Overweight and obesity as a health risk: what it means and what helps

The NHS describes overweight and obesity as having more body fat than your body needs. Doctors use body mass index (BMI), which relates weight to height, as a first screening measure. For most adults, a BMI of 25 to 29.9 falls in the overweight range and 30 or more in the obese range.

BMI is a rough guide. The NHS points out that it cannot distinguish muscle from fat, so someone with a lot of muscle may be placed in the overweight or obese category without having much body fat. It also recommends a waist to height ratio for people with a BMI under 35, as a way of checking whether too much fat is carried around the tummy, with a target of a waist less than half your height.

Because the risk of ill health starts at lower BMI values for some groups, the NHS gives different thresholds for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds: a BMI of 23 to 27.4 is overweight and 27.5 or higher is obese.

According to the NHS, living with overweight and obesity increases the risk of many serious conditions. It also says that living with obesity is likely to lower life expectancy by between 2 and 10 years, and can cause everyday problems that affect quality of life.

• Type 2 diabetes, heart disease, stroke and high blood pressure.

• Some cancers, such as breast cancer, womb cancer and bowel cancer.

• Osteoarthritis and fatty liver disease.

• Day-to-day problems such as breathlessness, difficulty moving around, tiredness, joint and back pain, snoring and low mood.

The NHS lists being obese or overweight among the risk factors for atherosclerosis, the fatty narrowing of the arteries that underlies coronary heart disease. Weight tends to work alongside other factors: it can contribute to high blood pressure, high cholesterol and diabetes, and the NHS says diabetes can more than double the risk of coronary heart disease.

The NHS also lists being overweight and not very physically active as a reason to be more at risk of type 2 diabetes, and says it may be possible to prevent type 2 diabetes, or put it into remission, by losing weight and improving diet. This is one reason a GP may check blood pressure, cholesterol and blood sugar when weight is a concern.

The NHS explains that weight is put on when the body turns extra calories from food and drink into fat, often because of not being active enough and eating and drinking more than the body needs, especially food and drink high in fat and sugar.

It is not only a matter of effort. The NHS says you may find it harder to stay a healthy weight if you have an eating disorder or another mental health condition such as depression, a health condition or disability that makes it hard to be active, or a learning disability. Conditions that cause weight gain include an underactive thyroid and Cushing's syndrome, and the NHS also names polyendocrine metabolic ovarian syndrome (PMOS), previously called PCOS. Some medicines, including some steroids, antidepressants and beta blockers, can contribute, as can genes that make weight gain more likely, being over 55, and the menopause or perimenopause.

The NHS suggests seeing a GP if your BMI is in the overweight or obese range and you want help losing weight, your waist is more than half your height, you have pre-diabetes, diabetes, high blood pressure, joint pain, high cholesterol, sleep apnoea or cardiovascular disease, or you have a family history of obesity. It also advises seeing a GP if you have, or think you may have, an eating disorder such as binge eating.

It is worth mentioning any medicines you take and any symptoms such as persistent tiredness, feeling cold or a low mood, since a condition such as an underactive thyroid can be tested for with a blood test.

The first step the NHS describes is lifestyle change: eating and drinking fewer calories than your body uses and doing more physical activity. It suggests aiming to lose 1 to 2lbs, or 0.5 to 1kg, a week, being active for 45 to 60 minutes a day (in shorter sessions if you wish), cutting down on alcohol, and being kind to yourself because changing habits takes time.

If that is not enough, a GP can refer you for weight management programmes, medicines or surgery. Programmes may include one-to-one coaching, cognitive behavioural therapy, group support and online exercise classes, and the NHS says you can self-refer to some of them. Those who need more support may be referred to a specialist weight management service or a dietitian, and some may follow a very low calorie diet, which the NHS says is not safe or suitable for everyone.

Weight can be difficult to live with physically and emotionally. The NHS recommends support from NHS Better Health, talking to a GP about mental health or talking therapies, and joining a local or online support group. After weight loss medicines the NHS says you should be offered help to stay at a healthy weight, and after surgery you will have regular check-ups for 2 years.

Most weight management care is available through the NHS and local services, with referral by a GP. Some people choose private clinics, dietitians or commercial programmes, which can offer quicker access or more frequent contact. It is sensible to check that any provider is regulated, that medicines are prescribed after a proper assessment, and that there is a plan for support afterwards.