BMI: WHAT IT SAYS ABOUT YOUR HEALTH?

CONTENT

INTRODUCTION

CLASSIFICATION

BMI AND WOMEN HEALTH

LIMITATIONS OF BMI

 

INTRODUCTION

The BMI is an indirect mathematical representation of how fat or how thin we are. It uses the relationship between our weight and height to suggest how fat or thin we are and with it suggests the ideal weight for a person’s height. It is defined as the mass or weight of an individual in Kg divided by the square of the person’s height in meters and applies for people 20 years and above.

BMI= weight/Height2 (Kg/m2)

CLASSIFICATION

Using the BMI, individuals can be categorized into underweight, normal weight, overweight, and obese. WIth these, they can be advised on possible health risks associated with each categories. Although the commonest chart used is the WHO (World Health Organization) classification, many regions, especially Eastern Asia have separate charts for the classification of BMI. This is due to the relatively higher body fat content of poeple of East Asian descent, along with a tendency to develop complications of obesity at a relatively lower BMI compared to other people around the World. For the purpose of our discussion on this site, we will use the WHO classficition.

WHO CLASSIFICATION                                                                                                                             

Category BMI (kg/m2)
Very Severely Underweight Under 15
Severely Underweight 15 – 16
Underweight 16 – 18.49
Normal (healthy weight) 18.5 – 24.9
Overweight/pre-obesity            25 – 29.9       
Class I obesity 30 – 34.9
Class II obesity 35 – 39.9
Class III obesity or morbid obesity 40 and Above

                   

SINGAPORE CLASSIFICATION 

Health Risk BMI (kg/m2)
Risk of developing problems such as nutritional deficiency and osteoporosis under 18.5
Low Risk (healthy range) 18.5 – 22.9
Moderate risk of developing heart disease, high blood pressure, stroke, diabetes 23 – 27.49
High risk of developing heart disease, high blood pressure, stroke, diabetes over 27.5

 

BMI AND WOMEN HEALTH

The relationship between the BMI and various health risks can described as “U” shaped. This is because people with the lowest health risks are those who fall within a normal BMI range i.e. between 18.5 to 24.9, similar to the middle portion of the “U,” while those at the extreme ends of the BMI are associated with an increased risks of health hazards that worsens as the value gets farther away from the normal range, corresponding to the vertical arms of the “U”. Hence, the risk of a person developing various health problems increases as the value of the BMI decreases further below 18.5 or further above 25. For example, individuals with BMI lower than 18.5 who are said to be underweight are at an increased risk of various health conditons such as irregular ovulation, nutritional deficiencies, bone fractures and body weakness, which worsens as the BMI reduces while women with BMI greater than 25 are at an increased risk of cardiovascular diseases such as stroke, hypertension, heart attack and diabetes which becomes marked from 35 and above, worsening as the BMI increases. Obesity is defined by the WHO as a BMI greater than 30. To calculate your BMI, please click on BMI CHECK.

 

LIMITATIONS OF BMI

1.  Although BMI provides a simple way of measuring a person's thickness or thinness, it is however a relatively poor method of measuring the proportion of fat in an individual in    relation to his or her weight. This is because it doesn’t differentiate between muscles, bones and fat while measuring the weight of an individual. It is therefore not surprising that it   tends to overestimate fatness in tall, fit and muscular people and underestimate fatness in short, stout and chubby people.

2.  It doesn’t consider the variation in fat levels according to one’s age, sex (either male or female) and physical activity.

3. It doesn’t take into consideration the specific distribution of fat in one’s body as it relates to one’s health risks. In fact, most health hazards associated with obesity are directly attributed to excessive storage of fat around the abdomen rather than in other parts of the body. Thus different people may have different fat distribution as a result of their physique, yet they may have the same BMI, while in reality they have different health risks. BMI therefore, is better used along with other methods that specifically measure the distribution of fat in the body such as the waist hip ratio, waist height ratio, and surface based body shape index.

 

NEXT ARTICLE: WAIST HIP RATIO: WHAT IT SAYS ABOUT YOUR HEALTH?

 

REFERENCES

1.  BMI; http://www.euro.who.int/en/health-topics/disease-prevention/nutrition/a-healthy-lifestyle/body-mass-index-bmi

2.  Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. The Lancet , Volume 363 , Issue 9403 , 157 – 163

3.  "About Adult BMI | Healthy Weight | CDC". www.cdc.gov.29.08.2017.

4.  Romero-Corral, A; Somers, V K; Sierra-Johnson, J; Thomas, R J; Collazo-Clavell, M L; Korinek, J; et al. (2008). "Accuracy of body mass index in diagnosing obesity in the adult general population". International Journal of Obesity. (6): 959–66. doi:10.1038/ijo.2008.11. PMC 2877506 Freely accessible. PMID 18283284