Weight Management (Obesity & Metabolic Health)

What this guide covers

This page summarises UK guidance on healthy weight, obesity and metabolic health. It explains trusted measures (BMI, waist-to-height ratio), effective changes to eating and activity, when medicines or surgery are considered on the NHS, and where to find support. It is not personal medical advice; speak to your GP or a registered clinician for advice tailored to you.

Quick self-check (BMI & waist-to-height)

BMI categories (adults)

Per NICE NG246, adults are typically classified as: healthy weight 18.5–24.9; overweight 25.0–29.9; obesity class I 30.0–34.9; class II 35.0–39.9; class III ≥40. NICE NG246

Important: For people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds, health risks occur at lower BMI. NICE advises using lower thresholds: overweight from 23.0 and obesity from 27.5. NICE NG246

Waist-to-height ratio

Waist-to-height ratio (WHtR) complements BMI and predicts risk from central adiposity. Adults should try to keep their waist to less than half their height (WHtR < 0.5). NICE classifies: healthy 0.40–0.49, increased risk 0.50–0.59, high risk ≥0.60. NICE NG246

Use the NHS BMI tool if helpful: NHS BMI calculator.

Why weight matters

Excess body fat—especially around the waist—increases the risk of type 2 diabetes, high blood pressure, dyslipidaemia, cardiovascular disease, fatty liver disease, sleep apnoea and some cancers. Even a 5–10% weight reduction improves blood pressure, glucose and lipids. NICE NG246

What actually works (evidence)

• Structured behaviour programmes with food, activity and behaviour change components, tailored to the individual, are effective. NICE NG246
• Calorie deficit with adequate protein and fibre supports loss and maintenance; diverse dietary patterns can work if sustained. NICE NG246
• Physical activity aids health and helps maintain weight loss: aim for 150 minutes/week moderate activity (or 75 minutes vigorous) plus muscle-strengthening twice weekly. UK CMO guidelines, NHS
• Low-energy and very-low-energy diets (including total diet replacement) can be effective when clinically supervised and followed by structured food reintroduction and maintenance support. NICE NG246 (PDF)
• NHS programmes exist for eligible people (e.g., NHS Digital Weight Management; Type 2 Diabetes “Path to Remission” low-calorie programme). NHS England, NHS T2 Remission
• Medicines and metabolic/bariatric surgery are options for some people—see below for NHS criteria.

Diet approaches (including NHS programmes)

There is no single “best” diet. Choose a culturally appropriate, affordable pattern that creates a sustainable energy deficit and prioritises whole foods, lean protein, vegetables, fruit, legumes, wholegrains, and healthy fats.

Low-/very-low-energy diets

NICE supports low-energy diets and, in select cases, very-low-energy diets (often as total diet replacement) when supervised and followed by structured maintenance. NHS England’s Type 2 Diabetes “Path to Remission” programme uses ~800–900 kcal/day soups and shakes for 12 weeks before food reintroduction; about a third of completers achieved remission in pilots. NICE NG246 (PDF), NHS England, Diabetes UK

Free NHS support

• NHS Better Health: 12-week weight loss plan (app)
• NHS Digital Weight Management Programme (referral required)

Safety: Do not start very-low-calorie diets, total diet replacement, or significant changes if pregnant, under 18, frail, or with complex medical conditions unless advised by your clinician.

Physical activity that helps

• Build to 150 minutes/week of moderate aerobic activity (e.g., brisk walking, cycling) or 75 minutes vigorous, plus strength work twice weekly. Break up long sitting periods. NHS guidance, UK CMO 2019
• Activity supports heart, mood and sleep, and helps prevent weight regain after loss.

Behaviour change that sticks

• Plan your food (regular meals, protein & fibre at each meal, fewer ultra-processed foods).
• Environment: keep high-calorie snacks out of sight; have fruit/veg ready to eat.
• Sleep & stress: aim for regular sleep; use stress-reduction techniques; seek support if stress eating is a problem.
• Alcohol: cutting down reduces calorie intake and improves metabolic markers.
• Medications: some drugs affect weight—ask your GP/pharmacist before changing anything.

Medicines for weight management (NHS eligibility)

Medicines are used alongside diet, activity and behavioural support. Eligibility and availability are tightly controlled.

