GLP-1 Drugs Explained

GLP-1 receptor agonists act on the gut–brain axis to reduce hunger and improve how the body handles food energy. By enhancing insulin secretion and slowing stomach emptying, they promote steadier blood sugar levels and reduce calorie intake and cravings.

Clinical trials have shown that GLP-1 drugs such as semaglutide and liraglutide, and newer dual-action agents like tirzepatide, can lead to average weight reductions of 10–22% when combined with lifestyle support.

GLP-1 is a natural hormone made in the small intestine after eating. It tells your brain and pancreas that you’ve eaten enough and helps keep blood sugar stable.

GLP-1 is released from cells in the gut. It:

• Stimulates insulin release when blood sugar is high.
• Suppresses glucagon, which would otherwise raise blood sugar.
• Slows how quickly food moves through the stomach.
• Sends satiety signals to the brain, reducing appetite and cravings.

Several GLP-1 drugs are available, each with different doses, timing, and brand names.

Liraglutide

• Brand examples: Saxenda, Victoza
• Frequency: Daily
• Main indication: Weight loss and type 2 diabetes

Semaglutide

• Brand examples: Wegovy, Ozempic, Rybelsus (oral)
• Frequency: Weekly or daily (depending on the formulation)
• Main indication: Weight loss and diabetes

Tirzepatide

• Brand examples: Mounjaro
• Frequency: Weekly
• Main indication: Dual GIP/GLP-1 therapy for weight loss and diabetes

Exenatide / Dulaglutide

• Brand examples: Byetta, Trulicity
• Frequency: Daily or weekly
• Main indication: Type 2 diabetes (not primarily for weight loss)

All of these target the same GLP-1 pathway, though potency and tolerability vary.

These medicines reduce hunger, increase feelings of fullness, and make it easier to eat less.GLP-1 drugs act on appetite control centres in the brain (especially the hypothalamus) and on the stomach to delay emptying.

This dual effect:

• Reduces total calorie intake.
• Lowers cravings for high-calorie foods.
• Helps people maintain a calorie deficit without strong hunger.

GLP-1 drugs do more than help with weight loss: they also improve blood sugar, heart health, and overall metabolic function.

Clinical evidence shows GLP-1 medicines can:

• Reduce HbA1c and fasting glucose.
• Lower blood pressure and cholesterol.
• Reduce the risk of major heart events in people with diabetes.
• Support improvements in liver health and inflammation markers.

GLP-1 medications have well-defined safety profiles based on extensive clinical research. Most effects relate to how these drugs slow digestion and interact with the body’s natural hormone pathways. Common experiences in studies include temporary nausea, changes in appetite, and mild gastrointestinal symptoms as the body adjusts.

Researchers also monitor how GLP-1 medications affect long-term metabolic health, cardiovascular outcomes, and liver markers. These findings help clinicians understand how the drugs behave in different populations and how the body adapts over time.

Because GLP-1 drugs influence digestion and blood sugar regulation, ongoing scientific monitoring focuses on areas such as:

• how the gut responds to slower gastric emptying
• how appetite signals change over time
• the balance between blood glucose regulation and insulin response
• the relationship between dosage, tolerability and metabolic effects

• Wilding JPH et al. N Engl J Med 2021 (STEP 1)
• Jastreboff AM et al. N Engl J Med 2022 (SURMOUNT-1)
• Pi-Sunyer X et al. N Engl J Med 2015 (SCALE)
• Marso SP et al. N Engl J Med 2016 (SUSTAIN-6)
• NICE NG248 (2023); TA875 (2023)
• EMA EPARs for Wegovy, Mounjaro, Saxenda, Rybelsus

Dr Adam Abbs is a GP and Medical Lead for Europe and UK for biomarker company Hurdle. An NHS-trained GP, he graduated from Hull York Medical School in 2010 with an MBBS, then worked across a range of specialties in Newcastle and Manchester. Dr Adam Abbs is SCOPE certified (the international gold standard for obesity management) and has a keen focus on personalised medicine and weight loss. He authored Medicspot’s Behaviour Change Course.

Dr Abby Hyams completed her medical training in Bristol and has been a GP for 19 years, spending many of those as a partner in an NHS practice in Hemel Hempstead. She has a particular passion for supporting patients with weight loss and promoting positive behaviour change, helping individuals build sustainable habits that improve their long-term health and wellbeing.

This article is for general information only and should not be used for the diagnosis or treatment of medical conditions. Medic Spot Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. In the event of an emergency, please call 999 for immediate assistance.

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