What is BMI?
What is BMI and what is BMI for?
BMI stands for Body Mass Index. It is a measure traditionally used by medical professionals to determine if an individual's weight is within the predefined limits of a healthy weight for their height. It is known that being overweight places an individual at greater risk of developing a large range of medical conditions, such as heart disease, stroke, type 2 diabetes, some types of cancer, high blood pressure (hypertension) and kidney disease. Likewise being underweight can increase a persons risk of health problems, for example, brittle bones (osteoporosis), absent periods in women (amenorrhoea) and iron deficiency (anaemia).
Some people mistakenly think BMI measures the percentage of body fat a person is carrying, whereas it simply provides a measure, which attempts to describe their body mass in relation to their height.
The principal idea behind BMI is that by losing or gaining weight you will reach a healthy BMI and put yourself into a lower risk group. Unfortunately, body composition is not quite as simple as that with BMI not taking the percentage of lean body mass into account during calculation.
How do you find your BMI?
To calculate your BMI divide your weight (in kilograms) by your height (in metres) squared. The BBC provides an online calculator which will do this for you. You can also easily read your measurement from a BMI chart, like this one provided by Caloriecounting.co.uk.
BMI measurements are divided into several categories:
- BMI Less than 20 — Under Weight
- BMI 20-25 — Normal Weight
- BMI 25-30 — Over Weight
- BMI 30-40 — Obese
- BMI Over 40 — Severely Obese
BMI Limitations and Myths
The myth of BMI is that losing or gaining weight will place you in a lower risk group, this is because it is calculated using your weight and height. The problem with this is that when a person loses or gains weight it is not a direct measure of their percentage bodyfat, which is the important figure, it is a combined measure which also includes the water and muscle in their body.
BMI is not a reliable measure when it comes to people with athletic or muscular builds, especially people who lift weights on a regular basis. In these cases BMI can give you a higher BMI even if you have a healthy level of body fat. The BMI chart is also not accurate for pregnant or breastfeeding women.
What is a Healthy Weight?
A healthy weight could be defined by a number but just as equally by a feeling. When you live a healthy lifestyle, eating a balanced diet, containing plenty of fruit and vegetables, adequate protein and carbohydrates and enough good sources of essential fatty acids coupled with various forms of exercise, your body will level out at a healthy weight. You will know you have reached that weight when you feel good within yourself. If you feel you need to lose weight remember that slow and steady is the best approach. To lose 1lb per week you need to reduce your daily calorie intake by approximately 500 calories.
Are you interested in tips that will help you lose weight in a healthy way?
The Final Word
It is now widely accepted that measuring your waist is a good way of discovering if you are at higher risk of developing various health conditions. Generally you should aim to not have a waist measurement greater than half your height e.g. if your height is 5 ft 5 inches then you waist should not be more than 32.5 inches. Ideally, you should use a range of measurements to ascertain if you are at a healthy weight.
The BMI charts referenced above are calculated for adults with separate charts being available for children’s weight and heights. Although after reading the limitations of BMI it would be prudent to reconsider putting too much faith in these measurements as an indication of your children's health either.