BMI written on a chalk board with fruit and veg, scales and office items near it

What is BMI and why does it matter?

What’s your Body Mass Index and what do the numbers really mean?

You have probably heard of BMI as a method of measuring whether you are a healthy weight. BMI stands for body mass index. As the name suggests, it doesn’t just measure your weight but assesses your overall mass. Experts think this is a far better reflection of health as after all, everybody is built differently.

BMI uses your height and weight to place you in underweight, healthy, overweight, or obese ranges. Whilst it’s not an exact reflection of your health, it’s a useful starting point. Once you know your current BMI, you can make changes to lose or gain weight until you are healthier.

How does it calculate your BMI?

BMI calculators divide your weight by your height. For most adults (excluding athletes or anyone with significant muscle mass), target BMI is 18.5-24.9. There is a different calculation for children aged 2-18 which takes age and gender into account.

What does your BMI mean?

Once you have calculated your BMI, compare it against the guidelines.

Below 18.5 – underweight range

18.5 to 24.9 – healthy weight range

25 to 29.9 – overweight range

30 to 39.9 – obese range

 Is BMI the only measurement you should use?

You’ll notice that your Doctor won’t only rely on BMI to assess your health. Various factors could skew your BMI, putting you in one of the unhealthy ranges even if you are actually in good health. These factors include muscle mass (muscle is denser than body fat), and ethnicity.

Remember that BMI doesn’t measure your body composition. That is, it can’t tell how much of you is body fat, muscle, bone, water (or anything else)- but it is a good place to start. If you are worried about your weight, talk to your doctor about lifestyle changes you can make to reach a healthier, happier body weight.

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