Severe obesity, defined as a BMI of 40 kg/m² or above (or 35 kg/m² with significant comorbidities), affects approximately 3% of adults in England and requires comprehensive, individualised treatment. For those seeking alternatives to gastric bypass surgery, the NHS offers a range of evidence-based options including sleeve gastrectomy, medication-based therapies such as GLP-1 receptor agonists, and structured lifestyle programmes. NICE guidance emphasises a tiered approach, beginning with non-surgical interventions and progressing to pharmacological or surgical treatments when appropriate. Understanding the full spectrum of available treatments—from total diet replacement programmes to newer injectable medicines like semaglutide—enables patients and healthcare professionals to make informed decisions aligned with clinical evidence, individual circumstances, and NHS eligibility criteria.

Understanding Class 3 (Severe) Obesity and Treatment Options in the UK

Class 3 (severe) obesity, clinically defined as a body mass index (BMI) of 40 kg/m² or above, or a BMI of 35 kg/m² with significant obesity-related comorbidities, represents a serious chronic condition affecting approximately 3% of adults in England (Health Survey for England, 2021). The term 'severe obesity' reflects the substantial health risks associated with this condition, including type 2 diabetes, cardiovascular disease, obstructive sleep apnoea, and certain cancers. The National Institute for Health and Care Excellence (NICE) recognises obesity as a complex, multifactorial disease requiring comprehensive, individualised treatment approaches.

Treatment pathways for people living with severe obesity in the UK follow a tiered approach, beginning with lifestyle interventions and progressing to pharmacological and surgical options when appropriate. NICE guidance (CG189: Obesity: identification, assessment and management) emphasises that weight management should be viewed as a long-term commitment rather than a short-term intervention. The NHS provides access to various treatment modalities, though eligibility criteria apply to ensure resources are allocated to those most likely to benefit.

The decision-making process involves careful assessment of multiple factors, including BMI (with consideration of lower thresholds for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family origin), presence of comorbidities, previous weight loss attempts, psychological readiness, and individual patient circumstances. Multidisciplinary team involvement is essential, typically including specialist physicians, dietitians, psychologists, and surgeons where bariatric surgery is considered. Understanding the full spectrum of available treatments enables patients and healthcare professionals to make informed decisions aligned with clinical evidence and individual needs.

It is important to recognise that no single treatment suits everyone. Success depends on sustained behavioural change, appropriate medical support, and realistic expectations about outcomes and potential complications. For further information, see the NHS page on Obesity (www.nhs.uk/conditions/obesity).

Non-Surgical Treatments for Severe Obesity

Non-surgical interventions form the foundation of obesity management and remain appropriate for many people with severe obesity. Tier 1 and 2 services within the NHS provide structured lifestyle modification programmes combining dietary advice, physical activity guidance, and behavioural support. These programmes typically run for 12–24 weeks (duration varies locally) and aim to achieve a 5–10% reduction in body weight, which can significantly improve metabolic health even in severe obesity (NICE CG189).

Dietary interventions for severe obesity may include:

• Total diet replacement programmes using low-calorie (800–1,200 kcal/day) or very low-calorie (fewer than 800 kcal/day) formulated products

• Structured meal plans focusing on portion control and nutrient density

• Behavioural strategies addressing emotional eating, food environment modification, and self-monitoring

NICE recommends that very low-calorie diets should only be used under medical supervision as part of a multicomponent weight management strategy, typically for a limited period (e.g., up to 12 weeks continuously or intermittently), with appropriate refeeding and maintenance support. These diets may be particularly useful for patients requiring rapid weight loss before surgery or to improve acute comorbidities.

Physical activity recommendations are tailored to individual capability, starting with achievable goals such as 10–15 minutes of daily activity and gradually increasing intensity and duration. For people with severe obesity, low-impact activities like swimming, cycling, or walking may be more sustainable than high-intensity exercise. The UK Chief Medical Officers recommend that adults should aim for at least 150 minutes of moderate-intensity activity per week, adapted to individual capability. Psychological support addresses underlying factors contributing to obesity, including depression, anxiety, binge eating disorder, and trauma-related eating patterns.

Whilst non-surgical treatments alone may achieve modest weight loss in severe obesity (typically 5–15% of body weight), they remain valuable either as standalone interventions or as preparation for surgical options. Long-term success requires ongoing support, and many NHS areas offer maintenance programmes to prevent weight regain. Local service availability and referral criteria may vary; check with your GP or local integrated care board (ICB) for details.

