GLP-1 receptor agonists have gained considerable attention for their role in weight management, prompting questions about their effects on abdominal fat. Whilst these medications do not selectively 'burn' belly fat through direct mechanisms, clinical evidence demonstrates they promote significant overall weight loss, including reductions in visceral adipose tissue—the metabolically harmful fat surrounding internal organs. Understanding how GLP-1 medications work, what realistic outcomes to expect, and who may be suitable for treatment is essential for informed decision-making. This article examines the evidence on GLP-1 medications and body fat distribution, drawing on UK clinical guidance and regulatory frameworks.

What Are GLP-1 Medications and How Do They Work?

Glucagon-like peptide-1 (GLP-1) receptor agonists are a class of medications originally developed for type 2 diabetes management but now also licensed for weight management. These injectable medicines mimic the action of naturally occurring GLP-1, a hormone produced in the intestine following food intake.

The mechanism of action involves several physiological pathways. GLP-1 medications bind to GLP-1 receptors in the pancreas, stimulating insulin secretion when blood glucose levels are elevated whilst simultaneously suppressing glucagon release. Crucially for weight management, these drugs act on receptors in the brain—particularly in the hypothalamus and brainstem—to reduce appetite and increase feelings of satiety. They also slow gastric emptying, meaning food remains in the stomach longer, contributing to prolonged fullness after meals, though this effect may attenuate over time.

Currently available GLP-1 medications in the UK include:

• Semaglutide (Ozempic for diabetes only; Wegovy specifically licensed for weight management)

• Liraglutide (Victoza for diabetes only; Saxenda specifically licensed for weight management)

• Dulaglutide (Trulicity, licensed only for diabetes, not weight management)

• Tirzepatide (Mounjaro), a dual GLP-1 and GIP receptor agonist licensed for type 2 diabetes

These medications are administered via subcutaneous injection, typically weekly or daily depending on the specific formulation. It's important to note that Ozempic (semaglutide 0.25-1mg) should not be used off-label for weight loss, particularly given NHS/MHRA supply prioritisation for people with diabetes.

The delayed gastric emptying effect may reduce the absorption of some oral medicines. Patients should consult their healthcare provider or refer to the medicine's patient information leaflet for specific guidance on managing potential interactions.

Evidence on GLP-1 and Body Fat Distribution

The question of whether GLP-1 medications specifically 'burn' belly fat requires careful consideration of the available evidence. GLP-1 drugs do not selectively target abdominal fat through direct fat-burning mechanisms; rather, they promote generalised weight loss through reduced energy intake and metabolic changes. However, clinical studies have demonstrated that the weight lost with GLP-1 treatment includes significant reductions in visceral adipose tissue—the metabolically active fat surrounding internal organs in the abdominal cavity.

Clinical trials using imaging techniques such as MRI and CT scans have shown that GLP-1 receptor agonists lead to reductions in both subcutaneous fat (beneath the skin) and visceral fat. Research from the STEP programme (semaglutide), SCALE studies (liraglutide), and SURMOUNT trials (tirzepatide) consistently demonstrates significant reductions in waist circumference, which correlates with abdominal fat loss. These studies suggest that visceral fat may decrease proportionally during GLP-1-induced weight loss, similar to patterns seen with dietary caloric restriction.

Key findings from clinical trials include:

• Reductions in waist circumference, an indirect marker of abdominal fat

• Improvements in metabolic markers associated with visceral adiposity (HbA1c, lipid profiles, liver enzymes)

• Decreased hepatic fat content in patients with fatty liver disease

It is important to understand that GLP-1 medications do not 'burn' fat through thermogenesis or direct lipolysis. Instead, they create a sustained caloric deficit by reducing appetite and food intake, leading to mobilisation of fat stores throughout the body. The apparent benefit for abdominal fat reflects the body's natural pattern of fat loss during caloric restriction, where visceral fat often responds favourably to weight reduction interventions.

