Weight Loss / Obesity Management in the UK: A Complete Teaching Guide for Doctors

1. DEFINITIONS AND BMI CLASSIFICATION

2. APPROACH AND LANGUAGE (NG246 - Mandatory Principles)

• Always ask permission before discussing a patient's weight. Respect their choice to delay or decline the conversation.
• Use person-first, non-stigmatising language: "living with obesity" not "obese patient."
• Identify the patient's own preferred terms for their weight.
• Avoid diagnostic overshadowing: if a patient presents with knee pain, address the knee pain first - do not immediately pivot to weight.
• Consider the wider determinants: childhood trauma, mental health, socioeconomic factors, ethnicity, medications that cause weight gain, recent pregnancy, and financial stress.
• Clinicians should reflect on their own biases about weight before engaging.
• A strong emphasis is placed on ongoing support given that obesity is a chronic condition, not an acute failure of willpower.

3. GP APPROACH: INVESTIGATION

History

• Duration and pattern of weight gain
• Dietary history (calorie intake, meal patterns, ultra-processed food)
• Physical activity levels
• Medications that promote weight gain: antipsychotics (olanzapine, clozapine), steroids, insulin, sulfonylureas, beta-blockers, tricyclic antidepressants, sodium valproate, lithium, thiazolidinediones
• Psychological history: depression, binge eating disorder, emotional eating
• Sleep history: obstructive sleep apnoea (ask about snoring, daytime somnolence, witnessed apnoeas)
• Family history of obesity, T2DM, CVD
• Social history: stress, housing, financial strain, night shifts, food environment
• Previous weight loss attempts

Examination

• Height, weight, BMI
• Waist circumference (if BMI < 35)
• Blood pressure
• Signs of secondary causes (see below)
• Signs of comorbidities: acanthosis nigricans (insulin resistance), xanthelasma (dyslipidaemia), lipodystrophy

Investigations: Ruling Out Secondary Causes

Routine Bloods for All Patients with Obesity (Comorbidity Screen)

• Fasting glucose and HbA1c (screen for T2DM and pre-diabetes)
• Fasting lipid profile (screen for dyslipidaemia)
• Liver function tests (metabolic dysfunction-associated steatotic liver disease / MASLD, previously NAFLD)
• Renal function and electrolytes
• TFTs (TSH at minimum)
• FBC (anaemia, polycythaemia)
• Uric acid if gout suspected
• Blood pressure (formally with correct cuff size - use large cuff)
• Consider HbA1c to assess for non-diabetic hyperglycaemia (prediabetes: HbA1c 42-47 mmol/mol or fasting glucose 5.5-6.9 mmol/L)
• ECG if considering pharmacotherapy or high CVD risk
• Consider liver USS if LFTs abnormal (screen for MASLD/steatohepatitis)
• Consider sleep study if OSA suspected

4. GP MANAGEMENT: THE TIERED APPROACH

Step 1 - Lifestyle Intervention (All Patients)

• NICE recommends a deficit of approximately 600 kcal/day from estimated total energy requirement
• Do not prescribe unduly restrictive or nutritionally unbalanced diets - they are not effective long-term and can be harmful
• Consider total diet replacement (low calorie diet 800-1600 kcal/day) short-term, but this is less nutritionally complete - only use with support
• Tailor to individual preferences, culture, and financial situation
• The NHS Eatwell Guide is the reference point

• Follow UK Chief Medical Officers' guidelines: 150 minutes moderate intensity or 75 minutes vigorous activity per week for adults
• Those with obesity may need 60-90 minutes/day of moderate activity to avoid weight regain
• Reduce sedentary time - any movement helps
• Supervised exercise programmes are effective alongside lifestyle coaching

• Multicomponent interventions combining dietary advice, physical activity support, and behaviour change strategies are the most effective
• Cognitive behavioural therapy (CBT) techniques
• Digital/app-based interventions can supplement face-to-face support (NICE behaviour change: digital and mobile health interventions guideline applies)
• Set realistic, personalised goals - a 5% body weight reduction at 6 months is the minimum clinically meaningful target, with greater benefits at 10-15%+

• NHS Weight Management Services (Tier 2 community services)
• Dietitian
• Exercise professional
• Weight management groups (e.g. NHS-commissioned commercial providers)

Step 2 - Pharmacotherapy

Step 3 - Referral to Specialist Weight Management Services (SWMS)

• BMI ≥ 50 (extreme obesity)
• Complex medical, psychological, or social needs
• Housebound or severe functional restriction from obesity
• Severe and enduring mental illness, learning disability
• Meets tirzepatide criteria in primary care but has additional complex needs requiring specialist input
• Consideration for bariatric surgery
• Rare genetic obesity syndromes

