Struggling to lose weight: medical causes, tests and treatment options

The NHS explains that you put on weight when the body turns extra calories from food and drink into fat, often because of too little physical activity or eating and drinking more than the body needs. It goes on to say you may also find it harder to stay a healthy weight if you have an eating disorder or other mental health condition such as depression, a health condition or disability that limits activity, a learning disability, a health condition that causes weight gain, take certain medicines, have genes that make you more likely to gain weight, are over 55, or are going through the menopause or perimenopause.

NICE Clinical Knowledge Summaries (CKS) agrees that obesity reflects an imbalance between energy in and out, shaped by many factors including lifestyle, genetics, medical conditions and medication, and recommends that clinicians consider the broader determinants and context and seek permission before discussing weight. If you have been doing everything you were advised and the scales will not move, a medical review is reasonable rather than blaming yourself.

The NHS names three conditions in its overweight and obesity guidance, and its pages on each describe what to look for:

The NHS says certain medicines, including some steroids, antidepressants and beta blockers, can make it harder to stay a healthy weight, and advises speaking to a GP if you have a condition or take a medicine that does so. Do not stop a prescribed medicine on your own; a GP or pharmacist can review whether an alternative suits you. The NHS also notes that its overweight guidance includes people who are menopausal or perimenopausal, so a menopause discussion may be part of the picture.

CKS says BMI is the practical measure of overweight and obesity but should be interpreted with caution, and recommends measuring waist-to-height ratio as well when BMI is below 35. A waist-to-height ratio of 0.4 to 0.49 is healthy, 0.5 to 0.59 shows increased health risks and 0.6 or more shows high central adiposity. The NHS says to keep waist size to less than half your height. CKS notes lower BMI thresholds apply for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds.

The NHS advises seeing a GP if your BMI is in the overweight or obese range and you want help to lose weight, your waist is more than half your height, you have pre-diabetes, diabetes, high blood pressure, joint pain, high cholesterol, sleep apnoea or heart disease, have a family history of obesity, or have or suspect an eating disorder such as binge eating. The sources used here do not list a fixed set of tests, so ask what is being checked and why.

The NHS suggests eating and drinking fewer calories than the body uses, doing more physical activity, aiming to lose 1 to 2 lb (0.5 to 1 kg) a week, cutting down on alcohol, being active for 45 to 60 minutes a day in shorter sessions if needed, and setting realistic goals while being kind to yourself. It says just losing 5 to 10 per cent of body weight can improve health. CKS says multicomponent interventions are the treatment of choice, tailored to preferences, fitness, health and lifestyle, with strategies to increase activity, improve eating behaviour and diet quality, and reduce energy intake.

The NHS says a GP can refer for weight management programmes, medicines or surgery, and can help you get support for other conditions affecting weight, including mental health conditions. Programmes may include one-to-one coaching, cognitive behavioural therapy, group support, online exercise classes and healthy eating advice. You can self-refer to some, and people needing more support may be referred to a specialist weight management service or offered support from a dietitian for a very low calorie diet, which the NHS says is not suitable or safe for everyone.

The NHS says that depending on BMI and other health conditions you may be able to have medicines to help you lose weight. Some reduce appetite and help you feel fuller for longer (GLP-1 and GIP agonists), and another stops the body absorbing as much fat from food. They are usually prescribed alongside diet and lifestyle advice, and support should be offered after stopping. CKS says drug treatment should be considered as an adjunct to lifestyle interventions for adults with a BMI of 30 or more, or 27 or more with risk factors such as type 2 diabetes, hypertension or dyslipidaemia. These are prescription-only medicines, so suitability, side effects and monitoring need a clinician's assessment.

The NHS says surgery may be offered if your BMI is 40 or over, or 35 or over with other health conditions that could improve with weight loss, with lower thresholds for some ethnic backgrounds. CKS describes bariatric surgery as the option of choice when other interventions have not worked for adults with a BMI above 50. After surgery the NHS says there are regular check-ups for 2 years.

NHS support runs through GPs, local weight management services and specialist services, with waiting times that vary by area. Private clinics may offer faster consultations and tests. Whichever you use, be cautious of anyone who promises rapid results, sells supplements as the main treatment, or recommends a prescription medicine without a proper assessment. Ask what tests are done, who monitors you, and what support continues after treatment stops.