What condition is characterized by an infant's inability to gain weight and has multiple causes?

The condition characterized by an infant's inability to gain weight, with multiple causes, is failure to thrive. This term encompasses a broad range of situations where an infant's physical growth is significantly below the expected norms for their age and sex. The causes of failure to thrive can be multifaceted, including inadequate caloric intake due to feeding difficulties, neglect, or improper breastfeeding practices. Additionally, underlying medical conditions such as gastrointestinal disorders, metabolic issues, or even chronic infections can contribute to this condition.

While malnutrition could be related to failure to thrive, it often refers more specifically to a lack of nutrients, whereas failure to thrive is a broader diagnosis that includes not only nutritional deficiencies but also factors affecting growth and overall health. Obesity would involve an excess of weight, which is the opposite of what is observed in failure to thrive. Overfeeding could theoretically contribute to weight gain, but in the context of failure to thrive, it is more about insufficient caloric intake relative to the infant’s needs rather than excessive feeding. Therefore, failure to thrive is the most accurate term to describe the condition in question.