The arrival of GLP-1 receptor agonists as mainstream obesity treatments has redrawn the landscape of UK primary care. The evidence of cardiovascular benefit is striking, the weight loss unprecedented, and the demand overwhelming - but a 12-year NHS rollout plan, a surging black market, and data showing dramatic weight regain after stopping treatment are forcing clinicians and policymakers into deeply uncomfortable territory. For AKT candidates, this is one of the most pharmacologically and ethically layered topics in contemporary medicine.
A New Class Arrives in Primary Care
Glucagon-like peptide-1 receptor agonists are not new. Liraglutide and exenatide have been used in type 2 diabetes management for over a decade. What has changed is the scale of ambition: once-weekly subcutaneous semaglutide (Wegovy) and the dual GIP/GLP-1 agonist tirzepatide (Mounjaro) have now been approved not just for glycaemic control but for obesity management in people without diabetes at all. The therapeutic target has shifted from a complication to the condition itself.
NICE approved semaglutide for weight management in TA875 in 2023, followed by tirzepatide in TA1026 in December 2024. From 23 June 2025, integrated care boards across England have been required to facilitate the prescribing of tirzepatide in primary care for an eligible cohort of patients living with obesity, prioritised according to highest clinical need based on comorbidities and BMI. On the global stage, in December 2025, the World Health Organization issued a guideline making conditional recommendations for liraglutide, semaglutide and tirzepatide as long-term obesity treatments in adults, describing obesity as a chronic disease that can be treated with comprehensive and lifelong care.
This is a genuine paradigm shift. The framing of obesity as a chronic, relapsing, neurobiologically-driven condition - rather than a lifestyle choice amenable to advice and willpower - underpins the entire GLP-1 prescribing rationale. That framing is contested, and the contest matters clinically.
The Evidence That Changed Everything
The landmark trial establishing cardiovascular benefit beyond diabetes was SELECT, published in the New England Journal of Medicine in November 2023 by Lincoff and colleagues. In over 17,000 adults with pre-existing cardiovascular disease and overweight or obesity but without diabetes, once-weekly subcutaneous semaglutide at 2.4mg was associated with a 20% reduction in major adverse cardiovascular events - a composite of cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke - over a mean follow-up of nearly 40 months.
That finding is not straightforwardly explained by weight loss alone. A prespecified analysis of SELECT demonstrated that the cardiovascular benefits of semaglutide in people with overweight or obesity and pre-existing cardiovascular disease were independent of the magnitude of change in HbA1c, indicating that pleiotropic factors beyond glucose-lowering were driving the outcome. These likely include reductions in systemic inflammation, improvements in endothelial function, and direct effects on visceral adipose tissue. Importantly, previous weight-loss pharmacotherapies - sibutramine, rimonabant, lorcaserin - helped patients reduce body weight in high cardiovascular-risk populations but failed to improve cardiovascular outcomes, with some withdrawn due to serious adverse effects. The SELECT findings therefore represent genuinely novel territory: a weight-loss drug that actually reduces hard cardiovascular endpoints.
The weight-loss data are comparably impressive. The STEP 1 trial, published in the New England Journal of Medicine in 2021 by Wilding and colleagues, established that mean body weight change from baseline to week 68 was −14.9% with semaglutide compared with −2.4% with placebo, and 86.4% of participants receiving semaglutide achieved weight reductions of at least 5%. Tirzepatide, in the SURMOUNT-1 trial published in the New England Journal of Medicine in 2022, produced weight reductions up to 20% of starting body weight in clinical trial conditions. These numbers, long associated only with bariatric surgery, have prompted a fundamental reassessment of what pharmacotherapy can achieve.
The Problem: What Happens When You Stop
The clinical success of GLP-1 agonists has obscured a finding with profound implications for healthcare planning. The STEP 1 trial extension, published in Diabetes, Obesity and Metabolism in 2022 by Wilding and colleagues, followed participants for a year after stopping semaglutide. From week 0 to week 68, mean weight loss was 17.3% with semaglutide; following treatment withdrawal, participants regained 11.6 percentage points of lost weight by week 120, resulting in a net loss of only 5.6% from baseline, compared with 0.1% in the placebo group. Cardiometabolic improvements seen during treatment largely reverted towards baseline at week 120.
In plain terms: patients regained approximately two-thirds of their lost weight within a year of stopping treatment. The paper's own conclusion was unambiguous - findings confirm the chronicity of obesity and highlight the importance of maintaining long-term pharmacological treatment.
