Do I Need to Lose Weight?

This page describes the main ways we use to measure your weight: BMI and waist circumference. These can let you know if you are underweight, a healthy weight, or overweight and the impact this can have on your health.



Body Mass Index

 Body Mass Index (BMI) is a measurement that uses your height and weight to find out if your weight is putting your health at risk.

To work out your BMI:

  1. Measure your height (meters)
  2. Measure your weight (kilograms)
  3. BMI = Weight (kg) ÷ (Height (m) x Height (m))

For example:

  1. Height = 1.65 meters
  2. Weight = 87 kilograms
  3. BMI = 87 ÷ (1.65 x 1.65) = 31.9
  4. Your BMI = 31.9 kg/m2

You can also work with a BMI index chart.

Using this chart, find your weight and draw a line down from this. Your BMI is where the two lines meet.

Alternatively, try the BMI healthy weight calculator to find out your BMI.

As the table below outlines, the BMI can be split into four different categories.

BMI Categories




Implication to Health

European Adult

Asian Adult*


May need to gain weight

Less than 18.4

Less than 18.4

Healthy Weight

Aim to stay this weight

18.5 – 24.9

18.5 – 22.9


Increased risk to health

25 – 29.9

23 – 27.4


High risk to health

Greater than 30

Greater than 27.5

Limitations of BMI

 The BMI is a useful measure, but it is only a guide and does have some limitations:

  • It is only for use in adults over 18 years of age
  • It does not apply to pregnant women
  • It is not a good indicator of body fatness. A very muscular person (professional athlete) may have a high BMI when body fat is at a healthy level, because muscle weighs more than fat

How Do I Shape Up?

 People who carry weight around the middle (“apple shaped”) have greater health risks when compared to those who carry weight around their hips (“pear shaped”), even if both are overweight.  As well as checking your BMI it is also important to measure your waist size, as this can tell you if you are at increased risk.

To measure your waist:

  • Find the bottom of your ribs and top of your hips
  • Wrap a tape measure midway between these points
  • Breathe out naturally before taking the measurement

You may find this video useful when measuring your waist circumference.

Waist Circumference Classifications 


Increased Risk

Severe Risk

Men (European, White)

Greater than 94cm (37”)

Greater than 102cm (40”)

Men (African–Caribbean, South Asian)*


Greater than 90cm (35.5”)

Women (European, White)

Greater than 80cm (32”)

Greater than 88cm (35”)

Women (African–Caribbean, South Asian)*


Greater than 80cm (32”)

 There are different measurements in both BMI and waist for different ethnicities as research shows that if you are South Asian, African–Caribbean, Black African, Chinese, Middle Eastern or have two more different ethnic groups you are at an increased risk of certain health conditions at lower thresholds when compared to those from white European backgrounds. 

Additional Resources

 More information and support to help with weight management can be found below:

The NHS has developed a free, twelve-week guide which combines advice on healthy eating and physical activity:

The British Heart Foundation has produced a detailed information leaflet to support weight loss:

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