If a person has a body mass index lower than 18.5, this could indicate they are underweight enough to be malnourished. Malnutrition is associated with various health problems. Some people with a low BMI may lack vital vitamins and minerals, which often eads to deficiencies. Certain factors can raise one's risk of having a low BMI, including low immunity, respiratory and digestive diseases, some cancers, and osteoporosis (weakened bones).

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