This creates a circular problem. If effective treatment requires indefinite continuation, yet NHS guidance imposes a two-year treatment cap for semaglutide in specialist settings, clinicians are placed in the position of offering a therapy they know will need to continue - in a system that cannot fund indefinite supply at scale. NICE's guidance executive accepted that a phased rollout was justified, and NHS England's funding variation request for tirzepatide was granted, resulting in a 12-year phased implementation rather than the default three months. The scale of eligible patients explains the caution: ICBs in England would have been required to meet the cost of treatment for an estimated 3.4 million people from March 2025.
The Postcode Lottery and the Parallel Market
As with so many NHS access issues, the gap between guideline approval and bedside availability is being filled - unevenly and sometimes dangerously - by the private sector. GP participants in a qualitative study published in the British Journal of General Practice in November 2025, conducted during a period when primary care integration for GLP-1 prescribing remained uncertain, expressed broadly positive views about the drugs but substantial hesitation about implementation. The reality at ICB level reflects this ambivalence: eligibility criteria vary between regions, waiting lists exist even within theoretically approved pathways, and some ICBs have moved faster than others.
The unregulated market this has created is alarming. There are documented cases of members of the public accessing semaglutide via Instagram, with at least one individual hospitalised after severe vomiting following a purchase through social media.The WHO guideline itself specifically flagged that the global demand for GLP-1 therapies has fuelled the spread of falsified and substandard products, threatening patient safety and trust, and underscoring the need for regulated distribution, prescription by qualified health professionals, and global cooperation. The MHRA has already issued alerts regarding counterfeit Ozempic and Saxenda injections found in the UK.
An Important Prescribing Consideration
For AKT candidates in particular, one pharmacological detail in this space demands attention: the interaction between tirzepatide and oral contraception. The College of Sexual and Reproductive Healthcare has advised that tirzepatide is currently the only GLP-1 receptor agonist found to reduce the effects of oral contraceptives, and that women of childbearing age using tirzepatide should be advised to switch to a non-oral contraceptive method or add a barrier method for four weeks after starting tirzepatide and for four weeks after any dose increase; no additional precautions are needed for non-oral contraceptives such as patches, rings and implants. This interaction, which does not apply to semaglutide or liraglutide, has obvious implications for prescribing and counselling in primary care - and is precisely the kind of mechanistically grounded, clinically applicable detail that features in AKT questions.
Medicalisation or Medicine?
The deeper controversy surrounding GLP-1 agonists is philosophical as much as pharmacological. Their effectiveness has accelerated a broader cultural question: should we treat obesity as we treat hypertension - as a chronic disease requiring indefinite pharmacological management - or does doing so risk pathologising normal human variation, undermining individual agency, and creating a generation of patients pharmacologically dependent on drugs manufactured by companies with obvious commercial interests?
These are not fringe concerns. Critics point to the industry funding behind most of the major trials, the commercial incentives to expand eligibility criteria, and the risk that a medicalised approach to obesity will crowd out attention to the structural, social and economic determinants of weight. Proponents respond that withholding effective treatment from people with a condition that shortens life expectancy by a decade on grounds of ideological purity is its own form of harm.
What is clear from the clinical data is that obesity meets every criterion of a chronic, relapsing disease with a biological substrate. The GLP-1 system is genuinely implicated in appetite regulation and energy homeostasis. The weight regain data following cessation do not reflect failure of willpower; they reflect the restoration of pre-treatment biological set-points. Understanding that framing is not just ethically important - it is the foundation of the clinical reasoning that should guide prescribing, counselling and follow-up.
What This Means for the AKT
The AKT tests applied pharmacological knowledge in realistic clinical contexts. The GLP-1 landscape is rich territory for this, and candidates should be confident across several domains: the mechanism of action of GLP-1 receptor agonists as incretin mimetics, the distinct dual-agonist profile of tirzepatide, the NICE eligibility criteria for semaglutide (TA875) and tirzepatide (TA1026) including BMI thresholds and the lower thresholds applied to South Asian, Chinese, Middle Eastern, Black African and African-Caribbean patients, the tirzepatide-oral contraceptive interaction, common adverse effects including nausea, diarrhoea and biliary disease, and the contraindications including personal or family history of medullary thyroid carcinoma or MEN2. The SELECT trial's finding of cardiovascular risk reduction independent of glycaemic change is the kind of nuanced clinical evidence that distinguishes good answers from excellent ones.
The GLP-1 revolution is not over. It has barely begun. Whether its promise is ultimately realised on an NHS scale - or whether resource constraints, equity failures and an unregulated parallel market define the coming decade - will depend in large part on the quality of clinical decision-making in primary care. That is precisely the kind of medicine the MLA is designed to test.