I’ve been chasing after getting to a lower body fat for a while now. Here is the chart of my body fat percentages between October 24, 2017 and today (from my Nokia Body+ scale).
Monthly Data Points (Fat/Lean)
Ideal Body Fat Percentage
For my age, 20.9% is considered my ideal body fat percentage so I’ve hit that number but I really want to get to 15% body fat.
Losing Lean Body Mass
The apparent problem is that my Lean Body Mass (LBM) is also dropping at the same time. I’ve lost 19.6 lbs since November. Of that 10.7 lbs were fat but I’ve also lost 8.8 lbs of Lean Body Mass.
What constitutes Lean Body Mass? Most importantly am I losing muscle? Here the scale seems less useful. It does present a muscle percentage but the results are odd. Of the 8.8 lbs loss of LBM 5 lbs were “muscle”. Here’s the muscle values from the scale added in:
So the good news is that my muscle percentage is going up and my fat percentage is dropping down. The bad news is this shows me as down 5 lbs of muscle. Considering I have been training through this time, that’s a concern.
That also means that I am chasing after a number which keeps slipping away. If the 19.5% body fat number from 4/1/18 is correct then I’ve still got to lose 4.5% more body fat to get to 15% body fat. But losses have been averaging 55% from body fat and the rest from LBM. So I’d need to lose more like 4.5% divided by 55% or 8% of my current weight to get to 15%. At 171 lbs that’s 13 more lbs. That would put me at 158 lbs.
Why Trust the Scale?
At least one study indicated that Body Impedance Analysis (BIA) is reliable (Assessment of fat-free mass using bioelectrical impedance measurements of the human body. H C Lukaski P E Johnson W W Bolonchuk G I Lykken. The American Journal of Clinical Nutrition, Volume 41, Issue 4, 1 April 1985, Pages 810–817).
These data indicate that the bioelectrical impedance technique is a reliable and valid approach for the estimation of human body composition. This method is safe, noninvasive, provides rapid measurements, requires little operator skill and subject cooperation, and is portable. Further validation of this method is recommended in subjects with abnormal body composition.
I also have an external data point that correlated well to the scale. Last year (10-27-2017), I went and got a BodPod measurement. So, I trust the scale is “close enough”.
On the other side… from this site (THE PITFALLS OF BODYFAT “MEASUREMENT”, PART 4: BIOELECTRICAL IMPEDANCE (BIA)):
BIA can be problematic because it’s a prediction based off of a prediction, so the error gets compounded. When you look at group averages for BIA measurements, there tends to be bias, with BIA often underpredicting how much fat you have. As with other techniques, the individual error rates can get high, with some research showing error rates of around 8-9%. In fact, BIA doesn’t do much better than BMI at predicting body fat in some cases. When it comes to measuring change over time, BIA can often underpredict the amount of fat loss, and the estimated change can be off by up to 8%.
What BIA numbers Mean
When the scale says 75% muscle what does that mean? The scale has five numbers
- Body Fat %
- Muscle %
- Water %
- Bone %
The Nokia support shows:
Fat mass + Bone mass + Muscle mass = 100% of the body composition
As there is water in muscle and fat, the water mass cannot be added to the other metrics when calculating the body composition.
So water mass is separate from the other numbers. Makes sense since everything is made up of a lot of water.
Total body water is the total amount of fluid in the body. It includes the intracellular water and the extracellular water that represents the amount of water contained in both the cells and the tissues.
For example, body fat contains approximately 10% water, while muscle is approximately 75% water.
Adding in the water numbers:
Correlation to Other Information
These numbers are not too close to the US Navy Body Fat Calculator which has me currently at 17%.