Obesity
Excess body fat that increases risk of diabetes, cardiovascular disease and cancer.
Overview
Obesity is defined by BMI ≥30 (or lower with high-risk ethnicity). It is a chronic, relapsing condition with strong biological drivers. Treatment combines dietary, behavioural and physical activity change; pharmacotherapy and bariatric surgery are options for selected patients.
Symptoms
- • Often asymptomatic
- • Breathlessness on exertion
- • Joint pain
- • Snoring or sleep apnoea
- • Reflux
Risk factors
- • Genetic predisposition
- • Sedentary lifestyle
- • Energy-dense diet
- • Certain medications (steroids, antipsychotics)
- • Hypothyroidism
Causes
- • Sustained positive energy balance
- • Hormonal and genetic factors
- • Environmental and socioeconomic factors
🚨 Red flags — seek urgent care
- • Symptoms of obstructive sleep apnoea with daytime sleepiness
- • Cardiovascular symptoms
- • Severe mobility loss
When to seek care
- • BMI ≥30 or weight gain affecting health
- • Co-existing diabetes, hypertension or sleep apnoea
- • Considering pharmacotherapy or surgery
Diagnosis
- • BMI ≥30 (or ≥27.5 in South Asian, Chinese, other high-risk ethnic groups)
- • Waist circumference for central adiposity (men ≥94 cm, women ≥80 cm — higher in some ethnicities)
- • Comorbidity screening: BP, lipids, HbA1c, LFTs, sleep apnoea, mood
Treatment
- • Multicomponent lifestyle programmes: dietary change (calorie deficit), 150–300 min/week activity, behaviour change
- • Pharmacotherapy: GLP-1 RAs (semaglutide, liraglutide), tirzepatide, orlistat — alongside lifestyle
- • Bariatric surgery (BMI ≥40, or ≥35 with comorbidity) — sleeve gastrectomy or Roux-en-Y bypass
- • Treat comorbid hypertension, dyslipidaemia, diabetes, obstructive sleep apnoea
- • Psychological support; address eating disorders and weight stigma
Prevention
- • Balanced diet rich in vegetables, fibre and whole grains; limit ultra-processed foods and sugary drinks
- • Daily physical activity; limit sedentary time
- • Adequate sleep (≥7 hours)
- • Address childhood obesity early
Complications
- • Type 2 diabetes, hypertension, dyslipidaemia
- • Cardiovascular disease and stroke
- • Multiple cancers (colorectal, breast, endometrial, oesophageal, pancreatic, kidney)
- • Obstructive sleep apnoea, NAFLD, gallstones
- • Osteoarthritis, depression, reduced fertility
Education & self-care
This guidance is reviewed by Dr. Handel Emery, MD, FRCP (UK) and last updated 2026-06-08. It is educational and not a substitute for professional medical advice.
Frequently asked questions
Are weight-loss injections safe?
GLP-1 medicines such as semaglutide are effective and broadly safe under medical supervision. They are not a substitute for sustained lifestyle change.
Are GLP-1 drugs like semaglutide a long-term solution?
They can produce 10–15% weight loss when combined with lifestyle change, but most weight returns if stopped. They are increasingly viewed as long-term treatment rather than short courses.
When is bariatric surgery considered?
Usually for BMI ≥35 with significant complications, or BMI ≥40 alone, after structured weight-loss attempts. It produces durable weight loss and improves or resolves type 2 diabetes in most patients.
Is BMI a fair measure?
BMI is a useful screen but does not capture muscle mass, fat distribution or ethnicity. Waist circumference, body composition and metabolic markers add a more complete picture.