body fat or BMI--which should we track

Question
I work in a setting where we often have weight loss groups/competitions, kind of like the "Biggest Loser". We all put in a few dollars and the one who loses the most wins the pot. Well, I would like to make the losses mean more and level the playing field, so to speak. Should track changes in BMI or changes in body fat percentages over the 12 week program? I have a hand held BEI device. It is certainly far from state of the art, but it does give consistent readings. What would you say is a fairer way to compare people's progress?

Answer
Hi Sarah,
Thanks for the question.  Hands down - go with the body fat percentage.  BMI does not account for muscle mass gains that might be made during weight loss.  So if someone gains muscle they will be penalized on the BMI.  Body fat percentage will account for changes in muscle mass.  Please note that body fat percentage via an Omron brand hand held analyzer will vary based on fluid intake. The higher the fluid intake, the lower the body fat percentage.

The reason the biggest loser has always used the scale is it is easy and accurate when weight loss is the goal.  The problem with the scale is that it will not differentiate between whether the weight came from fat, muscle, or fluid.

There are many different ways to measure change.  I would use two measures, the overall weight loss and the body fat percentage.  You could total the drop in weight and drop in body fat percentage for each person and use that as the "scoring" method.

I hope this helps, and glad to hear you are doing the competition.  Competition brings out the best possible performance in people!

Let me know if I can provide additional information.

Best of health,
Dr. Bret
doctoremery.com

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