In the Zone block calculation example, if body fat is 20% and present weight is 140 lb, what is the lean body mass?

• A. 28 lb
• B. 112 lb
• C. 140 lb
• D. 120 lb

Answer: (B)

Lean body mass is everything except fat mass. To get it, subtract the fat mass from total weight. Fat mass = 0.20 × 140 = 28 lb. Then lean body mass = 140 − 28 = 112 lb. So the lean body mass is 112 lb. The other numbers reflect common confusions: 28 lb is the fat mass, not lean mass; 140 lb would be if there were no fat; 120 lb would imply only 20 lb of fat (about 14% body fat), which is not 20%.