Calorie
Calculators
Author: Tom Venuto
Date: Mar 01, 2000
Publisher: Fitness Renaissance
The first
step in designing a personal nutrition plan for yourself is
to calculate how many calories you burn in a day; your total
daily energy expenditure (TDEE). TDEE is the total number of
calories that your body expends in 24 hours, including all activities.
TDEE is also known as your "maintenance level". Knowing
your maintenance level will give you a starting reference point
from which to begin your diet. According to exercise physiologists
William McArdle and Frank Katch, the average maintenance level
for women in the United States is 2000-2100 calories per day
and the average for men is 2700-2900 per day. These are only
averages; caloric expenditure can vary widely and is much higher
for athletes or extremely active individuals. Some triathletes
and ultra-endurance athletes may require as many as 6000 calories
per day or more just to maintain their weight! Calorie requirements
may also vary among otherwise identical individuals due to differences
in inherited metabolic rates.
Methods
of determining caloric needs
There are
many different formulas you can use to determine your caloric
maintenance level by taking into account the factors of age,
sex, height, weight, lean body mass, and activity level. Any
formula that takes into account your lean body mass (LBM) will
give you the most accurate determination of your energy expenditure,
but even without LBM you can still get a reasonably close estimate.
The
"quick" method (based on total bodyweight)
A fast and
easy method to determine calorie needs is to use total current
body weight times a multiplier.
Fat loss
= 12 - 13 calories per lb. of bodyweight
Maintenance (TDEE) = 15 - 16 calories per lb. of bodyweight
Weight gain: = 18 - 19 calories per lb. of bodyweight
This is a very easy way to estimate caloric needs, but there
are obvious drawbacks to this method because it doesn't take
into account activity levels or body composition. Extremely
active individuals may require far more calories than this formula
indicates. In addition, the more lean body mass one has, the
higher the TDEE will be. Because body fatness is not accounted
for, this formula may greatly overestimate the caloric needs
if someone is extremely overfat. For example, a lightly active
50 year old woman who weighs 235 lbs. and has 34% body fat will
not lose weight on 3000 calories per day (255 X 13 as per the
"quick" formula for fat loss).
Equations
based on BMR.
A much more
accurate method for calculating TDEE is to determine basal metabolic
rate (BMR) using multiple factors, including height, weight,
age and sex, then multiply the BMR by an activity factor to
determine TDEE. BMR is the total number of calories your body
requires for normal bodily functions (excluding activity factors).
This includes keeping your heart beating, inhaling and exhaling
air, digesting food, making new blood cells, maintaining your
body temperature and every other metabolic process in your body.
In other words, your BMR is all the energy used for the basic
processes of life itself. BMR usually accounts for about two-thirds
of total daily energy expenditure. BMR may vary dramatically
from person to person depending on genetic factors. If you know
someone who claims they can eat anything they want and never
gain an ounce of fat, they have inherited a naturally high BMR.
BMR is at it's lowest when you are sleeping undisturbed and
you are not digesting anything. It is very important to note
that the higher your lean body mass is, the higher your BMR
will be. This is very significant if you want to lose body fat
because it means that the more muscle you have, the more calories
you will burn. Muscle is metabolically active tissue, and it
requires a great deal of energy just to sustain it. It is obvious
then that one way to increase your BMR is to engage in weight
training in order to increase and/or maintain lean body mass.
In this manner it could be said that weight training helps you
lose body fat, albeit indirectly.
The
Harris-Benedict formula (BMR based on total body weight)
The Harris
Benedict equation is a calorie formula using the factors of
height, weight, age, and sex to determine basal metabolic rate
(BMR). This makes it more accurate than determining calorie
needs based on total bodyweight alone. The only variable it
does not take into consideration is lean body mass. Therefore,
this equation will be very accurate in all but the extremely
muscular (will underestimate caloric needs) and the extremely
overfat (will overestimate caloric needs).
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 cm.
1 kilogram = 2.2 lbs.
Example:
You are female
You are 30 yrs old
You are 5' 6 " tall (167.6 cm)
You weigh 120 lbs. (54.5 kilos)
Your BMR = 655 + 523 + 302 - 141 = 1339 calories/day
Now that
you know your BMR, you can calculate TDEE by multiplying your
BMR by your activity multiplier from the chart below:
Activity
Multiplier
Sedentary = BMR X 1.2 (little or no exercise, desk job)
Lightly active = BMR X 1.375 (light exercise/sports 1-3 days/wk)
Mod. active = BMR X 1.55 (moderate exercise/sports 3-5 days/wk)
Very active = BMR X 1.725 (hard exercise/sports 6-7 days/wk)
Extr. active = BMR X 1.9 (hard daily exercise/sports & physical
job or 2X day training, i.e marathon, contest etc.)
Example:
Your BMR is 1339 calories per day
Your activity level is moderately active (work out 3-4 times
per week)
Your activity factor is 1.55
Your TDEE = 1.55 X 1339 = 2075 calories/day
Katch-McArdle
formula (BMR based on lean body weight)
If you have had your body composition tested and you know your
lean body mass, then you can get the most accurate BMR estimate
of all. This formula from Katch & McArdle takes into account
lean mass and therefore is more accurate than a formula based
on total body weight. The Harris Benedict equation has separate
formulas for men and women because men generally have a higher
LBM and this is factored into the men's formula. Since the Katch-McArdle
formula accounts for LBM, this single formula applies equally
to both men and women.