What to Expect: Weight Loss Results with GLP-1

Weight loss outcomes with GLP-1 medications vary considerably depending on the specific agent used, dosage, treatment duration, and individual patient factors. Clinical trial data provides useful benchmarks, though real-world results may differ.

In the STEP clinical trials, semaglutide 2.4 mg (Wegovy) demonstrated average weight loss of approximately 15% of initial body weight over 68 weeks when combined with lifestyle interventions. The SCALE programme showed liraglutide 3.0 mg (Saxenda) typically produces weight loss of around 8-10% over one year. In the SURMOUNT-1 trial, tirzepatide demonstrated even more substantial results, with some participants losing over 20% of their starting weight.

Weight loss typically follows a predictable pattern:

• Initial phase (0-3 months): Gradual dose escalation with modest weight reduction as appetite suppression begins

• Active loss phase (3-12 months): Most significant weight reduction occurs during this period

• Plateau phase (12+ months): Weight stabilises; continued treatment helps maintain losses

Common side effects that may affect treatment adherence include:

• Nausea and vomiting (usually temporary, improving after several weeks)

• Diarrhoea or constipation

• Abdominal discomfort

• Fatigue

• Injection site reactions

Important safety considerations include:

• Risk of hypoglycaemia if used with insulin or sulfonylureas

• Do not stop or reduce insulin rapidly without medical advice (risk of diabetic ketoacidosis)

• Maintain adequate hydration to prevent acute kidney injury

• Potential for gallbladder problems (pain, stones)

• Rare risk of intestinal obstruction

• Possible worsening of diabetic retinopathy in people with diabetes during rapid improvement in blood glucose

• For tirzepatide: use additional non-oral contraception for 4 weeks after initiation and each dose escalation

Patients should contact their GP if they experience: persistent vomiting preventing fluid intake, severe abdominal pain, signs of gallbladder disease, or unusual thyroid symptoms. Regular monitoring is essential throughout treatment.

If you experience any side effects, talk to your healthcare professional. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk or via the Yellow Card app.

Who Can Access GLP-1 Treatment in the UK?

Access to GLP-1 medications for weight management in the UK involves understanding both licensing (what the medicines are approved for) and NHS commissioning (who can receive them on the NHS).

Licensing (Marketing Authorisation): The MHRA has approved:

• Semaglutide (Wegovy) for adults with BMI ≥30 kg/m² or BMI ≥27 kg/m² with at least one weight-related comorbidity

• Liraglutide (Saxenda) with similar BMI criteria

NHS Access (NICE Guidance): According to NICE guidance (TA664 for semaglutide), NHS-funded treatment is more restricted and typically available for adults with:

• BMI ≥35 kg/m² with at least one weight-related comorbidity (such as hypertension, type 2 diabetes, dyslipidaemia, obstructive sleep apnoea, or cardiovascular disease)

For individuals from Black, Asian, and minority ethnic backgrounds, lower BMI thresholds may apply, recognising that these populations face increased metabolic risk at lower BMI levels.

NICE recommends treatment only within specialist weight management services, typically for a maximum of 2 years, and only if non-surgical weight management interventions have been unsuccessful.

Current NHS availability is limited. Due to high demand, global supply constraints, and budgetary considerations, access through NHS prescription remains restricted. Many specialist weight management services have waiting lists or strict prioritisation criteria. The NHS England pathway typically requires:

• Referral to a specialist weight management service

• Demonstrated engagement with dietary and lifestyle interventions

• Assessment of suitability and precautions

• Regular monitoring and review

Private prescription is an alternative route, though costs are substantial—typically £150-300 monthly depending on the medication and dose. Patients considering private treatment should ensure proper medical assessment, monitoring, and follow-up care.

Important precautions: These medicines are contraindicated in pregnancy. They are not recommended during breast-feeding. Caution is needed in people with severe gastrointestinal disease (e.g., gastroparesis). Patients should discuss any thyroid symptoms with their healthcare provider (as a precaution based on animal studies). A full medical assessment is essential before starting treatment.

Frequently Asked Questions