Below what BMI is someone considered underweight?

A Body Mass Index (BMI) of less than 18.5 indicates that an individual is considered underweight according to the World Health Organization classifications. This BMI threshold is widely recognized in public health guidelines, as it reflects a weight that is significantly below the average healthy weight for a given height.

Individuals with a BMI below this level may be at risk for various health issues related to insufficient body weight, such as nutrient deficiencies, weakened immune function, and potential complications with physical and mental health. Understanding BMI categories is crucial in sports nutrition as it can help assess body composition and inform dietary and lifestyle recommendations for optimal health and performance.

Values above 18.5 correspond to healthy, overweight, and obesity categories, thus clarifying that only a BMI below this threshold qualifies as underweight.