Question about scales - fat and muscle

LKArgh

Today my daughter had an appointment with a dietician, she is almost 18 and starting to form some anxiety regarding her weight and trying to get a balanced diet.
I was in the appointment since she is a minor, and in general I think what she said was good - do not count calories at her age, add strength training to cardio, emphasis on protein, vegetables and healthy fats, talked a lot about body composition and about the importance of maintaining muscle plus a lot of things about eating disorders and peer pressure for teens and young adults.
So in general it was a good experience, the advice she gave seemed totally reasonable and they have a plan to meet twice per month.
What I am a little skeptical about is how she did measurements. She had a scale where you step barefoot and then hold a kind of rod I guess? According to her measurements, my daughter has low muscle mass, which she has probably caused by reducing protein too much. I think the conclusion is correct as is the reasoning but I wonder about the accuracy. Can you make even a general assumption based on such a scale and not calipers?

steveko89

Bio-impedence scales (what was used here) have a pretty hefty performance band and can easily be skewed by water retention, food mass, perspiration, etc. However, compared to calipers, they probably have the same, if not less variability and would be quicker and less invasive to use in a clinical setting. In terms of trend observation, using an electronic device rather than a mechanical one dependent on the user would provide better less noisy analysis over many data points.

However, I wouldn't put too much stock in either method. Quantifying body fat % or lean mass and getting hung up on the numbers themselves is a good way to lose sight of the overall goal of body composition improvement. Those metrics can be one component to assess progress but other measures like progress photos, bodily circumference measurements, program adherence, strength gains, and qualitative aspects such as sleep quality, energy levels, or feeling of well-being are all useful indicators.

westrich20940

The measurements for stuff like that should be used to look at overall/general trends, not absolute numbers.

Your daughter may very well have low muscle mass. The key is to pick a measuring method and then continuing to use it and see if her muscle mass is increasing. You can absolutely also ask the dietician about her methods as well.

heybales

And unless she shows up to her next visit exactly the same hydration level and food in stomach - she didn't even get a useful data point to compare with next visit.

Call it a 10% range of accuracy for the either fat mass or non-fat mass side of things, if you measure under the same conditions.

And it's sad, but I'm betting the nurse/Dr read the figure for LBM (Lean Body Mass - everything not fat mass, including water), and called it muscle mass, if they indeed used that term.
Which means a lack of understanding for what that is.

If it was a scale that showed a figure for muscle mass on it's own, that's even less accuracy than just a plain BF% scale.

Reminds me of when a traveling RMR test van would show up at the mall or a gym and offer a resting metabolism test at say 50% their normal price - knowing full well if the people ate in the last 3-5 hrs, or were very active, the resulting figure was nonsense and useless.