Lean body mass calculator for PSMF
Lean body mass is everything in your body that isn’t fat: muscle, bone, organs, water. Enter your weight and height to get an estimate. If you have a body fat reading from a scan, add it for a second number.
Why lean body mass comes up on a PSMF
The point of a PSMF is to lose fat while keeping as much lean mass as you can. Some people use lean body mass to set protein, and some track it to see whether they are losing muscle along with fat.
For people with obesity, the Cleveland Clinic protocol sets protein from ideal body weight, not lean body mass. Use the PSMF protein calculator for your daily target. This page is a cross-check.
How the estimate works
The calculator uses the Boer formula, published in 1984. It estimates lean body mass from weight in kilograms and height in centimeters:
- Men: 0.407 × weight + 0.267 × height − 19.2
- Women: 0.252 × weight + 0.473 × height − 48.3
If you enter a body fat percentage, the calculator also works out weight × (1 − body fat %). That second number is only as good as the body fat reading you put in.
How accurate is it?
Not very, for any one person. Boer built the formula from a group of 66 healthy adults, and it guesses lean mass from size alone. It can’t tell a muscular 100 kg person from one who carries more fat at the same height. Use it as a rough guide.
Measured methods are better. A DEXA scan is the usual clinical reference. Bioimpedance scales are cheap and easy, but the reading shifts with how much water you’re holding, and water shifts a lot in the first weeks of a PSMF. If you track body fat with a scale, weigh at the same time each day and look at the trend over weeks.
What to do with the number
If your Boer estimate is close to your ideal body weight, the two ways of setting protein will give similar targets. If your lean body mass comes out well above your ideal body weight, you may carry more muscle than average. Show both numbers to your doctor or dietitian and let them choose your target.
Read what PSMF is and who should avoid it before you start.
Sources
- Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. American Journal of Physiology 247(4 Pt 2):F632-F636 (1984)
- Chang J, Kashyap SR. The protein-sparing modified fast for obese patients with type 2 diabetes: what to expect. Cleveland Clinic Journal of Medicine 81(9):557-565 (2014)