A better way to set target goals

jaybird180

I'm trying out a new BioImpedence Analysis Scale and have collected 5 new datapoints over the last 6 days of ownership. The scale measures Weight, Bodyfat%, Muscle Mass% and Water%. I'm thinking that instead of using weight as a goal, that I should use Bodyfat% loss and Muscle% maintenance as goals. I suppose that I'm having a math problem in deriving a suitable goal weight to tell MFP what my new goal weight should be as it can only consider weight, instead of using any of the other 4 metrics. As we all know, MFP uses current weight and goal weight with a factor of time to calculate calorie consumption goals for the user. Any suggestions on how I can solve this math problem?

richardgavel

The one concern is that the weight will be a lot more accurate a measure than BF%.

LHWhite903

It's a very good aspiration. Still, what richardgavel says has merit, BF% isn't easy to measure accurately.

Erik8484

Most likely, your bodyfat% is not what your scale says it is, because BIA scales are very unreliable. I've seen examples on this forum where it has been off by more than 10% (i.e. scale says 20% bodyfat, a more reliable test returns 30%).

However, if your scale was correct, you would run the maths as follows:
Current weight = X lbs, current bodyfat = Y%, target bodyfat = Z%
Current lean body mass = X lbs * (1 - Y%) e.g. 300 lbs at 40% bodyfat means you have 60% lean mass, 300 lbs x 60% = 180lbs lean body mass
Target weight = lean body mass / (1 - Z%) e.g. 180 lbs lean body mass makes up 85% (or all but 15%) of your total weight = 212 lbs.

If you set that as your target you would implicitly be assuming that you won't lose or gain any lean body mass while burning fat (including muscle, water, skeletal mass), which is a simplifying assumption and not likely. Alternatives would include setting a lean body mass target, or updating your goal weight as you progress based on feedback from your scale (which, to reiterate, is probably not accurate).

cityruss

BioImpedence is far too unreliable to make your endeavor worthwhile.

jeepinshawn

cityruss wrote: »

BioImpedence is far too unreliable to make your endeavor worthwhile.

Everything I have tag indicates this is unfortunately true. Bodpod or dexa scan are the most common accurate bf measurements.