Resting metabolic rate, the calories burned by the body at rest, accounts for approximately 60 to 70 percent of total daily energy expenditure. The primary determinant of resting metabolic rate is lean body mass, specifically muscle tissue, which is considerably more metabolically active than fat tissue. This is why body composition rather than body weight is the metric that matters most for long-term metabolic health.
The Numbers
Each kilogram of skeletal muscle burns approximately 13 calories per day at rest. Each kilogram of fat burns approximately 4 calories per day at rest. An adult who gains 5 kilograms of muscle over two years of resistance training increases their resting metabolic rate by approximately 65 calories per day, or 450 calories per week, without any change in activity level. Compounded over years, this is a clinically significant change to the energy balance equation.
The Metabolic Cost of Dieting Without Resistance Training
Caloric restriction without resistance training produces weight loss that is approximately 25 to 30 percent from lean mass and 70 to 75 percent from fat. The loss of lean mass reduces resting metabolic rate, making subsequent weight management more difficult. This is the mechanism of yo-yo dieting: each cycle of restriction and regain leaves the resting metabolic rate lower and the body composition less favourable.
The Practical Priority Order
- Resistance train two to three times per week to build and preserve muscle mass
- Maintain high protein intake of 1.6 grams per kilogram daily to support muscle protein synthesis
- Avoid aggressive caloric restriction, particularly without resistance training
- Measure body composition rather than body weight to track changes meaningfully