BMR (men and women) = 370 + (21.6 X lean mass in kg)
Example:
You are female
You weigh 120 lbs. (54.5 kilos)
Your body fat percentage is 20% (24 lbs. fat, 96 lbs. lean)
Your lean mass is 96 lbs. (43.6 kilos)
Your BMR = 370 + (21.6 X 43.6) = 1312 calories
To determine
TDEE from BMR, you simply multiply BMR by the activity multiplier:
Example:
Your BMR is 1312
Your activity level is moderately active (work out 3-4 times
per week)
Your activity factor is 1.55
Your TDEE = 1.55 X 1312 = 2033 calories
As you can see, the difference in the TDEE as determined by
both formulas is statistically insignificant (2075 calories
vs. 2033 calories) because the person we used as an example
is average in body size and body composition. The primary benefit
of factoring lean body mass into the equation is increased accuracy
when your body composition leans to either end of the spectrum
(very muscular or very obese).
Adjust
your caloric intake according to your goal
Once you
know your TDEE (maintenance level), the next step is to adjust
your calories according to your primary goal. The mathematics
of calorie balance are simple: To keep your weight at its current
level, you should remain at your daily caloric maintenance level.
To lose weight, you need to create a calorie deficit by reducing
your calories slightly below your maintenance level (or keeping
your calories the same and increasing your activity above your
current level). To gain weight you need to increase your calories
above your maintenance level. The only difference between weight
gain programs and weight loss programs is the total number of
calories required.
Negative
calorie balance is essential to lose body fat.
Calories
not only count, they are the bottom line when it comes to fat
loss. If you are eating more calories than you expend, you simply
will not lose fat, no matter what type of foods or food combinations
you eat. Some foods do get stored as fat more easily than others,
but always bear in mind that too much of anything, even "healthy
food," will get stored as fat. You cannot override the
laws of thermodynamics and energy balance. You must be in a
calorie deficit to burn fat. This will force your body to use
stored body fat to make up for the energy deficit. There are
3500 calories in a pound of stored body fat. If you create a
3500-calorie deficit in a week through diet, exercise or a combination
of both, you will lose one pound. If you create a 7000 calories
deficit in a week you will lose two pounds. The calorie deficit
can be created through diet, exercise or preferably, with a
combination of both. Because we already factored in the exercise
deficit by using an activity multiplier, the deficit we are
concerned with here is the dietary deficit.
Calorie
deficit thresholds: How low is too low?
It is well
known that cutting calories too much slows down the metabolic
rate, decreases thyroid output and causes loss of lean mass,
so the question is how much of a deficit do you need? There
definitely seems to be a specific cutoff or threshold where
further reductions in calories will have detrimental effects.
The most common guideline for calorie deficits for fat loss
is to reduce your calories by at least 500, but not more than
1000 below your maintenance level. For some, especially lighter
people, 1000 calories may be too much of a deficit. The American
College of Sports Medicine (ACSM) recommends that calorie levels
never drop below 1200 calories per day for women or 1800 per
day for men. Even these calorie levels are extremely low. A
more individualized way to determine the safe calorie deficit
would be to account for one's bodyweight or TDEE. Reducing calories
by 15-20% below TDEE is a good place to start. A larger deficit
may be necessary in some cases, but the best approach would
be to keep the calorie deficit through diet small while increasing
activity level.
Example
1:
Your weight is 120 lbs.
Your TDEE is 2033 calories
Your calorie deficit to lose weight is 500 calories
Your optimal caloric intake for weight loss is 2033 - 500 =
1533 calories
Example
2: Your calorie deficit to lose weight is 20% of TDEE (.20%
X 2033 = 406 calories)
Your optimal caloric intake for weight loss = 1627 calories
Positive
calorie balance is essential to gain lean bodyweight
If you want
to gain lean bodyweight and become more muscular, you must consume
more calories than you burn up in a day. Provided that you are
participating in a weight-training program of a sufficient intensity,
frequency and volume, the caloric surplus will be used to create
new muscle tissue. Once you've determined your TDEE, the next
step is to increase your calories high enough above your TDEE
that you can gain weight. It is a basic law of energy balance
that you must be on a positive calorie balance diet to gain
muscular bodyweight. A general guideline for a starting point
for gaining weight is to add approximately 300-500 calories
per day onto your TDEE. An alternate method is to add an additional
15 - 20% onto your TDEE.
Example:
Your weight is 120 lbs.
Your TDEE is 2033 calories
Your additional calorie requirement for weight gain is + 15
- 20% = 305 - 406 calories
Your optimal caloric intake for weight gain is 2033 + 305 -
406 = 2338 - 2439 calories
Adjust your
caloric intake gradually
It is not
advisable to make any drastic changes to your diet all at once.
After calculating your own total daily energy expenditure and
adjusting it according to your goal, if the amount is substantially
higher or lower than your current intake, then you may need
to adjust your calories gradually. For example, if your determine
that your optimal caloric intake is 1900 calories per day, but
you have only been eating 900 calories per day, your metabolism
may be sluggish. An immediate jump to 1900 calories per day
might actually cause a fat gain because your body has adapted
to a lower caloric intake and the sudden jump up would create
a surplus. The best approach would be to gradually increase
your calories from 900 to 1900 over a period of a few weeks
to allow your metabolism to speed up and acclimatize.
Measure
your results and adjust calories accordingly
These calculations
for finding your correct caloric intake are quite simplistic
and are just estimates to give you a starting point. You will
have to monitor your progress closely to make sure that this
is the proper level for you. You will know if you’re at
the correct level of calories by keeping track of your caloric
intake, your bodyweight, and your body fat percentage. You need
to observe your bodyweight and body fat percentage to see how
you respond. If you don't see the results you expect, then you
can adjust your caloric intake and exercise levels accordingly.
The bottom line is that it’s not effective to reduce calories
to very low levels in order to lose fat. In fact, the more calories
you consume the better, as long as a deficit is created through
diet and exercise. The best approach is to reduce calories only
slightly and raise your daily calorie expenditure by increasing
your frequency, duration and or intensity of exercise.
