Which of these affect the number of kilocalories you need every day?

The daily calorie needs of an individual are influenced by a variety of factors, and all the factors listed play a significant role in determining overall caloric requirements.

Physical activity directly impacts caloric expenditure. The more active an individual is, the more energy they will burn, thereby increasing their daily caloric needs. For instance, someone who engages in regular exercise or has a physically demanding job will require more kilocalories compared to someone who leads a sedentary lifestyle.

Body composition is another critical factor. Muscle tissue is more metabolically active than fat tissue, meaning that individuals with higher muscle mass typically require more kilocalories to maintain their weight compared to those with a higher percentage of body fat. Therefore, a person’s mix of lean mass versus fat mass can significantly influence their energy needs.

Age also affects caloric requirements as metabolic rates tend to decrease with age. Younger individuals typically have higher energy needs due to higher levels of physical activity and a faster metabolic rate, while older adults may require fewer calories as their activity levels decrease and metabolism slows down.

Considering that each of these elements—physical activity, body composition, and age—contributes substantially to the overall calculation of energy expenditure, it follows that the most accurate answer encompasses all these factors together.