Which body composition component is the principal contributor to resting energy expenditure?

Which body composition component is the principal contributor to resting energy expenditure?

• A. Lean body mass
• B. Fat mass
• C. Body weight
• D. Skeletal muscle mass

Answer: (A)

Resting energy expenditure is driven largely by lean body mass. The tissues that are metabolically active at rest—especially organ systems such as the liver, brain, heart, and kidneys—require substantial energy per unit of mass. While skeletal muscle is part of lean mass and contributes to energy use, the overall energy demand of these organs and other lean tissues makes lean body mass the strongest predictor of REE. Fat mass, in contrast, has a much smaller metabolic rate per kilogram, so changes in fat mass have a lesser impact on resting energy needs. In practice, increasing lean mass tends to raise REE modestly, whereas adjustments in fat mass alone influence REE to a smaller extent.

Resting energy expenditure is driven largely by lean body mass. The tissues that are metabolically active at rest—especially organ systems such as the liver, brain, heart, and kidneys—require substantial energy per unit of mass. While skeletal muscle is part of lean mass and contributes to energy use, the overall energy demand of these organs and other lean tissues makes lean body mass the strongest predictor of REE. Fat mass, in contrast, has a much smaller metabolic rate per kilogram, so changes in fat mass have a lesser impact on resting energy needs. In practice, increasing lean mass tends to raise REE modestly, whereas adjustments in fat mass alone influence REE to a smaller extent.