Semaglutide

Mechanism of action

Semaglutide activates the GLP-1 receptor, a G protein-coupled receptor expressed in the pancreas, gastrointestinal tract, and central nervous system. The main effects include: (1) increased glucose-dependent insulin secretion and reduced glucagon secretion under hyperglycemic conditions; (2) slowing of gastric emptying (especially in the initial phases), with a reduction in postprandial glycemic spikes; (3) central modulation of satiety and food reward, with reduced appetite and energy intake; (4) indirect cardiometabolic effects mediated by weight loss, improved glycemic control, and possible actions on inflammation and endothelial function. The prolonged half-life derives from structural modifications that increase albumin binding and reduce enzymatic degradation.

Supported benefits

• Reduction in HbA1c and improvement in glycemic control in type 2 diabetes mellitus (strong)
• Clinically significant weight loss in people with obesity/overweight (in the context of lifestyle interventions) (strong)
• Reduction in the risk of major cardiovascular events in selected high-risk populations (composite endpoints in cardiovascular trials) (strong)
• Improvement in some cardiometabolic risk factors (blood pressure, triglycerides, markers of hepatic steatosis in some studies) (moderate)
• Improvement in quality of life and parameters related to eating behavior (hunger/cravings) in some studies (moderate)

Safety & side effects

• Gastrointestinal: nausea, vomiting, diarrhea, constipation, dyspepsia, abdominal pain (among the most common; often dose-dependent and more frequent during the titration phase)
• Reduced appetite and possible aversion to certain foods
• Reflux/belching, feeling of early fullness
• Headache, fatigue (in some individuals)
• Injection-site reactions (subcutaneous formulation)
• Increased risk of cholelithiasis/cholecystitis, partly associated with rapid weight loss
• Pancreatitis: a rare but clinically relevant event; requires medical evaluation if compatible symptoms occur
• Worsening or onset of diabetic retinopathy in some contexts, especially with rapid glycemic improvement in subjects with pre-existing retinopathy
• Dehydration and electrolyte disturbances secondary to vomiting/diarrhea, with possible impact on renal function (especially in vulnerable individuals)

FAQ

Is it a supplement or a “performance” peptide?

No. It is a peptide drug (GLP-1 agonist) developed and studied for clinical indications (type 2 diabetes and, under specific conditions, weight management). It is not intended as an ergogenic aid and may have adverse effects that worsen training (nausea, reduced energy intake).

Why does it cause weight loss?

It primarily reduces appetite and increases satiety through central actions, and it may slow gastric emptying, reducing caloric intake. Weight loss is more substantial when combined with lifestyle interventions.

What are the most common side effects?

Gastrointestinal disturbances (nausea, vomiting, diarrhea or constipation, dyspepsia) and reduced appetite. They are generally more frequent at the beginning or during dose increases in clinical protocols.

Is there a risk of hypoglycemia?

On its own, the risk is relatively low because the insulinotropic effect is glucose-dependent, but the risk increases if combined with insulin or sulfonylureas. Management requires clinical supervision.

Is it true that it can increase the risk of gallbladder problems?

Yes, an increase in biliary events (e.g., gallstones) has been observed in some studies, probably also linked to rapid weight loss. It is a risk that should be considered and monitored clinically.

What does the warning about medullary thyroid carcinoma mean?

For the GLP-1RA class, there are warnings/contraindications in subjects with a personal or family history of MTC or MEN2, based on preclinical data and regulatory assessments. The relevance for humans should be discussed with a physician, but the contraindication is reported on several labels.