Gastric Bypass Alternatives: Surgical Options

For patients meeting NHS criteria for bariatric surgery, several procedures offer alternatives to Roux-en-Y gastric bypass (RYGB), each with distinct mechanisms, benefits, and risk profiles. Sleeve gastrectomy has become the most commonly performed bariatric procedure in the UK, involving removal of approximately 75–80% of the stomach to create a tubular 'sleeve'. This restrictive procedure reduces stomach capacity and decreases production of the hunger hormone ghrelin, typically achieving 20–25% total body weight loss (or 60–70% excess weight loss) at two years (BOMSS/NHS data).

Sleeve gastrectomy offers several advantages over gastric bypass:

• Simpler surgical technique with shorter operative time

• No intestinal rerouting, reducing malabsorption risks

• Lower risk of internal hernias and bowel obstruction

• Preservation of pyloric valve, maintaining more normal gastric emptying

However, sleeve gastrectomy is irreversible and may cause or worsen gastro-oesophageal reflux disease (GORD) in some patients. For people with significant pre-existing GORD or oesophagitis, RYGB may be the preferred option. All patients require lifelong vitamin and mineral supplementation (typically multivitamin, calcium, vitamin D, and vitamin B12) and structured long-term follow-up to monitor nutritional status and detect complications early.

Adjustable gastric banding involves placing an inflatable silicone band around the upper stomach, creating a small pouch that limits food intake. Whilst this procedure is reversible and has the lowest perioperative risk, it typically achieves less weight loss (10–15% total body weight loss, or 40–50% excess weight loss) and has fallen out of favour due to higher revision rates and band-related complications.

Biliopancreatic diversion with duodenal switch represents a more complex malabsorptive procedure reserved for patients with BMI above 50 kg/m² or those requiring maximum metabolic effect. This operation combines sleeve gastrectomy with extensive intestinal bypass, achieving superior weight loss (30–40% total body weight loss) and diabetes remission but requiring lifelong intensive nutritional supplementation and monitoring. This procedure is rarely commissioned on the NHS and is confined to highly specialised centres.

NICE guidance (CG189) supports offering a choice of procedures based on individual clinical circumstances, patient preference, and local surgical expertise. All bariatric procedures require lifelong dietary modifications, vitamin supplementation, and regular follow-up to optimise outcomes and detect complications early. For further information, see the NHS page on Weight loss surgery (bariatric surgery) and the British Obesity & Metabolic Surgery Society (BOMSS) patient resources.

Medication-Based Treatments for Severe Obesity

Pharmacological interventions play an increasingly important role in managing severe obesity, either as standalone treatment or as an adjunct to lifestyle modification. Several medicines are licensed for weight management in the UK, though NHS prescribing is governed by strict NICE criteria and local integrated care board (ICB) formularies.

Orlistat (Xenical 120 mg; Alli 60 mg over-the-counter) remains the most widely available anti-obesity medicine in the UK. This lipase inhibitor reduces dietary fat absorption by approximately 30%, promoting modest weight loss of 2–3 kg beyond lifestyle intervention alone. Orlistat 120 mg is available on NHS prescription for adults with BMI ≥30 kg/m² (or ≥28 kg/m² with comorbidities such as type 2 diabetes or hypertension) who have demonstrated commitment to dietary change. The standard dose is 120 mg taken with each of the three main meals containing fat (maximum three capsules daily). Treatment should be discontinued after 12 weeks if the person has not lost at least 5% of their initial body weight since starting drug treatment (orlistat Summary of Product Characteristics, MHRA/EMC).

Common adverse effects include:

• Oily stools and faecal urgency (particularly with high-fat meals)

• Flatulence with discharge

• Reduced absorption of fat-soluble vitamins (A, D, E, K)

Patients should take a multivitamin supplement at bedtime (at least 2 hours after orlistat) when using this medicine. Orlistat may interact with ciclosporin, warfarin, and other medicines; check the British National Formulary (BNF) or Summary of Product Characteristics (SmPC) before prescribing.

