5-HTP Diet: Does It Do the job?
On the subject of actual research on 5-HTP and its influence on weight loss, you won't find much. In one small study, Italian researchers put a group of obese, hyperphagic (science for "eating too much") adults on a 1,200-calorie diet and provided half of them 300 milligrams of 5-HTP to take 30 minutes before each meal. After 12 weeks, these participants lost about 7.2 pounds compared to 4 pounds for the rest of the group, who, unknowingly, took a placebo.
What's key to note is that while the weight loss for the placebo group wasn't statistically considerable, during the second half of the study, all participants were provided particular support to reduce their calorie intake. The sugar-pill group missed the calorie mark by almost 800 calories. To me this seems more like not following directions than the impact of a supplement.
And while it appears the 5-HTP might have assisted with weight loss, for someone who is extremely overweight to lose 7 pounds in 12 weeks while also eating an extremely calorie-restricted diet isn't that remarkable.
Outside of this study, there is not a lot more-- aside from hypotheses and biochemical mechanisms-- to show that 5-HTP is a hunger suppressant. If you are exercising routinely and following a calorie- and carbohydrate-restricted diet plan, then I would have a hard time seeing an advantage to supplementing with 5-HTP.
If you're still interested in taking 5-HTP, know that it's easily marketed as relatively safe and side-effect free, but anyone taking antidepressants, which can sadly help in weight gain, should prevent taking the supplement, as it can mess with the result and required dose of serotonin in antidepressants.