IF you've ever been even slightly conscious or curious about your weight, then chances are that you have heard the term BMI being tossed around. You may have gathered that it has something to do with your 'weight for your height', but do you know what yours is? And what does it mean anyway?
“Body mass index (BMI) is the ratio of a person's weight to their height that is used to classify their weight status,” explains registered nutritionist and university lecturer Vanessa White-Barrow. “It is calculated by dividing your weight by the square of your height.”
To find your correct BMI, ensure that your weight is in kilogrammes. Then divide that number by your height in meters squared. If your height has been measured in centimetres, divide by 100 to convert this to meters. The result of that equation is your BMI. For example, an adult who is 5'10” and weighs 173 pounds (78.47kg) will have a BMI of 24.82.
White-Barrow, in explaining that BMI measurements are important in helping medical professionals assess whether someone is too skinny or fat for their height, interprets BMI readings.
“A healthy BMI is considered to be anywhere between 18.5 and 24.9 kgm-2,” she says. “A BMI that is less than 18.5 kgm-2 is considered underweight, while anywhere between 25 and 29.9kgm-2 is overweight. Thirty and above are classified as obese.”
If you're good at math you would have worked out your BMI on your own by now, or you may have popped your weight and height into a free BMI calculator online to help you out. But now that you know your reading, what can you do about it?
“For people with an extremely high BMI, dietary recommendations include limiting consumption of fats and foods/beverages that contain added sugars, and replacing high-fat meats with lean meats such as fish and chicken breast,” the nutritionist instructs. “Also, consume two to three servings of green leafy and yellow vegetables daily; and replace refined and ultra-processed cereals such as flour, with whole grain/provisions that provide fibre, which also helps to increase satiety and reduce tendency to overeat.”
She prescribes that people with extremely low BMI find healthy ways to bulk up.
“They can increase weight by eating foods from all food groups, especially fruits and vegetables, to ensure they meet their micronutrient (vitamins and minerals) needs. They should also balance their calorie intake with their daily physical activity,” she explains.
She is quick to point out that BMI, while helpful, cannot give a wholesome representation of how much of a person's weight is actually fat, so other factors must be taken into consideration.
“BMI is not appropriate for classifying the body weight of muscular people such as athletes,” she notes. “The body weight of such people is mostly muscle, which lowers their health risk.”
Other factors such as age and pregnancy may also skew BMI readings. White-Barrow recommends that while your BMI can give you a fairly good indication of how healthy your weight is for your height, you take a holistic approach to managing your weight.
“Apart from diet, other factors to consider for healthy weight management/nutritional health include physical activity frequency, duration and intensity; sleep duration and stress management,” she says.