by Frederick C. Hatfield, Ph.D.
Basal energy expenditure (BEE) or basal metabolic rate (BMR) as it is sometimes called, is the energy required to maintain life. It is measured at rest, but not asleep, in a thermo-neutral environment in the post-absorptive state. It can be measured directly or indirectly, or it can be estimated as I have done in this article. I am using the equations of Harris & Benedict (1919).
The Harris-Benedict Equation for estimating one’s BEE accounts for gender, age, height and weight. As the research abstract appended below indicates, the BEE derived using this equation for obese people are somewhat overestimated. That is, the equation appears to be reasonably accurate for normal people with normal body fat. Given that there were far fewer obese people around back in the early 1900s than there are today, you should be aware of this minor weakness. Here are the equations:
For men, the B.E.E. = 66.5 + (13.75 x W) + (5.003 x H) – (6.775 x A)
For women, the B.E.E. = 655.1 + (9.563 x W) + (1.850 x H) – (4.676 x A)
W = actual weight in kilograms (1 kg = 2.2046 pounds)
H = height in centimeters (2.54 cm per inch)
A = age in years
There’s another factor that you should be aware of. For any given body weight, the person with the lowest percentage of body fat is going to burn more calories. Bigger muscles burn more calories than do little ones. Thus, when using the tables below, which are based on an average person with an average percentage of body fat, bear in mind to add or subtract from the tabled figures accordingly. Since the Harris-Benedict equation uses total body weight, we are assuming that (for example) the average woman back in the year 1919, with 100 pounds of lean body weight, and 20% body fat, actually weighed 125 pounds. And a man with 170 pounds of lean body weight, and 15% body fat, actually weighed 200 pounds.
Determining Your Average Daily Caloric Needs
Obviously, there is more to life than just resting in that temperature-neutral environment. You must also have energy from your diet to support your activities above your basal level. Once you have determined your BMR, you must estimate your actual metabolic rate. You do this by estimating how much your daily activities “cost” you each day, and adding the total caloric cost of these activities to your BMR.
To simplify this task, we have divided several activities into five levels from “very light” to “very heavy” (see Table One). The results you derive are only an estimate, but should nonetheless give you an idea of your daily caloric needs.
|Table One: Average Daily Physical Activity And Its Caloric Cost|
|Average Couch Potato||Average Fitness Buff||Average Hard Training Athlete|
|Very Light||Light||Moderate||Heavy||Very Heavy|
|1.2 – 1.3 X BEE||1.4-1.5 X BEE||1.6-1.7 X BEE||1.8-1.9 X BEE||2.0+ X BEE|
|Your daily activity schedule includes an hour or more of these types of activities|
Light weight training
Intense weight training
The higher your body fat percentage, the fewer calories you’ll burn (lower activity level, and less muscle to burn calories). The lower your body fat percentage, the more calories you’ll burn (bigger muscles burn more calories than little ones). Thus, it becomes much easier to get rid of fat permanently by increasing your metabolic rate. You do this by increasing both your muscle mass and your activity level. You can (and SHOULD) gain muscle mass and lose fat at the same time. Never sacrifice muscle tissue during the fat loss process. Instead, build more muscle to burn more calories. You’ll lose more fat faster, and you’ll be more likely to keep it off. The KEY is to control your calories!
The “Quick Check” Method
The caloric expenditures listed in Table Two are for people with about a 20% body fat level. The smaller your muscles are, the fewer calories you’ll burn; the bigger your muscles are, the more calories you’ll burn. That means that the higher your proportion of fat is to your total body weight, the fewer calories you’ll burn. On the flip side of the coin, the greater your proportion of muscle to your total body weight, the more calories you’ll burn. Remember that strenuous exercise with weights (including dumbbells and barbells, Nautilus-type machines, your own body weight, and other forms of resistance exercises) is the best way to increase your muscle size, thereby increasing your metabolic rate. This will result in far more calories being burned all day long, even at night while you’re sleeping. This, in turn, makes it easier to keep your body fat level in check.
|Table Two: Activities And Their Approximate Hourly Caloric Cost For Different Body Weights|
|If You Weigh…||100||125||150||175||200||225||250||275||300|
|Walking 2.5 Mpg||104||154||204||254||304||354||404||454||504|
|Light Weight Training||172||222||272||322||372||422||472||522||572|
|Walking 3.75 Mph||199||249||299||349||399||449||499||549||599|
|Swimming 2.5 Mph||199||249||299||349||399||449||499||549||599|
|Medium Weight Training||342||392||442||492||542||592||642||692||742|
|Heavy Weight Training||512||562||612||662||712||762||812||862||912|
|Cycling 13 Mph||560||610||660||710||760||810||860||910||960|
Determining Your Hourly Calorie Need
A more precise method for determining your caloric need is to compute it hour-by-hour.
