The New Weight Loss Revolution
A new class of drugs has been making headlines due to impressive results in helping people achieve significant weight loss. The drugs belong to a class know as Glucagon-like peptide-1 receptor agonists (GLP-1 RAs). These drugs were originally developed to treat type 2 diabetes mellitus (T2DM) and only later approved for weight loss in obesity management. These drugs mimic the action of the natural incretin hormone GLP-1, which is secreted by the gut in response to food intake. GLP-1 plays a critical role in regulating blood sugar and appetite by stimulating insulin secretion, inhibiting glucagon release, slowing gastric emptying, and promoting satiety [1] [2]. Currently, they are supplied as injectables in pen format and need to be administered for up to and over one year.
Mechanism of Action
GLP-1 Agonists
GLP-1 agonists mimic the natural hormone and bind to GLP-1 receptors and activate several metabolic pathways :
- Insulin secretion: They enhance glucose-dependent insulin release, helping to lower blood sugar levels.
- Glucagon suppression: They inhibit glucagon secretion, reducing hepatic glucose production.
- Delayed gastric emptying: This slows the absorption of nutrients, contributing to better glycemic control and increased satiety.
- Appetite regulation: GLP-1 agonists act on the hypothalamus to reduce hunger, leading to significant weight loss.
Saxenda – Daily injection (3.0 mg dose for weight loss) and Wegovy – Weekly injection (2.4 mg dose for weight loss) are approved for weight loss in the UK.
Dual GLP-1 / GIP Agonists
Mounjaro is a dual-agonist drug, meaning it activates two hormone pathways: GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). Thus in addition to the effects listed above for GLP-1 agonists, Mounjaro’s additional action (on GIP) further enhances appetite suppression, slows digestion, and improves how the body processes fats and sugars, potentially leading to greater weight loss . In a study which involved 751 obese individuals, and participants were given the highest tolerated dose of either Mounjaro or Wegovy, Mounjaro reduced weight by approximately 20%, while Wegovy reduced weight by roughly 14%.[6]
Mounjaro is licensed in the UK for the treatment of type 2 diabetes and was licensed for weight loss in November 2024.
Other Benefits of These Drugs
These drugs also have cardiovascular benefits, including reducing the risk of major adverse cardiovascular events (MACE), improving endothelial function, and lowering blood pressure. Additionally, they show potential in reducing the progression of chronic kidney disease (CKD) [1] [2].
Beyond diabetes and obesity, GLP-1 agonists are being investigated for other conditions, including non-alcoholic fatty liver disease (NAFLD), polycystic ovary syndrome (PCOS), and even substance use disorders. Their ability to cross the blood-brain barrier and influence the central nervous system has opened new avenues for treating neurodegenerative diseases and psychiatric disorders [2].
Economic Growth and Market Impact
The GLP-1 agonist market has experienced explosive growth, driven by their dual efficacy in managing diabetes and obesity, as well as their expanding indications. Drugs like Ozempic (semaglutide) and Mounjaro (tirzepatide, a dual GLP-1/GIP agonist) have become household names, with demand surging globally. See their explosive growth in prescribing in the UK on this website: weight-loss-drug-prescriptions
- Revenue Growth: The GLP-1 agonist global market is projected to exceed £40 billion annually by 2030, fuelled by increasing rates of obesity and diabetes worldwide. Semaglutide alone generated billions in revenue in 2023 (approx £15 billion) , with its weight-loss formulation, Wegovy, becoming a blockbuster drug.
- Obesity Treatment: The approval of GLP-1 agonists for obesity has significantly expanded their market. Obesity affects over 650 million adults globally, and GLP-1 drugs are among the most effective non-surgical treatments available, offering weight loss comparable to bariatric surgery in some cases [2].
- Cost and Accessibility: Despite their effectiveness, the high cost of GLP-1 agonists remains a barrier for many patients. For example, semaglutide can cost over $1,000 per month in the US without insurance, while the cost is limiting access in low- and middle-income countries.
GLP-1 agonists represent a groundbreaking advancement in the treatment of T2DM and obesity, with additional potential in other metabolic and neurological disorders. Their ability to address multiple health challenges has made them a cornerstone of modern pharmacotherapy. However, their high cost and limited accessibility remain challenges that need to be addressed to maximize their global impact.
Inappropriate Prescribing in the Community
It is not surprising considering the high cost of these drugs and the potential profits to be made from private clinics prescribing these drugs that there is growing evidence of abuse of the system by online pharmacies and by at least one well known high street pharmacy. Indeed, in February 2025 , the General Pharmaceutical Council (almost as a rebuke to the industry) introduced guidelines stating that online pharmacies must either see the patients in person on a video consultation with documented identity verification and or request GP records.
