Body mass index or BMI is a term that is used often in the fitness community. It is nothing but a technique to estimate the amount of body fat by using your height and weight measurements. BMI was initially used by health care professionals to identify the physical health of their patients, but BMI is now used by people to track their health and fitness goals. In this blog, we will understand what BMI is, how it is calculated and what is a healthy BMI range.
What is BMI?
BMI or body mass index is a technique used to measure an individual’s body weight relative to their height. It is calculated by measuring a person’s weight in kilograms by the square of their height in meters (kg/m²). BMI helps to categorised individuals into three categories as underweight, normal weight, overweight, or obese, providing an indication of potential health risks related to body weight, though it doesn’t account for factors like muscle mass.
How to Calculate BMI?
Here is a simple BMI calculator:
- Measure your weight in kilograms (kg).
- Measure your height in meters (m).
- Square your height (multiply your height by itself).
- Divide your weight by the square of your height.
The formula is:
BMI = weight (kg) ÷ height² (m²)
For example, if you weigh 70 kg and are 1.75 meters tall:
- 75 × 1.75 = 3.0625
- 70 ÷ 3.0625 = 22.86 BMI.
This would classify you as having a “Normal weight” according to BMI categories.
What are BMI Ranges?
| Underweight | Less than 18.5 |
| Optimum range | 18.5 to 24.9 |
| Overweight | 25 to 29.9 |
| Class 1 obesity | 30 to 34.9 |
| Class 2 obesity | 35 to 39.9 |
| Class 3 obesity | More than 40 |
Health Implications of Low BMI
If a person has a BMI less than 18.5 then that person is considered as underweight and is at the risk of developing the following conditions:
- Malnutrition
- Anemia
- Weakened immune system, which could lead to more frequent infections and illnesses.
- Osteoporosis
- Infertility
Health Implications of High BMI
If a person has a BMI of more than 25 then that person is considered overweight and is at the risk of developing the following conditions:
- Heart disease.
- High blood pressure (hypertension).
- Type 2 diabetes.
- Gallstones
- Osteoarthritis
- Sleep apnea.
- Certain cancers, including colon, breast, endometrial and gallbladder.
- Depression and other mental health conditions.
Body Mass Index for Children
Although the formula for calculating BMI for children remains the same the interpretation is different for people under the age of 20. BMI for all age groups, the implications for children and adolescents can vary depending on age and gender.
For children Centers for Disease Control and Prevention (CDC) uses age growth charts to show BMI as a percentile ranking. A child’s BMI in relation to other kids their own age and gender is expressed by each percentile. For instance, if a child’s BMI was at or above the 95th percentile, they would be classified as obese. This indicates that their body fat percentage is higher than that of 95% of kids in the same age and gender group.
The following parameters are used to measure BMI for children
| Percentile | Weight Status |
| Below 5th | Underweight |
| 5th to 85th | Normal or healthy weight |
| 85th to 95th | Overweight |
| 95th and above | Obese |
Conclusion
We hope this blog has helped you understand what body mass index is, how to calculate it and what are the health implications of low and high BMI. BMI is a tool that you can use to assess your risk for certain health conditions. It is important to understand BMI is not always an accurate measurement of body fatness and is not the sole determiner of your general health. Please talk to a health care provider to know more about your body composition.
FAQs
1. What is body mass index and how is it calculated?
Body mass index is a tool that measures a person’s body fat by measuring weight and height of the person.
2. What is a normal BMI?
BMI ranging between 18.5 to 24.9 is a normal BMI
3. What is a good BMI for my age?
To know a good BMI for your age, ask for a BMI chart at a doctor’s clinic
4. What is the formula for BMI?
The formula for BMI is BMI = weight (kg) ÷ height² (m²)
5. How do you calculate your BMI step by step?
To calculate BMI step by step
- Measure your weight in kilograms (kg).
- Measure your height in meters (m).
- Square your height (multiply your height by itself).
- Divide your weight by the square of your height.
The formula is:
BMI = weight (kg) ÷ height² (m²)