For each of the 24 hours in your “average” day, determine your energy expenditure by reading the descriptions in Table Three. Then, multiply your hourly BMR (BMR divided by 24) times your energy expenditure. For example, if Bob Jones’ hourly BMR equals 85 calories, and his average activity level during that hour was 300 percent above BMR, you simply multiply 85 times 3.00. His hourly caloric expenditure equals 255 calories. Remember, most people intersperse each hour of heavy activity with brief quiescent periods (e.g., resting 5 minutes between sets or chatting with your training partner during a workout). Therefore, it is important to get an AVERAGE for that hour! You may have to break each hour of activity down into briefer periods for the sake of accuracy. Do this for each hour of the day, add all of them together, and that is your daily caloric requirement.
Be SURE to apportion your daily calories over at least five meals, with the size of each meal reflective of your UPCOMING caloric needs. For example, if you expect to train, eat more; if you expect to take a nap, eat less.
|Table Three: Energy Expenditure Guide|
|90%||100%||Lying down totally relaxed but not sleeping (this is your “basal metabolic rate”)|
|180%||200%||Very Light: Sitting, studying, talking, little walking or other activities.|
|270%||300%||Light: Typing, teaching, lab/shop work, some walking.|
|360%||400%||Moderate: Walking, jogging, gardening type job.|
|450%||500%||Heavy: Heavy manual labor such as digging, tree felling, climbing.|
|540%||600%||Exceptionally Heavy: Fitness-oriented weight training, aerobic dance, cycling or similar vigorous activities.|
|630%||700%||Sports: Vigorous sports competition such as football, racquetball, tennis or other extended-play sports activities.|
|720%||800%||All-Out Training: Extremely high intensity weight training with little rest between sets or exercises.|
|810%||900%||Extended Maximum Effort: Extremely high intensity and high duration sports competition such as triathlon, cross country skiing or marathon.|
For example, Bob Jones weighs 161, and his lean body weight is 159 (fat weight is 9) with 5.7% body fat. His BMR is 1750. Let’s look at his day (Table Four).
|Table Four: Zigzag Eating For Daily Activities|
|Daily Activities||Cost in Calories||Calories per Meal*
(Upzig / Downzag)
|12 midnight – 1:00 am||1750 / 24 X .8 = 58.3|
|Total Calories Burned While Asleep = 466
Bob Jones’ energy needs during sleeping hours will be derived from fat stores mobilized by hGH.
|8-9 (Meal)||1750 / 24 x 200 = 146||510 + or – 80
(430 / 590)
|9-10 (Office Work)||1750 / 24 x 2.5 = 182|
|10-11 (Office Work)||182|
|11-12 Noon (Meal)||146||656 + or – 80
(576 / 736)
|12 Noon – 1 (Labor)||1750 / 24 x 4.5 = 328|
|1-2 (Office Work)||182|
|2-3 (Meal)||182||947 + or – 80
(867 / 1027)
|3-4 (Workout)||1750 / 24 x 8 = 583|
|4-5 (Office Work)||182|
|5-6 (Meal)||182||546 + or – 80
(466 / 626)
|8-9 (Meal)||182||684 + or – 80
(604 / 764)
|9-10 (Computer Work)||182|
|11-12 Midnight (TV)||160|
|TOTAL||3343||3343 (2943 / 3743)|
* The caloric value of each meal is predicated on the caloric cost of upcoming activities. Then, approximately 400 calories are added to workout days and subtracted from days in which there is either no workout or workouts for smaller muscle groups. In this example, that would equal 80 calories added to or subtracted from each of 5 meals. This “zigzag” pattern ensures both muscle gain and fat loss.
David C. Frankenfield, MS, RD, Eric R. Muth, MS, and William A. Rowe, M.D. Harris-Benedict studies of human basal metabolism: History and limitations. Journal of the American Dietetic Association April 1998
In the early part of the 20th century, numerous studies of human basal metabolism were conducted at the Nutrition Laboratory of the Carnegie Institution of Washington in Boston, Mass, under the direction of Francis G. Benedict. Prediction equations for basal energy expenditure (BEE) were developed from these studies. The expressed purpose of these equations was to establish normal standards to serve as a benchmark for comparison with BEE of persons with various disease states such as diabetes, thyroid, and other febrile diseases. The Harris-Benedict equations remain the most common method for calculating BEE for clinical and research purposes. The widespread use of the equations and the relative inaccessibility of the original work highlights the importance of reviewing the data from which the standards were developed. A review of the data reveals that the methods and conclusions of Harris and Benedict appear valid and reasonable, albeit not error free. All of the variables used in the equations have sound physiologic basis for use in predicting BEE. Supplemental data from the Nutrition Laboratory indicates that the original equations can be applied over a wide range of age and body types. The commonly held assumption that the Harris-Benedict equations overestimate BEE in obese persons may not be true for persons who are moderately obese.
(J Am Diet Assoc. 1998; 98:439-445.)
Based on data contain in: Harris J, Benedict F. A biometric study of basal metabolism in man. Washington D.C. Carnegie Institute of Washington. 1919.