Semaglutide (Wegovy)

NICE recommends semaglutide for adults within a specialist service (usually tier 3/4) for up to 2 years, if there is ≥1 weight-related comorbidity and either BMI ≥35, or BMI 30–34.9 plus criteria for specialist referral. Use lower BMI thresholds (−2.5 kg/m²) for the ethnic groups listed above. Consider stopping if <5% weight loss at 6 months. NICE TA875

Tirzepatide (Mounjaro)

NICE recommends tirzepatide for adults with initial BMI ≥35 and ≥1 weight-related comorbidity, alongside reduced-calorie diet and physical activity. Lower BMI thresholds apply for certain ethnic groups. NHS England is phasing access over several years with prioritisation by BMI and number of comorbidities. NICE TA1026

Other options

Orlistat may be considered in some cases; other agents may be used for diabetes with weight benefit, guided by clinical need. All medicines require discussion of side-effects, contraindications, and stopping rules. NICE NG246

Metabolic/bariatric surgery (who is referred)

Referral for surgical assessment is offered if:

• BMI ≥40, or 35–39.9 with a significant health condition that could improve with weight loss (e.g., type 2 diabetes, OSA, hypertension, NAFLD). Lower BMI thresholds (−2.5 kg/m²) apply for certain ethnic groups. NICE NG246 (PDF)
• Expedited assessment is advised for recent-onset type 2 diabetes: BMI ≥35 (offer) or BMI 30–34.9 (consider). NICE NG246 (PDF)

If surgery is considered, there is a comprehensive MDT assessment and lifelong follow-up. NICE NG246 (PDF)

Children & young people

Use BMI centile (age/sex adjusted) and, where appropriate, waist-to-height ratio. Overweight is at/above the 91st centile; clinical obesity 98th; severe obesity 99.6th. Always seek advice from a GP, health visitor or school nurse; focus on family-wide healthy habits and safeguarding against stigma or disordered eating. NICE NG246

When to see your GP or practice team

• If BMI is in the obesity range or WHtR ≥0.5, or you have weight-related conditions (e.g., high BP, prediabetes/diabetes, OSA, fatty liver).
• If you’re considering an NHS programme, medicines, or surgery.
• If medicines or life events are affecting weight, or you have rapid weight change.
• If you’re pregnant, planning pregnancy, or breastfeeding—seek tailored advice.

FAQs

Can exercise alone make me lose weight?

Diet creates most of the calorie deficit; activity protects health and helps prevent regain. Combine both for best outcomes. NHS guidance

Is there one “best” diet?

No single diet suits everyone. Evidence supports multiple patterns if they reduce energy intake and are sustainable. NICE NG246

Are weight-loss injections available from my GP?

Some people may be eligible for semaglutide or tirzepatide under NICE rules and local NHS availability. Access is usually via specialist services, with strict criteria and review points. TA875, TA1026

What’s the simplest risk check I can do at home?

Measure waist and height in the same units and divide waist by height. Aim for <0.5. See the “How to” section below. Jump to steps

Can total diet replacement (soups & shakes) help?

Yes, for some—when clinically supervised and followed by reintroduction and maintenance. The NHS runs a Type 2 Diabetes “Path to Remission” low-calorie programme in England. NHS England

How to measure your waist-to-height ratio (WHtR)

1. Stand upright. Find the bottom of your ribs and the top of your hips. Place the tape midway (usually just above the belly button).
2. Wrap the tape snugly (not tight) around your bare waist; breathe out normally and record your waist.
3. Measure your height. Use the same units for both.
4. Divide waist by height. Example: 96.5 cm ÷ 170 cm = 0.57.
5. Aim for <0.5 in adults (lower is better within a healthy range). NICE NG246

References

• NICE. Overweight and obesity management (NG246) (2025). Guideline • PDF
• NICE. Semaglutide for managing overweight and obesity (TA875) (2023). Recommendations
• NICE. Tirzepatide for managing overweight and obesity (TA1026) (updated 2025). Recommendations
• UK Chief Medical Officers. Physical Activity Guidelines (2019). Report • NHS summary
• NHS England. Type 2 Diabetes Path to Remission Programme. Overview
• NHS England. Digital Weight Management Programme. Overview