Doctor's Answers (1)
There is no hard and fast rule for this. It is generally prescribed as an adjunct to diet and exercise in suitable individuals. If the BMI is very high (>30 kg/m2 or >27 kg/m2 with other risk factors like diabetes, high cholesterol, high blood pressure) then the benefits of treatment may outweigh the risks.
This is generally a short term measure. If an individual's BMI is not that high but has other complications of weight gain (physical/psychological), and treatable causes of weight gain have been excluded, then a short course of this may be considered.
Although rare, the effect on the heart (can cause palpitations or increased heart rate, acquired problems with the heart valve or pulmonary hypertension) is a significant potential adverse effect, hence this is not prescribed on a long term basis.