safely lose 0.75 % of my bodyweight per week, which is:
137 x (0.75 / 100) = 1 lbs / week
62,1 x (0.75 / 100) = 0.46 kg / week
Now to calculate my daily calorie intake to lose 1 lbs / week (0.46 kg / week):
suggested daily intake (lbs) = TDEE – deficit = 2077 – (1 x 500) = 1577 kcal
suggested daily intake (kg) = TDEE – deficit = 2077 – (0.46 x 1100) = 1571 kcal
If I choose to lose half of that, the calculation would look like this:
suggested daily intake (lbs) = TDEE – deficit = 2077 – (0,5 x 500) = 1827 kcal
suggested daily intake (kg) = TDEE – deficit = 2077 – (0,23 x 1100) = 1824 kcal
Note on numbers 500 and 1100
Number 500 – I want to burn one pound of fat per week and it takes approximately 3500 kcal to do it. Dividing 3500 / 7 days gives us 500 per day.
Similarly, number 1100 – Burning one kilogram of fat per week takes approximately 7700 kcal, dividing 7700 / 7 days gives us 1100 per day.
Bulk – How To Calculate Calorie Intake To Gain Weight
The first thing we need to determine, similarly to losing weight, is how fast we want to gain weight. The very important thing to consider is your training status because it is one of the factors (others are hormone levels, genetics, supplements (drugs), appropriate training, rest/sleep) determining how much muscle you can build in a given time period. I like the Alan Aragon’s take on this:
|Trainee Level||Rate of Muscle Gain|
|Beginner||1 – 1.5% body weight / month|
|Intermediate||0.5 – 1% body weight / month|
|Advanced||0.25 – 0.5% body weight / month|
These values are for men, women should expect about half of this.
The calculation will be very similar to cut. Let’s say I’m a beginner and because I am a small guy I will use the low end of the range:
1% of 137 lbs (62.1 kg) = 1.37 lbs (0.62 kg)
To calculate my daily calorie intake to gain 1.37 lbs/month (0.46 kg/month):
suggested daily intake (lbs) = TDEE + surplus = 2077 + (1.37 x 200) = 2351 kcal
suggested daily intake (kg) = TDEE + surplus = 2077 + (0.62 x 440) = 2350 kcal
To explain the numbers 200 and 440
- it is realistic to expect that half of the predicted weight gain is muscle and half fat which means that if we plan to gain 1 lb of muscle we will also gain 1 lb of fat -> bodyweight gain 2 lbs/month
- to burn or store 1 lb (1 kg) of fat we need 3500 (7700) kcal
- to build 1 lb (1 kg) of muscle we need 2500 (5500) kcal
Surplus to gain 1 lbs = (1 x 3500) + (1 x 2500) = 6000 kcal / month which is approximately 200 kcal / day
Similarly to gain 1 kg = (1 x 7700) + (1 x 5500) = 13200 kcal / month which is approximately 440 kcal / day
Adjustments – When Things Don’t Go As Planned
The key to knowing when to adjust is good tracking. In the simplest form, this means to weigh every morning after toilet and before eating or drinking anything.
After a week of daily weigh-ins you would calculate the average weight for the week = (sum of all weights) / 7. After three to four weeks of tracking, you will see if you are losing/gaining weight as predicted. If not you need to make adjustments.
When you are cutting:
- if you lose weight slower than predicted -> decrease caloric intake
- if you lose weight faster than predicted -> increase caloric intake
- recommended increase/decrease is 5 – 10 % of daily caloric intake
- example: my caloric intake is 1600 kcal -> 5% = 80 kcal, 10% = 160 -> I would use 100 kcal
When you are bulking:
- if you gain weight slower than predicted -> increase caloric intake
- if you gain weight faster than predicted -> decrease caloric intake
- recommended increase/decrease is 3 – 6 % of daily caloric intake
- example: my caloric intake is 2350 kcal -> 3% = 70 kcal, 6% = 140 -> I would use 100 kcal
Now that we have calculated our caloric intake, we need to determine our macro breakdown.
I hope you find this guide helpful. If you have any questions, suggestions or experience of your own please feel free to leave a comment:)