Step 4 - Bariatric Surgery

• BMI ≥ 40 kg/m², OR
• BMI 35-40 + significant comorbidity (T2DM, HTN, OSA, joint disease)
• All non-surgical options must have been tried and failed
• Patient must be fit for anaesthesia and committed to long-term follow-up
• Should be delivered by a multidisciplinary team including surgeon, dietitian, psychologist, and physician
• Lower BMI thresholds apply for South/East Asian populations

5. WARD / INPATIENT MANAGEMENT (Hospital Doctors)

On Admission

• Record height, weight, and BMI on every admission
• Use appropriately sized equipment: large blood pressure cuff, wide-bore cannulae, bariatric beds/chairs where needed
• Document whether the patient has had recent weight loss (intentional or unintentional - unintentional weight loss is a red flag for malignancy, malabsorption, or other systemic disease)

• Identify weight-promoting medications and consider alternatives where possible
• Review insulin regimens, antipsychotics, steroids
• Check whether GLP-1 agonist or tirzepatide needs to be paused (e.g. for elective surgery - usually hold 1 week prior due to delayed gastric emptying)

• Obesity is a major VTE risk factor
• LMWH dosing must be weight-adjusted - standard prophylactic doses are insufficient in high BMI patients
• Consult local protocol for bariatric dosing (e.g. enoxaparin 40 mg BD for BMI > 40 in many trusts)
• Apply TED stockings only if appropriate (risk of injury if poorly fitting)
• Encourage early mobilisation

Medical Comorbidity Management on the Ward

Anaesthetic / Peri-operative Considerations

• Inform anaesthetics early for any patient with BMI > 40 or OSA undergoing surgery
• Airway management is more difficult - experienced intubator required, have video laryngoscope available
• Positioning on theatre table requires bariatric tables and padding
• Post-operatively: semi-upright position, early mobilisation, adequate analgesia to facilitate breathing
• Gastric emptying is delayed (especially with GLP-1 agonists) - nil by mouth instructions may need extending; RSI is recommended

Nutrition on the Ward

• Obesity does not mean the patient is well-nourished - many patients with obesity are micronutrient deficient
• Involve dietitian early, especially post-bariatric surgery or if prolonged fasting
• Post-bariatric surgery patients: check for deficiencies of B12, folate, iron, vitamin D, thiamine (especially if vomiting - give thiamine to prevent Wernicke's)
• Do not place patients with obesity on standard hospital 1800 kcal meals without dietitian input
• MUST (Malnutrition Universal Screening Tool) should still be completed

Psychological Support on the Ward

• Acknowledge that hospital admission can be emotionally distressing for patients living with obesity due to stigma and practical barriers
• Ensure psychological or liaison psychiatry review if eating disorder, binge eating, or severe depression is present
• Do not use stigmatising language on ward rounds or in documentation

Discharge Planning

• Use the admission as an opportunity to signpost to weight management services (with patient's permission)
• Refer to GP for follow-up of newly identified comorbidities (e.g. T2DM, OSA diagnosed during admission)
• Ensure medications that contributed to weight gain are reviewed in the discharge summary
• If the patient meets criteria for GLP-1 agonist or tirzepatide, flag this for the GP in the discharge letter

6. WHEN TO SUSPECT AND INVESTIGATE SECONDARY CAUSES IN THE WARD SETTING

• Rapid onset weight gain without obvious cause
• Associated features: fatigue, cold intolerance, hair loss → TFTs
• Central obesity, striae, hypertension, new-onset diabetes, proximal weakness → overnight dexamethasone suppression test, 24-hr urine cortisol
• Young patient with severe obesity since childhood, hyperphagia, developmental delay → genetic workup, refer endocrinology
• Hypogonadism features → testosterone/LH/FSH
• Pituitary symptoms (headache, visual field defects, galactorrhoea) → pituitary MRI, prolactin, full pituitary screen

7. KEY NUMBERS TO REMEMBER FOR TEACHING

8. SUMMARY TABLE: GP vs. HOSPITAL DOCTOR ROLES

Recent Evidence Highlights

• Tirzepatide (SURMOUNT trials) produces approximately 20-22% weight loss at 72 weeks - greater than any previously approved agent. [NICE TA1026, December 2024]
• Semaglutide (STEP trials, PMID: 38752254 context): ~15% weight loss, benefits in heart failure and OSA demonstrated in recent systematic reviews
• Aerobic exercise meta-analysis (JAMA Network Open, 2024, PMID 39724371): dose-response relationship confirmed - more exercise = more weight loss, but even modest amounts are beneficial
• Weight loss in PCOS (Ann Intern Med, 2024, PMID 39496172): weight loss interventions significantly improve menstrual regularity, androgen levels, and metabolic markers in PCOS

Key Resources to Bookmark

• NICE NG246 - Overweight and obesity management (2025) - the master guideline
• NICE TA1026 - Tirzepatide (2024)
• NHS England interim commissioning guidance - tirzepatide rollout
• Society for Endocrinology - Specialist referral criteria (June 2025)