Which of the following factors decreases BMR?

Which of the following factors decreases BMR?

• A. Aging, fasting, sleep
• B. Growth, infection
• C. Fever, elevated hormones
• D. Exercise

Answer: (A)

Basal metabolic rate is the amount of energy the body requires at rest to maintain essential functions. It can be lowered when the body’s energy demands at rest decline. Aging leads to loss of lean muscle mass and hormonal changes that reduce energy needs, so BMR tends to decrease with age. Fasting signals the body to conserve energy, lowering thyroid activity and overall metabolic rate to preserve resources. Sleep reduces physiological activity—lower heart rate, brain activity, and thermogenesis—so energy expenditure at rest drops further. In contrast, states that raise energy needs do so: growth and infection increase demand for energy to build tissues and fuel immune responses; fever and elevated hormones push metabolism higher; and exercise raises energy use and can elevate BMR afterward. So the factor that decreases BMR among the options is aging, fasting, and sleep.

Basal metabolic rate is the amount of energy the body requires at rest to maintain essential functions. It can be lowered when the body’s energy demands at rest decline. Aging leads to loss of lean muscle mass and hormonal changes that reduce energy needs, so BMR tends to decrease with age. Fasting signals the body to conserve energy, lowering thyroid activity and overall metabolic rate to preserve resources. Sleep reduces physiological activity—lower heart rate, brain activity, and thermogenesis—so energy expenditure at rest drops further.

In contrast, states that raise energy needs do so: growth and infection increase demand for energy to build tissues and fuel immune responses; fever and elevated hormones push metabolism higher; and exercise raises energy use and can elevate BMR afterward. So the factor that decreases BMR among the options is aging, fasting, and sleep.