GLP-1 receptor agonists represent a newer class of medicines originally developed for type 2 diabetes. Semaglutide (Wegovy) and liraglutide (Saxenda) work by mimicking the incretin hormone GLP-1, which regulates appetite, slows gastric emptying, and enhances insulin secretion. Clinical trials demonstrate 10–15% total body weight loss with semaglutide, significantly exceeding older medicines. These injectable medicines are administered weekly (semaglutide) or daily (liraglutide).

Semaglutide (Wegovy) is recommended by NICE (TA875: Semaglutide for managing overweight and obesity) for adults with at least one weight-related comorbidity and:

• BMI ≥35 kg/m², or

• BMI 30–34.9 kg/m² with prediabetes or cardiovascular disease

Semaglutide must be prescribed within a specialist weight management service and is funded for a maximum of 2 years. Treatment should be stopped if the person has not lost at least 5% of their baseline body weight after 6 months at the maintenance dose (NICE TA875; Wegovy SmPC).

Liraglutide (Saxenda) has more limited NHS commissioning; availability varies by local ICB formulary. Treatment should be discontinued after 12 weeks at the full 3.0 mg dose if the person has not lost at least 5% of their initial body weight (Saxenda SmPC).

Common side effects of GLP-1 receptor agonists include nausea, vomiting, diarrhoea, and constipation, usually improving with gradual dose escalation. These medicines should be used with caution in people with a history of pancreatitis or gallbladder disease. In people with type 2 diabetes, there have been reports of diabetic retinopathy complications; regular monitoring is advised (Wegovy/Saxenda SmPCs). Always check the BNF or SmPC for full contraindications, cautions, and interactions before prescribing.

Combination therapies such as naltrexone-bupropion (Mysimba) act on central appetite regulation pathways. This medicine is licensed in the UK but is not routinely funded by the NHS; commissioning varies by local ICB. Consult your local formulary for details.

All pharmacological treatments require concurrent lifestyle modification. Report suspected side effects via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk) or the Yellow Card app.

Choosing the Right Treatment: NHS Eligibility and Criteria

Accessing obesity treatment through the NHS follows structured pathways based on NICE guidance (CG189), with eligibility criteria ensuring appropriate resource allocation. Tier 3 specialist weight management services are typically available for adults with:

• BMI ≥40 kg/m², or BMI ≥35 kg/m² with significant comorbidities (lower thresholds apply for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family origin: consider intervention at BMI ≥27.5 kg/m² with comorbidities)

• Commitment to long-term lifestyle change

• Completion of Tier 2 community programmes (in most areas, though local pathways vary)

Tier 3 services provide intensive multidisciplinary support, including specialist dietetic input, psychological assessment, physical activity programmes, and consideration of pharmacotherapy. Many services require patients to demonstrate engagement and achieve specified weight loss targets before progressing to surgical assessment. Local referral criteria and service availability vary by integrated care board (ICB); check with your GP for details.

Bariatric surgery eligibility under NICE guidance (CG189) requires:

• BMI ≥40 kg/m², or BMI 35–40 kg/m² with obesity-related comorbidities that could improve with weight loss (such as type 2 diabetes or hypertension). Lower BMI thresholds apply for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family origin.

• Evidence of all appropriate non-surgical measures tried but failed to achieve or maintain adequate, clinically beneficial weight loss

• Fitness for anaesthesia and surgery

• Commitment to long-term follow-up, including lifelong nutritional supplementation and monitoring

For people with recent-onset (≤10 years' duration) type 2 diabetes, surgery may be considered as an alternative to lifestyle and pharmacological interventions at BMI ≥30 kg/m² (or ≥27.5 kg/m² for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family origin).

Factors influencing treatment selection include patient preference, surgical risk assessment, presence of gastro-oesophageal reflux disease (favouring bypass over sleeve), severity of metabolic disease, and local service configuration. Patients should receive comprehensive information about expected outcomes, potential complications, dietary changes, and the need for lifelong vitamin supplementation and monitoring.

It is essential to contact your GP if you experience:

• Persistent difficulty losing weight despite lifestyle efforts

• Obesity-related health complications

• Psychological distress related to weight

Your GP can refer you to appropriate NHS weight management services and discuss whether you meet criteria for specialist intervention. Private treatment options exist but require careful consideration of costs, ongoing support requirements, and complication management pathways. For further information, see NICE CG189 (Obesity: identification, assessment and management), NHS England/BOMSS commissioning guidance, and your local ICB referral criteria.

Frequently Asked Questions