Body Composition · GLP-1

Body Fat % Calculator
for GLP-1 Users

Track fat vs lean mass loss on GLP-1 medication. Uses the US Navy method — accurate to within 3–4% of DEXA scanning.

Measure at navel level
Measure at widest point
Your body composition results
Body fat %
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Fat mass
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lbs
Lean mass
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lbs
Results are estimates based on published research. Individual results vary. Not medical advice.
Based on your results
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From $199/mo
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About this calculator

Why body fat matters more than weight on GLP-1

The scale measures total body weight including fat, muscle, bone, water, and organs. When you lose weight on GLP-1 medications, ideally most of that loss is fat — not muscle. Tracking body fat percentage tells you whether your GLP-1 treatment is producing the right kind of weight loss.

Clinical trial data shows approximately 25 to 40% of weight lost on semaglutide without intervention is lean mass. With adequate protein intake (0.7 to 1.0g per pound of goal weight) and resistance training, this drops to 15 to 25%. Monthly body fat tracking catches disproportionate muscle loss early, when it's easiest to correct.

US Navy method accuracy: Within 3 to 4 percentage points of DEXA scanning. Most accurate when measurements are taken at the same time of day, in the same conditions, each month.

Healthy body fat ranges by sex

Women: Essential fat 10–13% · Athletic 14–20% · Fitness 21–24% · Acceptable 25–31% · Obese 32%+

Men: Essential fat 2–5% · Athletic 6–13% · Fitness 14–17% · Acceptable 18–24% · Obese 25%+

Frequently asked questions
GLP-1 medication preferentially targets fat loss but also causes muscle loss without adequate protein intake. DEXA scan data from GLP-1 trials shows approximately 60 to 75% of weight lost on semaglutide is fat mass when protein intake is adequate. Without intentional protein and resistance training, that figure drops to 45 to 60%. Tracking body fat percentage monthly tells you whether you are losing fat or disproportionate muscle.
The US Navy method is accurate to within 3 to 4 percentage points compared to DEXA scanning, making it the most reliable tape-measure method available without specialised equipment. Accuracy is highest when measurements are taken consistently — same time of day, same technique, ideally before eating. For tracking changes over time rather than absolute accuracy, the Navy method performs well when measurements are taken under consistent conditions.
Tracking both gives significantly more useful information than either alone. Scale weight can be misleading because water retention, hormonal fluctuations, and muscle mass changes can mask fat loss for days or weeks. Body fat percentage, measured monthly, tells you whether the weight you are losing is fat or muscle. If scale weight drops but body fat percentage stays the same, you are losing disproportionate lean mass.
The two most evidence-based strategies are high protein intake and resistance training. Protein targets of 0.7 to 1.0 grams per pound of goal body weight per day significantly reduce muscle loss during caloric restriction. Resistance training two to three times per week signals your body to maintain muscle tissue even in a calorie deficit. Creatine monohydrate at 3 to 5g daily has emerging evidence for additional lean mass preservation during GLP-1 treatment.
Lose fat, not muscle — from $146/mo Yucca Health · Clinical support
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Yucca Health · Clinical support
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