How to Read the BMI Graph

B.M.I - what it's about

Body Mass Index, or BMI, is a measurement taken to determine your weight and health status. It is a measurement that relates to your height and weight that is then calculated to place you in a group that relates to the category relevant to you.

BMI can be used as tool by doctors to determine if a person is at an unhealthy weight and at risk for further complications.

The BMI categories;



BMI range – kg/m2 

Very severely underweight

less than 15.0

Severely underweight

from 15.0 to 16.0


from 16.0 to 18.5

Normal (healthy weight)

from 18.5 to 25


from 25 to 30

Obese Class I (Moderately obese)

from 30 to 35

Obese Class II (Severely obese)

from 35 to 40

Obese Class III (Very severely obese)

over 40

The aim is to fall into the 'healthy weight' category but bare in mind  the caveats below.

The Grey Area

As with many things, there are caveats here too! Generally BMI gives a good indication of weight and health. The higher your BMI, the heavier you are and the more likely you are to have health problems associated with being overweight.

However, BMI can sometimes be misleading. If we think about a fit but typical male rugby physique. Muscular definition will cause a healthy person to weigh more. This results in an elevated BMI, even though they are not overweight! It's a good idea to use other methods alongside BMI to verify your health status. That's one of the reasons we include waist to hip ratio so you ahve some context to your results. 

If you're not in the 'Healthy Weight' category

Assuming you're not an Olympian or of very muscular physique, you'll either be in a situation where (ideally) you will want to lose or gain weight.

The risks of being overweight or obese;

  • High blood pressure (hypertension)
  • High LDL cholesterol ("bad" cholesterol)
  • Low HDL cholesterol ("good" cholesterol)
  • High triglycerides
  • High blood glucose (sugar)
  • Family history of premature heart disease
  • Physical inactivity
  • Cigarette smoking

The risks of being underweight;

  • Poor bone health and oesteoporosis
  • Anaemia
  • Weakened immune system
  • Fertility and pregnancy complications

Any concerns you have should be directed to your GP - these lists are not exhaustive. Lets keep it simple - the aim is for you to be at a healthy weight for YOU, whatever your physique. Know that if you are overweight a reduction of just 5-10% of body weight will make you feel fab AND reduce your risks.

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