Gauging Fat Loss vs Muscle Retention

This may be a rather simple answer, but I’m gonna ask it anyway.

I’m in the midst of cutting down to b/t 12-15 percent BF. It’s a loss of about 5 percent.

Along the way, I want to retain as much muscle as possible, obviously.

Is there a way to ensure that that objective is on track?

As my weight goes down, or as I notice my clothes fitting differently, or by what I see in the mirror - whatever the method for guaging my fat loss happens to be - if my lifts stay the same, does that in theory mean I have at least minimized my muscle loss?

I just want to make sure I have a way of ensuring I am on the right track.

In before the flaming begins<

Read the nutrition articles. Train as though you were building muscle.
Use skinfold calipers to measure bodyfat, or like I do, simply use a tailor’s tape to measure your girths, the more the better.
If you’re maintaining or increasing strength, your waist is dropping, your chest and arms for example or holding size or barely decreasing and you feel good or better, you’re obviously on the right track.

Calipers. After all, pinching the fat under the skin is the most direct way you have available to measure your progress.

Buy a cheap caliper like the $25 Slimguide. Follow the instructions in the manual to measure 4 sites and estimate BF% from the chart included. Measure a few other sites of interest too. (For example, take a measurement near your navel; even though it’s not used by the formula, for most of us it’s a site of interest.) From the BF% estimate, then calculate your LBM.

This may not be an accurate (i.e., true) estimate, but that’s OK. It is a reliable indicator of progress when you measure it each week or so.

Note that if you are following a low-carb diet, you can lose several pounds of LBM from glycogen depletion. This is not the same as losing muscle.

The only thing to worry about is pinching the exact same spot each week, in the same way. This can be harder than you’d think. I try to find a reference mole or freckle and make notes and even pictures of where I pinched. If there is no mark whatsoever, I make a fake one with a brown Sharpie. May sound silly, but I get reliable measures of progress and can really tell how my body is responding to whatever I have been manipulating.