How To Calculate How Many Calories You Need To Eat Each Day…
The first step in designing your personalized nutrition plan is to calculate how many calories you need to eat per day. This will be based on your total daily energy expenditure (TDEE) which is the total number of calories that your body burns in 24 hours. TDEE is also known as your “maintenance calorie level”. Knowing what your maintenance calorie needs are will give you a starting point from which to begin your nutrition program.
Methods Of Determining Your Caloric Needs…
There are several different calorie calculation formulas that you can use to help determine your caloric needs. Most of them take into consideration your age, sex, height, weight, lean body mass, and activity level. But regardless of the formula that you use, they are all just estimates. There are so many metabolic and hormonal processes going on that there is no way to know for 100% certainty the exact number of calories one individual needs based solely on their physical stats. However, you can get close enough to plan out your nutrition program and then make adjustments as needed based on your actual results.
1) The “Quick & Easy Method” (based on bodyweight)
A fast and easy method to determine calorie needs is to simply use your current body weight times a multiplier.
Fat loss = 12 calories per pound of bodyweight
Maintenance = 15 calories per pound of bodyweight
Weight gain = 18 calories per pound of bodyweight
This is a very easy way to get a rough estimate of your 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 a lot more calories than this formula indicates. In addition, the more lean body mass one has, the higher the energy expenditure will be. Because bodyfat is not accounted for, this formula may greatly overestimate the caloric needs if someone has a very high bodyfat percentage. For example, a sedentary 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 & Easy Method” for fat loss).
More Advanced Methods Of Calculating Your Calorie Needs…
A much more accurate method for calculating TDEE is to first determine your 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 physical activity). 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 to keep your body alive.
But like I mentioned above, this is still just an estimate of your calorie needs. BMR can 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 metabolism and a high BMR. 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.
2) 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).
Note: This is the formula I use most often when designing a customized diet plan for one of my personal coaching students.
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.
Sample Calculation:
You are a 30 year old male.
You are 5′ 10″ tall (178 cm)
You weigh 185 pounds (84 kilos)
Your BMR = 66 + (13.7 X 84) + (5 X 178) – (6.8 X 30) = 1903 calories per 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)
Moderately 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)
Extra active = BMR X 1.9 (hard daily exercise/sports & physical job or 2X day training, i.e marathon, contest etc.)
Total Calorie Expenditure Per Day:
Your BMR is 1903 calories per day
Your activity level is moderately active (work out 4 times per week)
Your activity factor is 1.55
Your TDEE = 1.55 X 1903 = 2950 calories per day
3) Katch-McArdle formula (BMR based on lean body weight)
If you have had your bodyfat percentage tested and you know what your lean body mass is 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 the formulas based just 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 kilograms)
Sample Calculation:
You are male.
You weigh 185 pounds (84 kilos)
Your body fat percentage is 15% (27.75 pounds of fat, 157.25 pounds of lean mass)
Your lean mass is 157.25 pounds (71.5 kilograms)
Your BMR = 370 + (21.6 X 71.5) = 1914 calories
To determine TDEE from BMR, you simply multiply BMR by the “Activity Multiplier”.
Total Calorie Expenditure Per Day:
Your BMR is 1914 calories
Your activity level is moderately active (work out 4 times per week)
Your activity factor is 1.55
Your TDEE = 1.55 X 1914 = 2967 calories per day
As you can see, the difference in the TDEE as determined by both formulas is statistically insignificant (2950 calories vs. 2967 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 (i.e. very muscular or very obese).
Adjusting Your Caloric Intake According To Your Fitness Goals…
Once you know your TDEE (maintenance calorie level), the next step is to adjust your calories according to your primary physique transformation goal – gaining or losing weight.
The mathematics of calorie balance are simple:
To maintain body weight, you should strive to keep your daily caloric intake at maintenance level.
To lose body weight (i.e. burn bodyfat), you need to reduce your calories below your maintenance level.
To gain body weight (i.e. gain muscle mass) you need to increase your calories above your maintenance level.
The only real difference between a muscle building and a fat loss program is the total number of calories required. Your actual weight training workouts in the gym should be hard and heavy in both situations in order to stimulate muscle growth.
In the section on “Monitoring Your Progress” we’ll dive in deeper on how you can manipulate your calorie intake to ensure you are on the right track to reaching your muscle building and fat loss goals.
If you have any questions or comments about how to calculate your individual caloric needs,
please post them in the forum and we’ll chat there 🙂