What is a GLP-1 medicine? The hormone system behind the headlines

The hormone you already have #

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases within minutes of eating. The hormone tells your brain you are full, slows the stomach so food leaves gradually, and prompts insulin release when blood sugar rises. The hormone is one of the body's core appetite-regulation signals.

Natural GLP-1 lasts only minutes before enzymes break the hormone down. The medicines are engineered versions which last days or a week. They send the same signal for longer.

The medicine family #

• Semaglutide (Wegovy, Wegovy tablets), pure GLP-1 mimic, weekly injection or daily tablet.
• Tirzepatide (Mounjaro), mimics GLP-1 and a second gut hormone, GIP, which appears to deepen the effect.
• Orforglipron (Foundayo), a small-molecule GLP-1 agonist which survives digestion as an ordinary tablet.
• Liraglutide (Nevolat, formerly Saxenda), the first-generation daily injection.

Why they quieten 'food noise' #

People with obesity often describe constant background thoughts about food: planning, craving, resisting. GLP-1 signalling acts directly on appetite centres in the brain, and patients almost universally report this noise turning down. Appetite is substantially hormonal, not a character trait. This finding is the real change these medicines represent.

What they do not do #

• They do not burn fat directly. They make eating less feel natural.
• They do not choose what you eat, protein and nutrition still need attention.
• They do not retrain habits by themselves, which is why maintenance planning matters.
• They are not suitable for everyone, eligibility rules exist for real safety reasons.

A short history #

GLP-1 medicines have treated type 2 diabetes since 2005. Weight loss was a consistent side effect, which led to obesity-specific trials and licences: liraglutide in 2015, semaglutide in 2021, tirzepatide in 2023, and the first tablets after. Two decades of safety data underpin today's prescriptions.