Which of the following is a factor that affects basal metabolic rate?

• A. Size, age, and skin color.
• B. Dietary fat intake.
• C. Size, sex, body composition, age, thyroid hormone.
• D. Exercise frequency.

Answer: (C)

Basal metabolic rate is the energy the body needs at rest to support essential functions, and it is shaped by factors that reflect the size of the body, the amount of metabolically active tissue, and hormonal influences. Larger bodies require more energy to maintain basic processes, and lean (muscle and organ) tissue is more metabolically active than fat, so greater lean mass raises BMR. Sex differences come from typical variations in lean mass and hormones between males and females, influencing the baseline rate. As we age, BMR tends to decline because lean mass often decreases and hormonal changes alter metabolic activity. Thyroid hormone directly stimulates many metabolic pathways, boosting the rate at which cells use energy; higher thyroid activity raises BMR.

Dietary fat intake doesn't significantly alter the resting energy requirement once meals are balanced, and exercise frequency affects total energy expenditure more than the resting rate itself. Skin color has no meaningful impact on basal metabolic rate.