What physiological metric is measured in ml/kg and indicates energy expenditure?

The correct answer is Metabolic Equivalent (MET), as it is a unit that indicates the energy expenditure of an individual relative to their body weight. Specifically, MET is defined as the ratio of the metabolic rate during a physical activity to the resting metabolic rate and is expressed in milliliters of oxygen consumed per kilogram of body weight per minute (ml/kg/min). This measurement allows trainers and health professionals to assess the intensity of various activities and understand the energy cost associated with them in relation to a person's weight.

Caloric intake does not use ml/kg as a measurement and instead is expressed in calories, so it does not fit the parameters of the question. Body mass index (BMI) is a measure of body fat based on height and weight, and while it is useful for categorizing weight status, it does not directly correlate with energy expenditure. Blood glucose levels, typically measured in mg/dL, indicate sugar levels in the blood but do not reflect energy expenditure or metabolic rates in the context of the question.