Semaglutide
Semaglutide (GLP-1 Receptor Agonist)
Semaglutide is a GLP-1 receptor agonist with 94% homology to human GLP-1. FDA-approved for type 2 diabetes (Ozempic) and chronic weight management (Wegovy), it represents the most clinically validated pharmacological weight loss intervention currently available. Weekly subcutaneous dosing and impressive efficacy data have made it the reference compound in metabolic peptide research.
Mechanism of Action
Semaglutide binds and activates GLP-1 receptors throughout the body with high affinity. In the pancreas, it stimulates glucose-dependent insulin secretion and suppresses glucagon release. These effects are glucose-dependent, meaning insulin release only increases when blood glucose is elevated — reducing hypoglycaemia risk compared to traditional insulin secretagogues.
Central nervous system GLP-1 receptors in the hypothalamus and brainstem mediate the powerful appetite-suppressing effects of semaglutide. Activation of these receptors reduces food intake by decreasing hunger signals, increasing satiety, and slowing gastric emptying — creating a sustained caloric deficit.
Semaglutide's extended half-life of approximately 7 days is achieved through C-18 fatty diacid attachment (allowing albumin binding) and two amino acid substitutions that resist DPP-4 degradation. This permits convenient once-weekly dosing.
Research Evidence
Semaglutide has one of the most robust clinical trial programmes of any peptide compound. The STEP trial series (for weight management) and SUSTAIN series (for diabetes) collectively enrolled tens of thousands of participants. The SURMOUNT and SELECT trials further established cardiovascular benefits.
STEP 1: Weekly Semaglutide in Adults with Overweight or Obesity
1,961 participants; 2.4mg weekly semaglutide produced mean 14.9% body weight reduction vs 2.4% with placebo over 68 weeks. 86% of semaglutide group achieved ≥5% weight loss.
SELECT: Semaglutide and Cardiovascular Outcomes
17,604 participants with overweight/obesity and established CVD; 2.4mg weekly semaglutide reduced major adverse cardiovascular events by 20% vs placebo — independent of glycaemic effects.
Typical Research Protocol
Standard titration: 0.25mg/week × 4 weeks → 0.5mg × 4 → 1.0mg × 4 → 1.7mg × 4 → 2.4mg maintenance. Slower titration reduces GI side effects.
Safety Profile
Reported Side Effects
- Nausea (44%)
- Diarrhoea (30%)
- Vomiting (24%)
- Constipation (24%)
- Injection site reaction
- Fatigue
Contraindications
- Personal/family history of medullary thyroid carcinoma
- Multiple endocrine neoplasia type 2 (MEN2)
- Pancreatitis history
- Pregnancy or breastfeeding
- Severe GI motility disorders
Common Research Stacks
Frequently Asked Questions
Is semaglutide FDA approved?
Yes. Semaglutide is FDA-approved as Ozempic (0.5–2.0mg weekly SC) for type 2 diabetes, Wegovy (2.4mg weekly SC) for chronic weight management in adults with BMI ≥30 or ≥27 with weight-related comorbidity, and Rybelsus (oral tablets) for type 2 diabetes.
How much weight can you lose on semaglutide?
In the STEP 1 trial (2.4mg/week), mean weight loss was 14.9% at 68 weeks. Approximately 32% of participants lost ≥20% of body weight. Results are significantly better when combined with a calorie-reduced diet and increased physical activity. Weight regain is common after discontinuation.
What is the difference between Ozempic, Wegovy, and Rybelsus?
All three contain semaglutide but differ in dose and indication. Ozempic (SC, up to 2mg weekly) is approved for type 2 diabetes. Wegovy (SC, 2.4mg weekly) is the higher-dose formulation approved for chronic weight management. Rybelsus (oral tablets, 7–14mg daily) is approved for type 2 diabetes — the only oral semaglutide form.
What happens when you stop semaglutide?
Weight regain is the primary concern after discontinuation. Extension data from STEP 1 showed participants regained roughly two-thirds of lost weight within one year of stopping, largely due to the return of appetite and hunger signals that semaglutide suppresses. Most clinical guidelines now classify obesity as a chronic disease requiring long-term or lifelong treatment.
Can semaglutide be used for PCOS or fertility?
Semaglutide is being actively researched for PCOS given the frequent comorbidity of insulin resistance and obesity in that condition. Some early data suggests weight loss from GLP-1 therapy improves hormonal markers and menstrual regularity in PCOS. However, semaglutide must be discontinued before attempting pregnancy due to lack of safety data in pregnancy.
Does semaglutide have cardiovascular benefits beyond weight loss?
Yes — the SELECT trial (17,604 non-diabetic participants with obesity and established CVD) showed semaglutide 2.4mg reduced major adverse cardiovascular events (MACE) by 20% versus placebo, independent of weight loss magnitude. This cardiovascular protection appears to involve direct anti-inflammatory and endothelial effects of GLP-1 receptor activation beyond metabolic improvements.
Key Research References
- Wilding JPH et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med.
- Lincoff AM et al. (2023). Semaglutide and cardiovascular outcomes in obesity without diabetes. N Engl J Med.
- Davies M et al. (2021). Semaglutide 2.4 mg once a week in adults with overweight or obesity. JAMA.
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