Medical therapy for obesity

Indications

GLP-1 is a receptor that stimulates glucose-dependent insulin release, and inhibits glucagon release and gastric emptying, and act directly in the hypothalamus to decrease hunger

Incretin-based therapies (GLP-1 and GIP, essentially; gut hormones that respond to nutrient intake)
- GLP-1 agonists
  - Semaglutide (Ozempic in low dose, Wegovy in high dose)
    - As of March 2025, only on PBS for T2DM, and recommended not to use off-label due to global shortages
    - Weekly subcutaneous injection
    - GIT side effects - delayed gastric emptying, gastritis, abdominal pain
    - Particularly good for diabetics
    - Need to continue for over a year for best results
    - Weight will go back on after stopping, but not straight away
  - Liraglutide
    - Daily subcutaneous injection
- GIP agonists
  - Tirzepatide (Mounjaro) - GIP and GLP-1 agonist
  - Theoretically better, but not tested head-to-head yet
- Contraindications:
  - Personal or family history of medullary thyroid cancer of MEN2 - possible increased risk
  - Pregnancy
- Adverse effects:
  - Nausea 25-40%
  - Vomiting, diarrhoea or constipation 10-20%
  - Gastroparesis
  - Pancreatitis (likely just microlithiasis)
- Strategies to mitigate risks:
  - Smaller, more frequent meals
  - Eating slowly
  - Limiting fatty meals
Old options
- Phentermine + extended-release topiramate
- Bupropion-naltrexone
- Orlistat
- Phentermine