BODY MASS INDEX
BMI is a screening tool used to evaluate your body fat. It provides a category based on the range of body fat percentage i.e. underweight, normal weight, overweight, obese or morbid obese for their height. If your BMI falls in the category of underweight or you exceed from normal weight category (overweight, or above) it’s a time for you to keep a check on your health.The chance of health risk may increase significantly, if you find your BMI out from the healthy range.
HOW TO CALCULATE BMI
You can calculate BMI on your own by taking accurate readings of anthropometric measurements required, later applying it to the BMI formula. Various Online available calculators can also be used for BMI measurement.
The formula for Body Mass Index (BMI) is a statistic developed by a scientist named Adolphe Quetelet in the year 1900’s. This formula was developed to obtain the Body Mass of human beings. This same formula is used to evaluate the body mass of a men, women or a child. The result obtained is in kilograms by meters squared or kg/m2.
BMI Formula = Weight in kilograms/ Height in meter2
RELIABILITY OF BMI
You cannot consider BMI as a perfect, or an only measure, because it does not directly assess your body fat. As an example if we look at an athlete or a muscular person their muscle and bone density is much more as compared with body fat. So the BMI calculated will be higher even without too much of fat. But as most of you are not athlete, BMI can be used as a very good gauge for evaluation of body fat levels. In order to get the detailed overview of your body an instrument named Body Composition Analyzer is used which gives the exact information about bodies fat percentage, fat free mass, total body water percentage, total body mass, muscle mass, bone mass and BMR. The instrument works on bio-electric impedance technology.
BMI RANGE
World Health Organization provided an International classification of BMI for adults. The table states that the BMI less than <18.5 falls in underweight category, 18.50-24.99 are the ones with normal, Healthy BMI category and those with >25 belongs to overweight category. Fir more specific classification checks on the table below.
| Classification | BMI (Kg/m2) |
| Underweight | 18.50 |
| Severe thickness | <16.0 |
| Moderate thickness | <16.0- 16.99 |
| Mild thickness | 17.00-18.49 |
| Normal range | 18.50-24.99 |
| Overweight | >25.00 |
| Pre obese | 25.00- 29.99 |
| Obese | >30.00 |
| Obese class I | 30.00-34.99 |
| Obese class II | 35.00-39.99 |
| Obese class III | ≥ 40.00 |
Remember: The BMI categorization values are age-independent and the same applies for both the sexes.
BMI FOR CHILDREN AND TEEN
In order to define BMI among children’s and teens, we state BMI as age and sex specific and it is often referred to as BMI for age.
HOW IS BMI CALCULATED FOR CHILDREN AND TEENS?
As in adults the measure of height and weight was done for children’s as well and the value obtained is expressed as a percentile which can be obtained from either a graph or a percentile calculator
The interpretation of the value was based on the percentile rage.
| Weight Status Category | Percentile Range |
| Underweight | <than the 5th percentile |
| Normal or Healthy Weight | 5th percentile to<than the 85th percentile |
| Overweight | 85th to <than the 95th percentile |
| Obese | ≥ to or greater than the 95th percentile |
BMI FOR ELDERLY
All the age related changes occurring in your body has an important implication on your health status and functional efficiency. Body compositions are one among the most obvious age associated change. It is generally known that your weight increases till 60 years of age and decreases gradually thereafter. Ageing is directly associated with the reduction in total and lean body mass, muscle mass also declines with age and is gradually replaced by fat mass. Loss of height occurs in elderly. The rate may be more among elderly women due to osteoporosis. Looking all these age related changes WHO classified the category of BMI specified for elderly population (65 years and above) where BMI <23 Kg/m2 is under Underweight, those with 24-20 kg/m2 were under healthy weight category and elderly with >30 Kg/m2 or above belongs to overweight category.
WHY BMI?
BMI is a measure of weight adjusted for height; the calculation is done by dividing your weight in kilograms with your height in meters squared. BMI is a non-invasive and inexpensive mean for classifying an individual into the weight category. In BMI your excess weight is measured rather than excess body fat. BMI works as an indicator to know the potential health problems. It should not be considered as a diagnostic tool for health assessment.
LIMITATIONS OF BMI
BMI has significant limitations in the assessment of the individuals
- It does not take into account the distribution of body fat.
- The measurement does not provide any information where fat is stored in body.
- The percentage of Fat mass is not distinguished from lean body mass, and this may be underestimated for older adults, and overestimated in athletes or those with a muscular build (e.g. athletes).
- BMI rely on accuracy of reported height
- BMI gets affected by shifts in fluid weight
- BMI is influenced by age and gender