Which four factors determine your body's energy needs?

• A. Height, Diet, Sleep, and stress
• B. Activity level, Climate, Weight, and height
• C. Age, Body size, Body composition, and physical activity
• D. Gender, Muscle mass, BMI, and age

Answer: (C)

The main idea here is that your body's energy needs come from how much energy you burn at rest plus what you burn through activity. The four factors that determine this are age, body size, body composition, and physical activity.

Age matters because metabolic rate tends to slow with age as lean tissue declines and hormones shift, so energy requirements typically drop over time. Body size influences energy needs because a larger person has more tissue to sustain, including organs and muscles, which drives higher resting energy use. Body composition is key: lean mass such as muscle and organs uses more energy than fat tissue even at rest, so two people with the same weight but different proportions can have different energy needs. Physical activity directly boosts energy expenditure—the more you move, the more calories you burn beyond resting needs.

Other factors like gender, climate, or BMI can influence energy needs a bit, but they don’t determine them as directly or as strongly as the four listed.