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Overweight and Obesity

NICE guideline [NG246] Overweight and Obesity Management. Published: Jan 2025.

Identification and Assessment Guidelines

NICE recommends BMI as a practical measure of overweight and obesity.
  • BMI: weight (kg) / (height in m)2

NICE also recommends measuring waist-to-height ratio in those with BMI <35 kg/m2
  • Waist-to-height ratio is a practical estimate of central adiposity, which can be used to assess and predict health risks

Classification BMI range (kg/m2)
Healthy weight 18.5 - 24.9
Overweight 25.0 - 29.9
Obesity class 1 30.0 - 34.9
Obesity class 2 35.0 - 39.9
Obesity class 3 ≥40.0

NICE recommends lower BMI thresholds in people with South Asian, Chinese, other Asian, Middle Eastern, Black African, and  African-Caribbean backgrounds as they are prone to central adiposity and their cardiometabolic risk occurs at lower BMI:
  • Overweight: BMI 23 - 27.4 kg/m2
  • Obesity: BMI ≥27.5 kg/m2
  • Obesity class 2 and 3: minus 2.5 kg/m2 from the above thresholds

 

Note that BMI is NOT a direct measure of central adiposity.

BMI should be interpreted with caution in:

  • Adults with high muscle mass
  • ≥65 y/o

The following waist-to-height classification can be used for people with BMI <35 kg/m2 of both sexes and all ethnicities, including adults with high muscle mass.
 
Classification Waist-to-height ratio range
Healthy 0.4 - 0.49
Increased 0.5 - 0.59
High ≥0.6

Centiles and standard deviations should be used to classify BMI.
 
Overweight BMI 91st centile + 1.34 SD
Clinical obesity BMI 98th centile + 2.05 SD
Severe obesity BMI 99.6th centile + 2.68 SD

The classification is the same as adults:
 
Overweight BMI 91st centile + 1.34 SD
Clinical obesity BMI 98th centile + 2.05 SD
Severe obesity BMI 99.6th centile + 2.68 SD
 

Management Guidelines

Key point is employing a multicomponent management strategy with long-term support, including:
  • Increase physical activity changes, and
  • Reduced-calorie diet

All medicines for weight management should be used alongside a reduced-calorie diet and increased physical activity.
 
Drug Class Indications Important side effects Pregnancy and contraception
Orlistat Lipase inhibitor
  • BMI ≥30 kg/m2, or
  • BMI ≥28 kg/m2 + associated risk factors
  • Flatulence
  • Oily fatty stools
  • Fat-soluble vitamin deficiency
  • Gallstones and kidney stones
  • Rare but risk of serious hepatitis
 Do not use
Tirzepatide GLP-1 and GIP agonist
  • BMI ≥35 kg/m2, and
  • At least 1 weight-related comorbidity
  • GI upset is common but not serious (e.g. nausea, vomiting, diarrhoea, constipation, bloating)
  • Pancreatitis
  • Bowel obstruction
  • Thyroid C-cell tumour (thus contraindicated in personal / family history of medullary thyroid carcinoma or MEN2)
Semaglutide GLP-1 agonist
  • BMI ≥35 kg/m2, and
  • At least 1 weight-related comorbidity
Liraglutide
  • BMI ≥35 kg/m2, and
  • Non-diabetic hyperglycaemia
 

For tirzepatide, semaglutide and liraglutide, NICE recommends using lower BMI thresholds (usually reduced by 2.5 kg/m2) for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean ethnic backgrounds.
 

Medications are NOT generally recommended for those <12 y/o

  • Only consider in exceptional circumstances, if severe comorbidities are present

Refer to specialist overweight and obesity management service to assess for bariatric surgery eligibility if:
  • BMI ≥40 kg/m2 or BMI 35-39.9 kg/m2 + significant health conditions that can be improved if they lose weight, and
  • Patient agrees to necessary long-term follow-up after surgery

Early assessment for bariatric surgery should be considered in:
  • BMI 30-34.9 kg/m2, and
  • Recent-onset type 2 diabetes (diagnosed <10 years), and
  • Receiving, or will receive, assessment in a specialist overweight and obesity management service

Consider referral for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African–Caribbean background using a lower BMI threshold (reduced by 2.5 kg/m2)

NICE did not make any specific recommendations on which surgical interventions to use, but it is important to know about the commonly used bariatric surgeries.
 
Procedure Type Mechanism Disadvantages
Sleeve gastrectomy Restrictive Removes ~80% of the stomach (greater curvature)
  • Irreversible
  • May worsen GORD
Adjustable gastric banding Inflatable band around the upper stomach, adjustable via subcutaneous port
  • Less weight loss than other methods
  • Risk of band slippage
Roux-en-Y gastric bypass Restrictive + malabsorptive A small stomach pouch is created and connected to the intestine to bypass the duodenum and proximal jejunum
  • Nutrient deficiency (those absorbed in the duodenum and proximal jejunum) (e.g. iron, folate)
  • Vitamin B12 deficiency (intrinsic factor secreted by the stomach)
  • Dumping syndrome
Biliopancreatic diversion with duodenal switch Sleeve gastrectomy + bypass of most of the small intestine
  • Nutrient deficiency
  • Vitamin B12 deficiency (intrinsic factor secreted by the stomach)
  • Protein-calorie malnutrition

References

Author: Adams Lau
Reviewer:
Last edited: 15/08/25