List out 5 most common conditions for underweight patient.
most common condition refers to MAX(COUNT(conditions.DESCRIPTION)); underweight patient refers to MIN(observations.VALUE WHERE observations.DESCRIPTION = 'Body Mass Index');
SELECT DISTINCT T2.DESCRIPTION, T2.VALUE, T2.UNITS FROM patients AS T1 INNER JOIN observations AS T2 ON T1.patient = T2.PATIENT WHERE T2.DESCRIPTION = 'Body Mass Index' GROUP BY T2.VALUE ORDER BY COUNT(T2.VALUE) LIMIT 5