Resistance-trained individuals who engage in progressive resistance training and consume high dietary protein intake (≥2.0 g/kg/day) experience simultaneous increases in fat-free mass and decreases in fat mass over periods of 6–10 weeks.

When a trained person lifts heavy weights and eats a lot of protein, the muscles sense the tension and start building more protein, while the body burns fat for energy instead of storing it. The protein provides building blocks that turn on muscle growth signals, and the extra calories from protein are burned off as heat instead of becoming fat. At the same time, stored fat breaks down to fuel the body, so muscle grows even as fat shrinks.