most calorie tracking apps have you put in a few qualities about yourself (gender, age, weight, height, blah blah) and spit out some number that is supposed to be your calorie goal. nothing wrong with that! but if you’re curious as to where the magic number comes from or want to feel more involved in your lifestyle decision making, the process is actually quite simple to do by hand.
a bunch of words & what they mean
BMR (Basal Metabolic Rate): aka Resting Metabolic Rate (RMR), this is the number of calories your body needs per day to keep up with essential life functions like breathing and keeping your heart breathing (among others). these calories make up the largest chunk of what you burn in a day, but don’t account for anything you do that is not strictly keeping you alive.
TDEE (Total Daily Energy Expenditure): this is an estimate of the total number of calories you burn in a day. it includes the automatic bodily processes that BMR reflects, but it also captures calories burned in minor movement, talking, walking, and exercise.
Calorie Deficit/ Surplus: a deficit is when you are burning more than you consume, while a surplus is where you are consuming more than you burn. in a deficit, you will lose weight, whereas in a surplus, you will gain. what you consume (or rather, don’t consume) in your deficit/ surplus will determine which mass you will lose- body fat or muscle.
calculations
BMR: a person’s BMR is determined by a number of factors that can’t be super easily boiled down, but the most basic calculation uses your gender, age, weight, and height to ballpark it. there’s a few different equations that can make this estimate, but i will be using the Mifflin St Jeor formula:
- for men: BMR = (10 x weight [kg]) + (6.25 x height [cm]) – (5 x age [yrs]) + 5
- for women: BMR = (10 x weight [kg]) + (6.25 x height [cm]) – (5 x age [yrs]) – 161
TDEE: the TDEE equation uses your BMR and your activity level to estimate how many calories you burn total in a day. when i do this calculation, i do not include any physical activities that i would track on my watch (lifting, cardio, sports, walking for exercise, etc) since i add those calories burned to my total independent of my TDEE. if you don’t have your activities importing to your tracker, then you should account for your daily exercise in your TDEE calculation.
- TDEE = BMR x (activity factor)
| Activity Level | Description | Activity Factor |
|---|---|---|
| Sedentary | Desk job and little or no exercise | 1.2 |
| Slightly active | Exercise 1-3 times a week | 1.375 |
| Moderately active | Exercise 3-5 times a week | 1.55 |
| Very active | Exercise 6-7 times a week | 1.725 |
| Extremely active | Physical job or regular training | 1.9 |
Deficit/ Surplus value: generally speaking, 3500 calories roughly translates to 1 lb of body mass. so if your goal is to lose 1 lb/ week, then you would aim for a deficit of 500 calories per day (3500 cals/ 7 days). if you have a low TDEE, then this can be a challenge as you do not want to eat less than what your body needs to perform essential functions (your BMR). but any deficit is a deficit- progress might be slower, but you will lose weight if you are consuming less than you burn. your weekly weight loss goal largely depends on the state of your body (if you are a little guy like me, 1 lb is a larger % of my total body mass as opposed to a larger fellow like andward), but generally speaking 2 lbs/week is the maximum for safe weight loss.
- daily deficit/ surplus = (weekly weight loss/gain goal in lbs) x 3500 cals / 7 days
and if its not already obvious, if you are simply looking to maintain weight, then your value will be 0 and your calorie goal should be your TDEE.
exhibit a: yours truly
- i did at the body scan at el gimnasio which uses a different equation involving body fat %, and it said i have a BMR of 1369 kcals
- using the calculation above: (10 x 58.967 kg) + (6.25 x 157.48 cm) – (5 x 24 yrs) – 161 = 1293 kcals so pretty close!
- using a factor of 1.2x (since my job is incredibly sedentary), i calculated my TDEE w/o exercise to be 1643 kcals
- i settled on a deficit of ~100 kcals, since i’m not looking for drastic changes and anything more than that only allows me to eat a blade of grass per day anyways
aaaaand thats how i came to 1550 as my baseline daily calorie goal!!
as i mentioned earlier, i add calories burned in my workouts to my total for the day as well. between lifting, cardio, and some sport or another, i typically burn 500-600 calories per day and end up eating a bit over 2000 calories. if i included exercise in my TDEE, i would use a factor of 1.55 to get a TDEE of 2122 which i could use to come pretty close to the goal i had above.
in summary
i haven’t typed an informative paper since high school, so i hope this made sense! i learned most of this just by googling bc i find bodies suuuppeer interesting, but you can use websites like TDEE calculator or calorie tracking apps like myfitnesspal to find your BMR, TDEE, come up with your own calorie goals, and learn more!
something else to keep in mind- since these calculations are based on data from your body at the present, your BMR and TDEE will change over time. if you are losing weight, what was once a deficit might not be a deficit anymore. the inverse is also true: if you are looking to bulk up, a calorie surplus will no longer be as much of a surplus since those calories are now also being burned to maintain your new mass.
these calculations are also not an exact science- there are still some parts of the process that only the body knows and that are a mystery that can’t be represented by some formula. the only way to truly know how well your cut or bulk is going is by keeping track of your progress. whether that’s visual like taking a gander in the mirror or taking progress pics, or it’s more data-based like tracking body weight, calories consumed, and calories burned to find a more straightforward correlation. just try not to take it too seriously- its a fun little game to know what your body is doing without telling you, but all of this can be a slippery slope if you let it go too far.
ok brain dump over byeeeeee 🙂
what kate ate 
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