Body Mass Index: Advantages & Limitations - Why BMI Is Not Accurate Body Fat Measure

The ideal weight for a person of a certain height, age, and sex will vary considerably for most individuals, and should be used as an indicator only. It should not be used to determine if one's weight is over or under the ideal for that person.

Body Mass Index or BMI is a simple weight measuring system that is used for determining the level of body fat an individual has. A BMI reading provides a reasonably accurate indication of the amount of body fat present. Doctors often use BMI to ascertain if a patient’s fat level put him/her at increased risk to various health conditions.

How to calculate your BMI

Calculating BMI is fairly easy. First, determine your weight in pounds and your height in inches. Then, divide your weight by the square of your height, and multiply the resulting number by 703. The reading you get after doing all this is your BMI. The formula for calculating BMI is: weight in pounds/ (height in inches) ² X 703 For instance, if your weight is 150 pounds and height is 72 inches, your BMI is: 150/ (72)² X 703 = 20.3 If math is not your thing, simply log on to the Internet, locate an online BMI calculator, and use it to calculate your BMI.

Advantages of BMI

The advantages of using BMI to calculate body fat are: a. It is easy to use b. It is free unlike other body fat measurement methods like underwater weighing and dual energy X-ray absorptiometry c. It provides reasonably accurate body fat readings

Deciphering BMI reading

Calculating BMI is only half the job, the other half is to understand what a BMI reading means. Given below is the BMI index and its significance.

• BMI reading less than (<) 18.5 – Indicates you are underweight
• BMI reading between 18.5 to 24.9 – Indicates your weight is normal, and there is no need to lose any weight
• BMI reading between 25 to 29.9 – Indicates you are overweight. If you also have other risk factors like high cholesterol or high blood pressure, you need to lose weight
• BMI reading greater than (>) 30 – Indicates you are obese, and must lose weight to reduce your risk of various health conditions

Understanding the risks associated with a high BMI reading

A high BMI reading indicates that you are overweight, which in turn is a significant risk factor for various health conditions such as high blood pressure, high cholesterol, type 2 diabetes, heart disease, stroke, sleep apnea, etc. That is why health experts ask people with a high BMI to lose weight.

Tips to lose weight

Needless to say, if your BMI is high, you must make efforts to lose weight. To do so, you need a holistic program based on healthy diet by following a regime of weight management recipes and regular exercise. The following tips will also come handy if you’ve decided to make a committed effort to shed the extra pounds.

• Stay away from fancy diet plans – Let us get one thing clear: there is no instant-weight-loss mechanism. Yes, man has developed instant noodles and instant coffee, but a mechanism that produces instant weight loss has been out of bounds. So, don’t waste your money and time on diet plans or other weight loss products that promise magical weight loss in short period of time. They simply don’t work, and cannot sustain whatever weight loss they induce in the initial few days.
• The more weight you need to lose, the harder you have to work – sensible eating and weight loss is not hard once you accept that it is not a walk in the park. You must observe self-discipline and work diligently toward it. With that said, it is also not very hard. Don’t believe anyone who tells you that it is unachievable. Millions of people every year lose weight, and you too can do it.
• Knowledge is the key – Health experts believe that most weight loss enthusiasts fail not because of lack of motivation or effort, but due to faulty weight loss plans. Knowing what to eat, when to eat, what type of exercises to perform, etc. is absolutely essential if you want to lose weight.
• Keep realistic goals – Lastly, it is necessary that you keep realistic weight loss goals. Health experts recommend losing weight at a rate of 5-8 pounds a month is an achievable and effective weight loss goal, and one to which most people can stick for a long time. To lose 5-8 pounds a month, you will need to reduce your total daily calorie intake by 500-1000 calories.

Limitations of BMI

It is true that BMI is accepted as a pretty good indicator of body fat, but it does have some limitations, and you need to be aware of them.

• BMI does not calculate body fat directly – According to the Center for Disease Control and Prevention, a Body Mass Index (BMI) test does not calculate body fat directly. Instead, it calculates body fat indirectly. With that said, there is complete consensus among health experts and doctors that a BMI test gives a fair indication of body fat levels. The tests that measure body fat directly is underwater weighing and dual X-ray absorptiometry. However, unlike a BMI test, these tests can be expensive.
• BMI varies among women, men, and people of different age groups ¬– According to the Center for Disease Control and Prevention, at the same BMI, men have less body fat than women. Similarly, at the same BMI, people who are active have less body fat than people who lead a sedentary life style. This variation is also observed in people of different age groups. At the same BMI, young people have less body fat in comparison to their older counterparts.
• BMI takes into account the height and weight of the individual. It does not take into account the specific contribution of one's muscles, fat, and bones to one's body weight. A body builder may have a BMI of 30 alhtough he is very lean. This is because BMI does not take into account that a body builder's weight of 250 pounds is mainly muscles. An obese person that weighs 250 lb and is as tall as the bodybuilder is, will have the same BMI!

Author Pete Markovic writes for GoodHealthWord.com