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Understanding Body Mass Index: What Is It And How Is It Calculated?

understanding BMI
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What is BMI?

BMI or Body Mass Index is the measurement of a person’s weight in relation to the height. The figure gives an approximate measurement of the amount of fat the person has. Since the score is directly proportional to the amount of fat, a high figure corresponds to a higher amount of fat the person has.

  • BMI of 18.5 or lesser- means the person is underweight
  • BMI of 18.5- 24.9- means the person is healthy
  • BMI of 25-29.9 – means the person is overweight
  • BMI of 30 or more – means the person is obese


Body Mass Index (BMI) Weight Status
Less than 18.5 Underweight
18.5-24.9 Healthy
25.0-29.9 Overweight
30.0 or more Obese


In most cases, BMI proves to be a reliable tool to measure body fat percentage. It is a simple calculation that can be done with a mathematical formula and anyone can do it.

How to Calculate Body Mass Index?

To calculate the BMI of an individual, the following BMI formula can be used.

BMI= Weight in kilograms/height in meters squared

There are many charts available online and in pharmacy shops that plot weight with respect to height and provide the BMI figures for individuals.

The Relevance of Body Mass Index

BMI helps to decide the place of the individual in the health spectrum. Since it gives an approximate value of the amount of fat a person has, it helps doctors and other people in the healthcare field to screen individuals who are obese or overweight. Corresponding to this, medical risks associated with the two conditions can be assessed.

Some conditions associated with being overweight or obese are:

  • High blood pressure
  • Heart disease
  • High amount of cholesterol
  • Stroke
  • Diabetes
  • Cancers
  • Gallbladder disease
  • Snoring and sleep apnea
  • Osteoarthritis and joint problems
  • Premature death

However, one must remember that BMI is just one aspect when assessing health risks. Other factors that need to be taken into consideration are genetic history, age, gender, levels of physical activity, blood sugar levels, smoking habits, waist circumference, etc.

In most cases, BMI provides a comprehensive measure of obesity and health risks associated with that. There are some areas where it falters, though. It doesn’t take into consideration the amount of bone, fat, muscle mass and mass of other tissues.

For example, someone might weigh more because of a high amount of muscle mass and fall in the overweight category. In reality, they are quite fit and healthy. So, two people can have the same BMI score in which one is very healthy and has a very less body fat percentage and another may be the opposite with a high amount of fat in their body. On the other hand, an old person can fall in the normal BMI but still have a high amount of body fat percentage. Children, adolescents, pregnant women, persons with smaller or larger skeletal frames, and muscular individuals will have a varying BMI score which may or may not correspond to the amount of body fat they have. Their BMI scores need to be interpreted differently.

Limitations of Body Mass Index

While BMI can accurately draw connections between body fat, there are certain limitations that it suffers from. For example,

  • Men have a lesser amount of body fat than women
  • Younger adults have lesser body fat than older people
  • Trained athletes and sportspeople have higher BMI

How to Improve Your BMI?

If your BMI falls in any category apart from ‘healthy’, you could do the following to bring it to the healthy range.

1. Get Active

Establishing an exercise routine will help to bring down the fat percentage in your body. Regular workout sessions will improve your appearance and your mood apart from bringing down your weight. Weight training and high-intensity interval training are great options to reduce body fat. Make small but potent changes to your routine. Walk to work or take the stairs instead of the lift. Read more about the health benefits of exercise

2. Eat Consciously

Diet contributes to 80% of our weight gain or weight loss. Make healthy eating a lifestyle change and not a fad that you have to follow for a short while. Be consistent and disciplined in your food choices and have an occasional cheat day but not too often. Mindful eating is half the battle won. Stock up your meal on protein and reduce your carbohydrate intake. Maintain a food diary to document whatever you eat. If possible, consult a dietician and stick to the diet plan that she or he creates.

3. Get Enough Sleep

Your body needs enough rest to have a healthy metabolism. Get enough shuteye to keep your weight in check. Adopt healthy sleeping habits so your body knows when it is time to switch off and go to sleep. Do not use any gadgets for an hour before sleeping. Try to shift the television out of the bedroom. Hit the sack at the same time every night and refrain from having any caffeine or alcohol before bedtime.

4. Celebrate Your Progress

Monitor your progress from the day you started. A weekly or a monthly review helps to keep yourself motivated and to correct the areas where you could be lacking. Celebrate your successes. There are many apps that help monitor various aspects of your health- from healthy eating and recording meals to recording the workouts.

5. Monitor Your Activity Level

Research says that monitoring your activity levels will help give you a clear picture of how much you actually move. We might think we walk a lot but when we record our activity levels through gadgets and apps, we realize we have overestimated our activity levels.

6. Go for Regular Weigh-ins

Weigh yourself regularly. This helps you to stick to your goal and provides immediate feedback on your efforts. Weigh yourself once a week at the same time.

7. Consistency is the Key

Instead of going all out with your workout schedules and eating healthy only for a month and then relapsing into your old, unhealthy lifestyle, it is better to stay consistent with small changes. Begin with small steps and work your way up towards a regular, consistent healthy living. This way you program your mind to accept the small changes and get settled in the new routines. Every week or month, replace a bad habit with a new, healthier ones.


While it is important to calculate BMI and figure out where you land in the health spectrum, a too high or too low reading should not deter you. Age, gender, muscle mass and bone weight all contribute toward the reading and adjustments must be made accordingly. Ensure that you eat a clean diet and follow a regular exercise regimen to keep yourself healthy.

Read More: 5 Simple Ways to Stay Fit

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