What typical body composition change accompanies aging, contributing to lower energy-related requirements?

What typical body composition change accompanies aging, contributing to lower energy-related requirements?

• A. Increased fat mass and decreased lean mass
• B. Decreased fat mass and increased lean mass
• C. Increased fat mass and increased lean mass
• D. Decreased fat mass and decreased lean mass

Answer: (A)

As people age, the body loses muscle mass (sarcopenia) and tends to gain fat mass, so fat mass increases while lean mass decreases. Lean tissue, especially skeletal muscle, is highly metabolically active and largely drives resting energy expenditure. When lean mass shrinks, the resting energy needs drop, even if total body weight stays the same or increases due to more fat. This combination—more fat and less muscle—explains why energy-related requirements typically decline with aging. Other patterns, like losing fat while gaining muscle, would raise energy needs, or decreasing both components would reflect a different, less typical aging trajectory.

As people age, the body loses muscle mass (sarcopenia) and tends to gain fat mass, so fat mass increases while lean mass decreases. Lean tissue, especially skeletal muscle, is highly metabolically active and largely drives resting energy expenditure. When lean mass shrinks, the resting energy needs drop, even if total body weight stays the same or increases due to more fat. This combination—more fat and less muscle—explains why energy-related requirements typically decline with aging. Other patterns, like losing fat while gaining muscle, would raise energy needs, or decreasing both components would reflect a different, less typical aging trajectory.