Peptides themselves do not directly cause weight loss, though certain types may aid in weight management by regulating metabolism. While marketing for "weight-loss peptides" often highlights benefits such as promoting fat breakdown and suppressing appetite, their actual efficacy depends on specific ingredients, dosage, and individual physiology.

From a medical perspective, certain bioactive peptides-such as glucagon-like peptide-1 (GLP-1) analogs-are indeed used to treat obesity; these drugs function by delaying gastric emptying and increasing satiety, but they are prescription medications rather than standard dietary supplements. Conversely, there is currently insufficient clinical evidence to support the weight-loss claims of dietary supplements like collagen peptides or soy peptides; while some products may indirectly support metabolism through nutritional supplementation, they cannot replace dietary control and exercise.