Would It Work For Me? 5-HTP has been studied for over 30 years. One study compared overweight women who took 200 mg of 5-HTP before each meal to those who took a placebo. The women who took the supplement ate 1,084 fewer calories per day and felt less hungry during the day. Experts agree that 5-HTP works best for those who constantly crave food around the clock - especially carbs.