Introduction to BMI

Body Mass Index (BMI) is widely used as an indicator of body fat content. Your weight alone is not sufficient to establish if you are in a healthy weight range. For example, a tall but slender person can weigh more than a short but plump individual. But the former may enjoy better health as long as their weight is suitable for their height. The ideal weight is also likely to differ for men and women of similar heights.

How then do you know whether you fall in the healthy weight range or not? Your BMI solves this confusion. It correlates your weight with your height and evaluates whether your weight is appropriate for your stature. You can use a BMI calculator to find out your BMI.

Although not an exact measurement of body fat percentage, in most cases, BMI is a reliable tool for establishing risk levels for illnesses, especially ailments related to excess body fat. Many healthcare professionals use BMI to determine effective doses for medicines. Often people with a higher BMI need higher doses. Hence, it is crucial to be aware of your BMI to ensure your overall wellness.

How to calculate BMI

Imperial System

BMI = weight (lb) ÷ (height (inches)) 2 × 703

Example:
For a 160-pound, 5’8” (68”) individual weighing 75 kg,
BMI = (160/ 68*68) * 703 = (160/4624) * 703 = 24.3

International System of Units (SI)

BMI = weight (kg) ÷ (height (m))2

Example:
For a 177 cm (1.77 m) individual weighing 75 kg,
BMI = 75 / (1.77 * 1.77) = 75/ 3.13 = 23.96

What are the health risks related to being overweight?

Excess weight brings with it countless health complications, some of which can be fatal. A higher BMI than average (over 25) is associated with increased risks for diseases like:

• Type 2 diabetes
• Heart conditions
• Higher levels of LDL cholesterol and lower count of HDL cholesterol in the blood, increasing chances of coronary artery diseases and heart attacks
• High triglycerides
• Stroke
• High blood pressure
• Gall bladder-related complications
• Insulin resistance

• Osteoarthritis or breakdown of joint cartilage leading to painful joints
• Sleep apnea or intermittent breathing obstruction during sleep
• Atherosclerosis or building up of cholesterol deposits (plaques) in blood vessels (arteries)
• Skin health problems like skin tags, darkening of the skin

• Breathing trouble
• Hernia
• Varicose veins
• Cataract
• Gout
• Stress incontinence or urge to urinate frequently
• Certain types of cancer (breast, colon, endometrial, gall bladder, kidney, liver)
• Clinical depression and other mental health issues
• Poly-cystic ovarian disease in women leading to reduced fertility and other menstrual irregularities

What are the risks of being underweight?

Having a BMI below 18.5 is also fraught with health risks, such as the ones listed below:

• Vitamin deficiencies
• Anaemia (low red blood cell count and hence reduced capacity to carry oxygen)
• Diminished immunity or the ability to ward off infections
• Osteoporosis or brittle bones that break easily

• Malnutrition
• Developmental delays in children
• Hormonal imbalances
• Disruptions in women’s menstrual cycle causing complications in conception

Being underweight can also be an indication of underlying health conditions like anorexia. Hence, if your BMI calculator shows a value matching the underweight category, you should consult a medical professional.

Normal Range of BMI

In children, body fat content changes with age. It is also normal for teenage girls to have more body fat than boys. BMI calculation for children follows the sameformula as adults. But the value is then plotted on standard gender-specific BMI-for-age percentile charts for children. It determines the child’s weight status compared to children of the same gender and age.

For example, a 25th percentile BMI for a 6-year old female child would indicate that the child’s weight is higher than 25% of girls aged 6.