underweight
adj.having a weight that is lower than what is considered normal or healthy for your height. You might use this to describe a person or an animal that is too thin.
adj.having a weight below the standard or healthy level for a given height or age. Often used in medical contexts to describe nutritional status or in general conversation to describe physical appearance.
“The doctor told him he was underweight and needed to eat more.”
“The vet noted that the puppy was slightly underweight for its age and recommended a high-protein diet.”
“While the athlete's muscle mass was impressive, his overall body weight was considered underweight for his height, raising concerns about his long-term energy levels and recovery.”
“Only 6% of people with eating disorders are considered medically underweight.”