The diagnosis of obesity is defined by a body mass index over 30 kilograms per metre squared.

Explain underlying causes

Any clinical suspicion of underlying or associated diagnoses needs specific investigation and treatment before the obesity can be appropriately managed. For example further investigations and treatment for suspected Cushing’s or polycystic ovarian syndrome (PCOS), or treatment for hypothyroidism, diabetes or depression should all take priority.

Conversely, if no underlying medical condition is detected, this should also be discussed, as a proportion of patients may feel that there is an underlying imbalance or disease causing their obesity. It can be difficult to institute lifestyle change in such cases unless they fully understand their condition.

Address cardiovascular risk profile

Establish and explain the patient’s individual cardiovascular risk profile and institute appropriate plan.

Blood pressure

Ensure blood pressure is below 150/90 and, if not, start treatment. 

This is important for cardiovascular risk reduction and is also mandatory before considering sibutramine therapy, although the licence for this medication has recentlly been suspended.

Obstructive sleep apnoea

Obstructive sleep apnoea (OSA) may lead to poor quality of life, extreme fatigue and reduced capacity for exercise all of which make weight loss difficult. Untreated OSA also increases anaesthetic risk and so should be addressed before considering bariatric surgery.

Consider referral for formal sleep assessment if indicated.

Dietetic input

Specialist dietetic input is required in all cases. This may be most appropriately arranged through an eating disorder clinic, a diabetes specialist dietician, or a dietician with an interest in obesity depending on clinical need. 

Where orlistat is being considered, patients need to be reliably taking a <3% fat diet to prevent unpleasant side effects.

Lifestyle advice

Encourage regular aerobic exercise with supervised exercise programmes tailored for the obese where available: 'exercise on prescription'.

Where orthopaedic problems are present, consider referral for specialist assessment, although swimming can be safely recommended in almost all cases.

Drug treatment

National guidelines suggest that pharmacotherapy should be considered only after three months dietary and life style changes. Where portion size appears to be a major problem, sibutramine has been widely used with close blood pressure monitoring. However, recent cardiovascular safety concerns have led to the suspension of its licence.

Where diet appears to be particularly high in fat, orlistat may be more appropriate but must not be recommended without appropriate dietary changes. When used with a poor diet, unacceptable side effects of abdominal bloating, diarrhoea, steatorrhoea and faecal incontinence may occur.

Consider psychological or psychiatric assessment

Patients with apparent severe underlying psychological issues should be referred appropriately for help with these. This is also mandatory in such patients to help assess suitability for bariatric surgery. 

Suspected depression should be specifically addressed usually through the GP. 

Suspected eating disorders should also be addressed through a specialist eating disorder psychiatric unit.

Consider bariatric surgery

Bariatric surgery should be considered in patients with a BMI above 40 kg/m2, or over 35 kg/m2 with comorbidities according to NICE guidelines. However, this is clearly not appropriate for all patients.

It is usual to try lifestyle and medical means in the first instance. It is also mandatory to optimise the control of diabetes and other cardiovascular risks including sleep apnoea before referring for bariatric surgery. All patients need to have received specialist dietetic input before considering whether bariatric surgery is necessary or appropriate. Furthermore, patients need to understand how their lives are likely to be affected by surgery, as well as the risks and benefits involved.

Not all patients require formal psychological assessment prior to bariatric surgery, though this should always be considered and is often helpful.

Bariatric surgery should then only be performed in a specialist centre with appropriate specialist nursing and dietetic support for both the pre and post operative periods.

Follow up

Long term follow up is very helpful in managing obesity. However, this is most appropriately offered in a specialist weight management clinic, with a specialist dietician rather than an endocrinologist, as further medical tests are rarely required.

Following bariatric surgery, dietary supplements are frequently required, and monitoring for electrolyte, vitamin and mineral deficiencies may be indicated depending on the procedure undertaken.