Dao of Health and Nutrition - Evergreen State College



Dao of Health and Nutrition

Spring 2008

Body Composition: Body Fat Analysis

A. What is body fat percentage?

Body fat percentage refers to the amount of body fat mass in regards to the total body weight described in a percentage:

Body Weight can be divided into Fat mass and Fat-free mass (bones, blood, muscles, water).

Body fat percentage(%)= body fat mass/body weight x 100

Ratio of the body constituents in non-obese individual:

Water: 50-60%

Fat: Male: 10-20%

Female: 20-30%

Proteins: Male: 15-25%

Female: 8-18%

Minerals, Carbohydrates: 2-5%

B. Principles of body fat percentage measurement with a non-invasive bioimpedance analyzer:

Muscles, blood vessels, blood and bones are body tissues conduct electricity easily. Body fat have little electric conductivity. The Body Fat Analyzer (BFA) sends an extremely weak electric current (50 kHz and 500 μA) through your body to determine the amount of fat tissue. You will not feel the weak current while operating the BFA.

Voltage (V) = current (I) x resistance (R); V=IR

With constant current and measured voltage, the BFA calculates the resistance. The calculation equation used by Bioelectrical Impedance Method takes into consideration of weight, height, gender, age and athlete training status. Correct posture and consistent measuring conditions need to be maintained for the best results.

C. How to use the BFA:

Precautions:

1. Never use the BFA in combination with medical electronic devices (e.g. pacemakers)

2. Do not use BFA when your body/fingers are wet; do not put the analyzer in water.

3. Do not drop, vibrate or disassemble the unit.

Steps:

1. Enter your personal bio-data: use on/off to turn on power; up and down button to select Normal/athlete, height, weight, age, gender

2. Stand using correct posture to measure: see the attached diagram

3. Press Start button to start measurement. Please read and record:

Body Fat Percentage: ___________________ %

BMI: _______________________ (= weight lb/height in2 x 703)

D. With your enhanced understanding of the information provided in the course, discuss the relationship between BMI and Body Fat Percentage; the implications of the two parameters for your health, future nutrition and physical activity plans. Use the following table as a guide for the standard ranges of body fat percentage:

Recommended Body Fat Ranges in %

| |Age |Low |Recommended |High |Very high |

|Female |20-39 |5-20 |21-33 |34-38 |>38 |

| |40-59 |5-22 |23-34 |35-40 |>40 |

| |60-79 |5-23 |24-36 |37-41 |>41 |

| | | | | | |

|Male |20-39 |5-7 |8-20 |21-25 |>25 |

| |40-59 |5-10 |11-21 |22-27 |>27 |

| |60-79 |5-12 |13-25 |26-30 |>30 |

F. Other questions to ponder in your Lab reflections/analysis assignment:

1. Assuming that you begin to increase your daily exercise while maintaining the same body weight, what would you expect to see in your BMI and Body Fat percentage measurements in several months? Why?

2. If you maintain the same calories intake while you increase daily exercise, how would you anticipate your BMI and Body Fat percentage to change in a few months? Why?

3. If you go on a healthy diet and exercise regimen, with a decrease in your daily calories intake and an increase in your daily exercise, how would you anticipate your BMI and Body Fat percentage to change in a few months?

4. If a person has an elevated BMI but a normal range of body fat percentage, what do you think of his/her body composition? Can you deduce his/her physical fitness?

5. (supper challenge) The manufacturer of the BFA recommends measuring body fat percentage 2 hours after meals. Considering the concept of bioimpedance, can you figure out why one needs to wait for 2 hours after a meal for an accurate measurement?

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