Skinny Girl's Quest for Muscle

Skinny Girl's Quest for Muscle
Getting Started Part 2: How Fat Am I? Really?

Applying the math and formulas from Part One is the easy part, but coming up with what exactly it should be applied is definitely a test of estimation skills.

Inputs: Weight

Coming up with my starting weight is easy. According to my Tanita bathroom scale, I weigh approximately 125 lbs, give or take a pound upward or downward over the course of the week. This amount will be converted to kilograms for the final calculation.

Weight in Pounds: 125
Weight in Kilograms: 56.7

Inputs: Body Fat/Lean Mass

My Tanita also claims to provide a Body Fat reading (as well as Lean Mass, Hydration, Visceral Fat, Bone Mass, and separate segmental readings for each body segment: a body fat rating for my right arm, left arm, right leg, left leg, trunk, and Lean Mass for each of the listed body segments as well.) And, to deliver this information, the scale requires that the user input gender, height, birthdate, and an athletic factor (depending upon how much the user exercises--if the answer is a whole lot, you are althletic.) Once the user complies with the setup requirements and steps on the scale, the Tanita sends a little electric pulse through the body measuring impedence. A fast signal speed means very little impedence, and lower fat in the body of the user as fat slows the signal's rate of travel.

With all of this information I'm there right--just pop the values into my formulas? Not so fast. I've noticed a significant difference in readings at different times during the day--I'm always really fat in the morning! After exercise, guess what? I'm thin again. I'm usually thin after drinking a large amount of water as well.

Being even more adventerous, I've even tested uing the "Male" instead of "Female" settings. As a "Male" I'm carrying over 10% less body fat! Wow, that's a tremendous difference.

For day-to-day differences, the Tanita seems fairly reliable as long as I test myself under the exact same conditions every day: first thing in the morning (before drinking water, showering, walking around, etc.) I've tracked my tests for the last year and found them much more consistent with using these similar testing conditions. Further investigation into bioimpedence body fat measuring suggests that factors such as hydration and body temperature significantly affect measurments.

This is great if all I were using the scale for is to track progress. However, when attempting to plan my nutrition program, the data just isn't accurate enough. And really, who wants to run around believing they have 27% body fat if the true amount is only 20%?

To remedy the situation, I've done some research and found suggestions such as measuring body fat under both the male and female setting, averaging the two values and subtracting 1 percent from the total(1). I'm also considering using a service with a more accurate testing method (Bod Pod testing(2)), and using my personal trainer's caliper test. Until then, I've decided to start with the averaging method just for nutritional purposes.

Body Fat Using Female Settings: 26.2%
Body Fat Using Male Settings: 17.1%
Average of Above Minus 1%: 20.7%

So, now we've set a Body Fat value, what about Lean Mass? My Tanita suggests that my Body Mass is:

Body Lean Mass using Female: 86.8
Body Lean Mass using Male: 97.4
Average of Above Minus? Plus?

Unfortunately, I can not re-work the formula because fat percentage points in the first formula can not be translated to pounds of lean in the second formula. Additonally, instead of subtracting lean, one would add lean to make up for the difference of using a lower body fat (by 1%). So in this case, how about we back into a number using what we learned in Part One.

Weight in Kilograms: 56.7
Percent Fat: 20.7

Total Kilograms of Fat: 56.7 x 0.207 = 11.7
Total Weight Minus Fat: 56.7 - 11.7 = 45

Lean Body Mass in Kilograms: 45


Inputs: Activity Factor

As mentioned in Part One, I'm using an "actual" basis for calculating activity calories burned, therefore, for my Activity Factor, I'm using the Sedentary multiplier.

Activity Factor: 1.2 (Sedentary)

Inputs: Average of Actual Calories Burned

Also mentioned in Part One, I am able to track actual calories burned and will be using that value in place of an Activity Factor that accounts for exercise. Starting July 1 and ending today, I've tracked an additional 9,568 calories burned from exercise outside of my daily routine. There were 26 days during that time period. So, in order to calculate my daily average, I simply divide 9,568 by 26 = 368 calories per day.

Calories: 368

Summary

My inputs into the formula will be as follows:

Weight in Kilograms: 56.7
Lean Body Mass in Kilograms: 45
Activity Factor: 1.2 (Sedentary)
Calories: 368


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references

(1) Iron Girls [URL]
(2) Bod Pod [URL]