5-HTP, Appetite and Binge Eating

With all the excitement over weight-loss medications like Ozempic and Mounjaro, it’s become increasingly obvious that there are important biochemical mechanisms that influence appetite. These medications work by stimulating the glucagon-like peptide-1 (GLP-1) pathway. GLP-1 is a hormone produced by the intestinal tract after eating a meal. The hormone helps increase insulin production while affecting appetite centers in the brain, decreasing hunger and producing a sense of fullness. This effectively decreases food intake leading to significant weight loss.

The powerful effects of these medications highlight how hormonal and biochemical pathways affect eating behaviors. And while GLP-1 medications have notable effects, there are other important pathways that also influence eating. These other pathways can be critical when considering patients struggling with overeating and binge eating disorder (BED). And one of the more critical biochemical pathways involves serotonin.

Serotonin and Appetite

While usually considered a feel-good neurotransmitter relevant for depression treatment, serotonin has other roles in the body. For decades, serotonin has been linked to appetite and food intake (Tecott 2007). Similar to GLP-1, in certain parts of the brain, serotonin acts to decrease appetite and enhance a sense of fullness. Historically, a number of obesity medications have focused on this mechanism, including fenfluramine and lorcaserin. However, due to unrelated cardiovascular concerns with fenfluramine and increased cancer risk with lorcaserin, these medications are no longer approved for obesity treatment.

A simpler and safer approach is simply to increase serotonin production through the use of its precursor: 5-hydroxytryptophan (5-HTP). For patients struggling with overeating and binging, treatment with 5-HTP can help.

5-HTP, Satiety and Weight Loss

One of the more impressive studies on 5-HTP and weight loss utilized a high dose of 5-HTP, 900 mg as compared to placebo (Cangiano 1992). In the study, subjects were treated for six weeks before any dietary recommendations were given. Then they were followed for another six weeks after being given a weight-loss diet. Subjects on 5-HTP lost 3.7 pounds in the first six weeks, followed by another 7.3 pounds while on the six-week weight-loss diet.

A separate trial in obese women using 8 mg of 5-HTP per kilogram of body weight also found weight loss over the course of five weeks (Ceci 1989). The women found that their appetite was reduced and food intake decreased. Weight loss averaged just over 3 pounds during the five-week trial.

In patients with type 2 diabetes, 5-HTP was prescribed at 750 mg per day or placebo for two weeks (Cangiano 1998). While the placebo did not affect weight, patients on 5-HTP lost 4.6 pounds and consumed significantly less carbohydrates and fat.

Used as a sublingual, an herbal combination product that has high levels of 5-HTP was given to overweight women (Rondanelli 2009). The product was found to reduce appetite and facilitate weight loss with a reduction in both body mass index and measured skin-fold thickness.

Mechanisms of 5-HTP

As a supplement, 5-HTP may help in a number of ways. The data from the human studies already cited appear to indicate an increase in fullness or satiety with its use. A study using functional magnetic resonance imaging (fMRI) of the brain found that 5-HTP activated brain areas that encourage a healthy body weight and increased preferences towards protein-rich foods and away from carbohydrate and high-calorie options (Ioannou 2016).

Interestingly, a study in physically fit men and women found that a dose of just 100 mg of 5-HTP was enough to decrease body fat mass (Evans 2023). In the study, participants were explicitly instructed to not decrease their food intake which was tracked through a mobile app. Subjects on 5-HTP lost around 1.8 pounds of fat whereas those on placebo had a small gain, all without major changes in food intake. Beyond its effects for reducing appetite, these results suggest that 5-HTP may also help to alter body composition in a beneficial manner.

Takeaway

There are a number of different biochemical and hormonal pathways in the human body involved with appetite, eating behaviors and weight gain. Individuals who are struggling with overeating often have disturbances in these pathways.

By properly targeting these hormonal and neurotransmitter systems, including serotonin, it is often possible to get to the root of the dysregulation causing the problems around food intake. When the underlying factors are addressed appropriately, recovery and relief become attainable goals.