Phenylpropylamine is similar in structure to amphetamine and ephedrine and may act as an appetite suppressant to induce weight loss. It is believed to act via the alpha-1 adrenergic receptor . Five RCTs (published between 1982 and 1999) investigated it. Only one trial was categorized as having a low degree of bias for all categories. All studies were published in the United States; three were industry funded (two not reported), and the number of participants ranged from 7 to 51. Study duration ranged from 6 to 12 weeks. The ages of participants ranged from 18 to 65 years. The number of women ranged from 56% to 100%, with one study not reporting sex composition. Only one study did not report the differences at follow-up between both arms. Three studies demonstrated significant differences between arms, and the remaining did not report on significance. Best Healthiest Fat Burner Supplement: Top 7 The one high-quality study (low risk of bias) did not demonstrate significant changes in weight between groups at follow-up .