What defines underweight in nutritional disorders?

Underweight in nutritional disorders is specifically defined as having a weight that is less than the established standards for age and sex. This definition is based on growth charts and standards that provide a benchmark for health professionals to assess an individual's weight relative to their age and gender. It indicates that the person's body weight is insufficient for their height, which can lead to various health issues and nutritional deficiencies.

Understanding this definition is crucial as it helps in identifying individuals who may be at risk for health problems due to inadequate body mass. While factors such as calorie intake, height, and protein consumption are important in assessing overall nutritional status, the defining characteristic of being underweight is primarily linked to the comparison of actual body weight against standardized metrics for growth and development.