Capacity 03 · Maintain Function
Signal · Body Fat %
Composition matters more than weight.
Body fat percentage answers the question the scale cannot: of the weight you carry, how much is lean and how much is fat? Two people at the same weight can be at very different places on the composition spectrum — and it is composition, not weight, that predicts function and risk.
The ranges that matter
Three bands. One direction.
What matters most is the direction over time under the same conditions — is the number trending toward the Fit band, or drifting away from it?
Fit / Optimal
M ≤ 17 % · W ≤ 24 %
Functional composition. Enough fat for hormonal and reproductive health, not so much that recovery or insulin sensitivity suffer.
Well
M 17 – 24 % · W 24 – 31 %
Acceptable but wider than optimal. Often associated with rising VAT and falling recovery capacity. Worth shifting.
Sick / At Risk
M > 24 % · W > 31 % (severe M>32, W>40)
Elevated fat mass. Rising risk of metabolic dysfunction, inflammation, and functional decline independent of total weight.
What it reveals
The scale is not the signal.
Body weight is a noisy signal. It lumps muscle, bone, fat, and water into one number and hides what is actually happening under the skin. Two people the same weight can be in very different metabolic worlds.
Body fat percentage separates the two. In men, functional ranges are roughly 8–18%; in women, 18–28%, reflecting the higher essential fat stores women carry for reproductive and hormonal health. These are bands, not targets — going below the low end is not 'more fit.'
Too little body fat is its own failure mode: hormonal disruption, poor recovery, stress-fracture risk, immune compromise. Too much — especially when it is visceral — drives inflammation and degrades every other capacity.
Body fat % lives in Maintain Function because composition is the frame the rest of your capacities act through. A body in a functional composition range recovers faster, handles fuel better, and preserves strength and bone more easily.
On the floor
Chasing the scale alone will eventually lead you astray. Scan composition every 6–12 months. Optimize for composition, not weight — and accept that good composition usually means slightly heavier than you thought, not lighter.
What moves it
Work the system, not the number.
First levers
- Lift heavy things 2–4 sessions per week to protect lean mass during fat loss.
- Anchor protein at 0.7–1.0 g per pound of target weight.
- Eat mostly whole, unprocessed food; remove liquid sugar from the diet.
- Modest calorie deficit when losing fat; surplus when actively adding mass.
Second levers
- Protect sleep; sleep debt preferentially costs lean and preserves fat.
- Zone 2 aerobic base supports fat oxidation and recovery.
- Don't over-restrict; chronic under-eating costs muscle and bone.
- Re-scan every 6–12 months. Measure composition, not weight.
Why it sits with "Maintain Function"
Body Fat % sits among four Maintain Function markers. Read with
ALMI,
BMD, and
Grip Strength — together they describe the body's structural reserve.
Go deeper
Coaching and education only. Not medical diagnosis or treatment. Excerpts welcome with attribution to metabolicradar.com.