Unit 4

Discussion: How Active Are You?

Approximating Hour-To-Hour Calorie Needs For Men And Women Based On Body Weight, Height, Age & Activity Level

Basal energy expenditure (BEE) or basal metabolic rate (BMR) as it is sometimes called, is the energy requirement 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 we are doing here. We are 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 abstract 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 (see research abstract below). Given that there were far fewer obese people around back in the early 1900s than there are today, you should be aware of this weakness.

To partially offset this inherent weakness, the calorie charts below are based on one's lean body weight (LBW means fat-free weight). The simple logic for doing this is that 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, the assumption is made that for any given LBW in the tables below, the BEE is based on an average person with an average percentage of body fat. Since the Harris-Benedict equation uses total body weight, we are assuming that (for example) a woman with 100 pounds of lean body weight, and is 20% body fat, actually weighs 125 pounds. And a man with 170 pounds of lean body weight, and is 15% body fat, actually weighs 200 pounds.

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)
Where:
W = actual weight in kilograms (1 kg = 2.2046 pounds)
H = height in centimeters (2.54 cm per inch)
A = age in years

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 basal. Once you have determined your BMR, you must estimate your actual metabolic rate. You do this by computing how many minutes you spend in your various activities each day, and adding the total caloric cost of these activities to your BMR. To simplify this task, we have divided calorie-burning activities into five levels from very light to very heavy. The results you derive are only an estimate, but should nonetheless give you an idea of your daily caloric needs.

* The caloric cost of highly intense activities such as Nordic skiing or marathon running may be more than double your BMR.

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!

Average Daily Activity Level

To estimate your average activity level for a 24 hour period, read the INSTRUCTIONS below. You will easily be able to approximate the percentage that most closely describes your lifestyle. This percentage is used in the daily caloric expenditure charts below.

Instructions For each of the 24 hours in one of your "average" days, determine your energy expenditure by reading the descriptions below. Then, multiply your hourly BEE (BEE divided by 24) times your energy expenditure. For example, if your hourly BEE equals 85 calories, and your activity level during that hour was light (1.3), then you simply multiply 85 times 1.3. Your hourly caloric expenditure equals 110.5 calories. Do this for each hour of the day, add all of them together, and that is your daily caloric requirement (your metabolic rate). Be SURE to apportion your daily calories over at least five meals, with 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.

The caloric expenditures listed in the table below are for people with about a 20 percent 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 exercises with weights (including, but not limited to, 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.

Discussion

After you have determined your lifestyle activity “status” (i.e., couch potato, fitness buff, hard training athlete):

1. 1) Visit the discussion board and participate in a group discussion regarding what you have learned from this activity about the relationship between physical activity, energy expenditure and caloric costs.
2. 2) Start one (1) new thread and respond to at least two (2) separate threads, for a total of three (3) contributions to the discussion, for discussion points.

Click on Blackboard's Discussion button and scroll down to find, read, and participate in this unit's discussion. To read the Discussion Threads efficiently, follow these instructions:

1. Open a forum.
   • Click Show Options.
     • Use the check boxes to select the messages you want to view.
     • Click Collect in the options.
2. Read the text from all the selected messages.
• Print them if necessary.
3. Respond to posts individually.
   • Type your responses in a text file on your local hard drive. Save.
   • Copy and paste the text into the discussion thread in Blackboard. Submit.