Obesity / Weight Loss

Defining obesity

There are many ways in which a person’s health in relation to their weight can be classified, but the most widely used method is body mass index (BMI).

BMI is a measure of whether you’re a healthy weight for your height. You can use the BMI healthy weight calculator to work out your score.

For most adults, a BMI of:

• 18.5 to 24.9 means you’re a healthy weight
• 25 to 29.9 means you’re overweight
• 30 to 39.9 means you’re obese
• 40 or above means you’re severely obese

BMI isn’t used to definitively diagnose obesity because people who are very muscular sometimes have a high BMI without excess fat.

But for most people, BMI is a useful indication of whether they’re a healthy weight, overweight or obese.

A better measure of excess fat is waist circumference, which can be used as an additional measure in people who are overweight (with a BMI of 25 to 29.9) or moderately obese (with a BMI of 30 to 34.9).

Generally, men with a waist circumference of 94cm (37in) or more and women with a waist circumference of 80cm (about 31.5in) or more are more likely to develop obesity-related health problems.

Risks of obesity

It’s very important to take steps to tackle obesity because, as well as causing obvious physical changes, it can lead to a number of serious and potentially life-threatening conditions.

These include:

• type 2 diabetes
• coronary heart disease
• some types of cancer, such as breast cancer and bowel cancer
• stroke

Obesity can also affect your quality of life and lead to psychological problems, such as depression and low self-esteem.

Causes of obesity

Obesity is generally caused by consuming more calories, particularly those in fatty and sugary foods, than you burn off through physical activity. The excess energy is stored by the body as fat.

Obesity is an increasingly common problem because for many people modern living involves eating excessive amounts of cheap, high-calorie food and spending a lot of time sitting down, at desks, on sofas or in cars.

Read about why sitting too much is bad for your health.

There are also some underlying health conditions that can occasionally contribute to weight gain, such as an under-active thyroid gland (hypothyroidism), although these type of conditions don’t usually cause weight problems if they’re effectively controlled with medication.