According to WebMD, the most common prescription weight-loss drugs for women include orlistat, Belviq, Contrave, Saxenda, phentermine and Qsymia. Diet pills vary in efficacy from individual to individual.
Diet pills work in a variety of ways. Some, such as orlistat, prevent a body from digesting about a third of the fat consumed. Others, such as Belviq and phentermine, curb the appetite. Weight-loss pills are generally prescribed for individuals whose BMI is 30 or higher or who have conditions such as type 2 diabetes or high blood pressure. Common side effects of weight loss drugs include abdominal cramping, nausea, diarrhea and constipation.