Deirdre O Meara 
Knowing your body mass index, or BMI is an integral part of staying healthy and identifying your health risks. As such, it can aid in helping you make healthier choices moving forward. Below, are answers to the most commonly asked questions about BMI.
What is BMI?
As briefly mentioned above, BMI stands for your body mass index. It is the measure of body fat based on both your height and weight. While a regular scale is used to measure how much you weigh in pounds, the calculations of your BMI are much more complicated.
A body mass index is split into four different categories:
- Underweight
- Healthy weight
- Overweight
- Obese
Since they take your height into variation, what the scale shows for one person may have far worse (or far better) outcomes when measuring BMI. For example, let’s say that someone weighs 210 pounds – or 15 stones and measures 5’2’’. Taking their height and weight into consideration, their BMI is on the high side at 38.4. According to the BMI calculator, this is considered obese.
However, let’s take the same weight, but make the person 5’11. Despite having the same weight, the BMI calculator ranks them as overweight, instead of obese. Their lifestyles may be exactly the same, yet their body mass index totals differ due to their height.
If you’re looking to get in better health or stay on top of your health, understanding how your BMI works can be incredibly insightful, especially when it comes to establishing your risk of developing diseases. For example, those who are considered underweight on the BMI scale are at risk of developing anaemia, and Osteoporosis, whereas those who are considered overweight run the risk of later developing Cardiovascular diseases, Type 2 Diabetes, and certain types of cancers, and high blood pressure.
However, you should keep in mind that the BMI calculator shouldn’t be used as an end-all, be-all solution when it comes to making healthier choices. Unfortunately, the BMI calculator doesn’t take into account your muscle mass – all of which may influence your dietary needs and lifestyle choices. It also doesn’t factor in if you’re pregnant, as it doesn’t account for a growing baby. However, mothers looking to get pregnant should try to be at a healthy BMI before trying to conceive.
BMI Formulas
As mentioned earlier, BMI is ranked into four different categories: underweight, healthy weight, overweight, and obese. Here’s a deeper breakdown of what each of these categories means:
- Underweight: BMI 18.5 or under.
- Healthy weight: BMI between 18.6 and 24.9
- Overweight: BMI between 25 and 29.9
- Obese: BMI between 30 and 39.9
If you reside in the Ireland or the UK, you’ll use the following formula to determine your BMI:
your weight (in pounds) ÷ your height (in inches squared) x a factor of 703. So, let’s go back to our example from earlier: your weight is 210 ÷ 3,844 (your total height, squared) x 703 = 38.4.
BMI for Men and Women
If you’re looking to figure out your BMI category, you should check out a BMI chart. Usually, you can find your height and weight and it will give you a calculation of what your BMI is. Adults age 20 and over are calculated the same no matter their age or sex, with no other factors are brought into consideration. With children and teenagers, it’s a little different, but we’ll get into that later.
It’s important to remember that we tend to have less muscle as we age, so BMI calculations may be slightly off the older we get since they’re likely to underestimate the older adult’s body weight. Furthermore, professional athletes may have a high BMI on account of their muscles, despite not having much body fat.
Like previously mentioned, BMI charts don’t adjust for things like gender, age, etc., so just because you might fall into one category of BMI, doesn’t mean your BMI won’t affect your health in one way or another. For example, it’s been shown that Caucasians, Asians, African Americans, and Hispanics can be affected by diabetes at different BMIs.
BMI for Kids
Children and teenagers under the age of 20 have their BMIs calculated the same way, but there are considerations for weight as it relates to sex and age. BMI is not a perfect assessment of your child’s health. Many things influence their weight, including environment, physical activity, genetics, height, and metabolism. Due to these many other factors, BMI on a child is generally considered a poor way to assess their health and body composition. If your child’s BMI comes up in one category, chances are, it’ll move into another category with some growing as long as they can maintain the weight.
How Can I Calculate My BMI?
Besides seeing a physician who will be able to assess all of your variables, there are a number of excellent BMI calculators available online. Our favourite is My BMI Calculator Ireland. It’s fairly straightforward and easy to use. Just enter your height and weight and it calculates your BMI and what category you fall under.
