Final answer:
MET equations are based on the intensity of physical activity, and they measure the energy cost compared to the body at rest. They express activities in terms of multiples of the energy expenditure at rest (i.e., basal metabolic rate). Personal attributes like weight and age affect basal metabolic rate but not the MET value of an activity.
Step-by-step explanation:
Metabolic Equivalent Task (MET) equations are based on the intensity of physical activity, not on the weight of the individual, the time of day, or the individual's age. MET is a physiological measure expressing the energy cost of physical activities and is defined as the ratio of the metabolic rate (the rate of energy consumption) during a specific physical activity to a reference metabolic rate, set by convention to 3.5 ml O2 kg-1 min-1, which is equivalent to the amount of oxygen consumed while at rest in a seated position, known as the basal metabolic rate (BMR).
For instance, if an activity has a MET value of 5, that means it burns 5 times more calories than when the body is at rest. Although BMR varies with a person's age, gender, total body weight, and muscle mass, MET values focus on the activity level independent of these personal factors. An equation estimating the total daily energy expenditure would include the BMR and factors like the duration and intensity of different activities, measured in METs, performed throughout the day.