Overweight

Overweight is a body mass index (BMI) of 25 to 29.9 kg/m2 in adults (23 to 27.4 kg/m2 in Asian populations), a stage at which health risk starts to rise, especially when fat is central. It is common (about 30 to 40 percent of adults) and is a window for prevention of obesity, type 2 diabetes and cardiovascular disease.

• Waist circumference is a better marker of risk than BMI alone: increased above 94 cm in men and 80 cm in women (90 cm and 80 cm in South Asian men and women), substantially increased above 102 cm and 88 cm. A waist to height ratio of 0.5 or more indicates central adiposity at any BMI.
• BMI misclassifies muscular people and older adults with low muscle mass; it should be interpreted with waist and body composition.
• Causes: energy intake above expenditure, low activity, short sleep, stress, alcohol, medicines (antidepressants such as mirtazapine and amitriptyline, antipsychotics, corticosteroids, insulin, sulfonylureas, valproate, beta blockers), pregnancy, menopause, smoking cessation, hypothyroidism.
• Risks: progression to obesity (about 1 in 10 per year gain 5 kg or more), diabetes, hypertension, fatty liver, osteoarthritis, sleep apnoea, and some cancers.

• Often no symptoms. Weight gain over time, clothing size changes, joint aches, snoring, breathlessness on exertion.
• Examination: weight, height, BMI, waist, blood pressure, skin (acanthosis nigricans), signs of endocrine disease when weight gain is rapid.
• History: weight trajectory, diet, activity, alcohol, sleep, medicines, smoking status, mood, family history of diabetes and cardiovascular disease, previous gestational diabetes, polycystic ovary syndrome symptoms.
• Red flags: rapid unexplained weight gain, purple striae, proximal weakness, new hypertension, hirsutism and irregular cycles, swelling (oedema, ascites), cold intolerance.

• Measure height, weight, BMI, waist circumference, and blood pressure.
• Assess risk with HbA1c or fasting glucose, lipid profile, liver tests, and urine albumin to creatinine ratio when risk factors are present (waist above the threshold, age over 40, family history, hypertension, ethnic group at risk).
• Thyroid stimulating hormone when symptoms or rapid gain suggest hypothyroidism.
• Further tests (cortisol, testosterone, pelvic ultrasound) only when clinical features suggest an endocrine cause.
• Screen for sleep apnoea (snoring, witnessed apnoeas, sleepiness).
• Differentials: oedema, ascites, muscular build, pregnancy, hypothyroidism, Cushing syndrome.

Brief advice and goal setting

• Use a non-judgemental conversation, ask permission, discuss health benefits, and agree on a realistic goal: prevent further gain and lose 5 percent of body weight in 6 to 12 months.

Diet

• A moderate energy deficit of about 300 to 500 kcal per day (about 1500 to 1800 kcal for women and 1800 to 2200 kcal for men), plant rich, Mediterranean style eating; protein 1.0 to 1.2 g/kg per day; reduce sugar sweetened drinks, alcohol, refined snacks, large portions and ultra processed food; eat slowly, use smaller plates, and plan meals.
• Self-monitoring: food diary or app, weekly weight, and a fitness tracker.

Physical activity

• At least 150 to 300 minutes of moderate aerobic activity per week (brisk walking) or 75 to 150 minutes of vigorous activity, strength training twice per week, and daily steps of 7,000 to 10,000. Break up long periods of sitting every 30 minutes.

Sleep and behaviour

• Sleep 7 to 8 hours; stress management; behavioural support or commercial or community weight management programmes for 12 weeks or longer.

Medicines (selected patients)

• Considered at BMI 27 or more with a weight related condition (prediabetes, hypertension, dyslipidaemia, sleep apnoea) when lifestyle changes fail after 3 to 6 months: semaglutide 2.4 mg subcutaneously weekly (start 0.25 mg weekly, increase every 4 weeks through 0.5, 1, 1.7 to 2.4 mg), tirzepatide 2.5 mg weekly increasing by 2.5 mg every 4 weeks to 5 to 15 mg, liraglutide 3 mg daily (start 0.6 mg, increase weekly by 0.6 mg), or orlistat 120 mg three times daily with meals. Monitor for gastrointestinal effects, gallstones, pancreatitis; avoid in pregnancy and in those with medullary thyroid carcinoma or multiple endocrine neoplasia type 2.
• Metformin 500 mg increasing to 1 g twice daily in prediabetes with BMI above 30, or when antipsychotics cause weight gain.

Review medicines that promote weight gain, and switch when feasible (for example bupropion in place of mirtazapine in depression; metformin or topiramate where suitable).

Special groups

• Pregnancy: advised gestational weight gain is 7 to 11.5 kg for overweight; folic acid 400 micrograms daily (5 mg for BMI 30 or more); no dieting; aspirin 75 to 150 mg daily from 12 weeks if other pre-eclampsia risk factors.
• Menopause: strength training and protein intake maintain lean mass; weight gain is typically central.
• Children: family based approach, avoid weight loss diets, and target healthy habits; measure BMI centile.
• Older adults: aim at stable weight and preserving muscle with resistance exercise and adequate protein; caution with calorie restriction.
• South Asian, Black African and other high risk groups: act at lower BMI and waist thresholds.

Follow up

• Review at 4 to 6 weeks, then every 3 months for the first year; recheck weight, waist, blood pressure; repeat HbA1c and lipids annually or at 1 year if risk is raised.
• Refer to a weight management service if BMI progresses to 30 or more, complications appear, or the goals are not met.