More recently, Channel 4’s Dispatches programme, Skinny Jab Scandal (2025-03-04), demonstrated that a 16-year-old girl was able to buy weight-loss drugs from a well known high street pharmacy twice, after ordering them online without age verification then collecting them in-store in person. In other cases presented by the programme, prescriptions for these drugs are being authorised by private clinics without proper verification checks.[3]
General Pharmaceutical Council Update (03-02-2025)
“The updated guidance emphasises that for high-risk medicines, the prescriber cannot base prescribing decisions on the information provided in an online questionnaire alone. Instead, the prescriber has to independently verify the information the person provides, either through timely two-way communication with the person, accessing the person’s clinical records, or contacting the person’s GP, their regular prescriber, or a third-party provider. This will help prevent people providing false information to obtain medicines that are not clinically appropriate for them.”
Potential Side Effects
There are a number of reported side effects for these drugs. Many of the side effects are relatively minor, however, some of the less common side effects can be severe and potentially life-threatening. A number of deaths have been reported, up to the end of Jan 2025, to The Medicines and Healthcare Products Regulatory Agency (MHRA) following the use of these GLP-1 agonists for both weight loss (22 deaths) and for the treatment of type 2 diabetes (60 deaths). The MHRA chief safety officer has stated, “The decision to start, continue, or stop treatments should be made jointly by patients and their doctor, based on full consideration of benefits and risks.”
Clearly prescribers need to ensure these drugs are issues to patients that satisfy the licensing conditions and that patients are monitored by appropriately by qualified and regulated healthcare professionals.
It is not this website’s responsibility to describe these in detail since accurate and up to date reporting is paramount as more details emerge. For details of potential side effects see official NHS websites for guidelines and details including but not restricted to those listed below.[4][5]
Appendix
The following is a list of GLP-1 agonists approved for T2DM and or weight management in the UK. There are several closely related analogues: Dulaglutide, Exenatide, Liraglutide, Lixisenatide, Semaglutide and Tirzepatide.
GLP-1 Agonists Licensed for Weight Loss in the UK
(Approved for obesity or overweight with weight-related comorbidities)
1. Liraglutide (Saxenda®) – Daily injection (3.0 mg dose for weight loss).
2. Semaglutide (Wegovy®) – Weekly injection (2.4 mg dose for weight loss).
GLP-1 Agonists Licensed for Type 2 Diabetes (T2DM) in the UK
Used for glycemic control, often with cardiovascular benefits.
- Dulaglutide (Trulicity®) – Weekly injection.
- Exenatide (Byetta®) – Twice-daily injection.
- Exenatide prolonged-release (Bydureon®) – Weekly injection.
- Liraglutide (Victoza®) – Daily injection (lower dose than Saxenda®).
- Lixisenatide (Lyxumia®) – Daily injection.
- Semaglutide (Ozempic®) – Weekly injection (lower dose than Wegovy®).
- Semaglutide (Rybelsus®) – Daily oral tablet (first oral GLP-1 agonist
Dual-Licensed GLP-1 Agonists (Weight Loss & T2DM in the UK)
These drugs are available in two different packages often one for T2DM and one for weight loss in order to differentiate their specific use.
- Semaglutide – Wegovy® (2.4 mg weekly) – Weight loss.
- Semaglutide – Ozempic® (0.5–1.0 mg weekly) – T2DM.
- Liraglutide – Saxenda® (3.0 mg daily) – Weight loss.
- Liraglutide – Victoza® (1.2–1.8 mg daily) – T2DM.
Dual GIP/GLP-1 Agonist Licensed for T2DM and Weight Loss in the UK
- Tirzepatide (Mounjaro®) (2.5 mg weekly )
Notes also:
- Ozempic® (a semaglutide 1.0 mg) is sometimes used off-label for weight loss but is only officially licensed for T2DM.
References
- Glucagon-Like Peptide-1 Receptor Agonists – StatPearls – NCBI Bookshelf.
https://www.ncbi.nlm.nih.gov/books/NBK551568/ - GLP-1 receptor agonist – Wikipedia.
https://en.wikipedia.org/wiki/GLP-1_receptor_agonist - Drug Selling Scandal References to Channel 4’s Skinny Jab Scandal (2025-03-04)
https://www.womenshealthmag.com/uk/health/a64013508/skinny-jab-scandal/
https://www.theguardian.com/tv-and-radio/2025/mar/04/tv-tonight-how-skinny-jabs-became-a-cultural-obsession - Safety Data
https://www.bmj.com/content/388/bmj.r390.full - General Pharmaceutical Council Update
https://www.pharmacyregulation.org/about-us/news-and-updates/online-pharmacies-strengthen-safeguards-prevent-unsafe-supply-medicines
https://assets.pharmacyregulation.org/files/2025-02/gphc-guidance-registered-pharmacies-providing-pharmacy-services-distance-february-2025.pdf - Tirzepatide as Compared with Semaglutide for the Treatment of Obesity
New England Journal of Medicine May 11, 2025