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BMI Doesn't Tell You Everything About Your Health and Weight

BMI Doesn't Tell You Everything About Your Health and Weight
Dr. Constance Odom, MD Picture of Dr. Constance Odom, MD

Medically reviewed by

Written by our editorial team.

Last Edited 8 min read

Your BMI or Body Mass Index is a method of measuring obesity and it is used as a quick way to determine different weight ranges that are classified in 4 categories: Underweight, Normal Weight, Overweight and Obese. Underweight is classified as a BMI of under 18.5, Normal Weight is classified as a BMI between 18.5 and 24.9, Overweight is classified as a BMI between 25 and 29.9 and Obese is classified as any BMI 30 or higher. BMI is based on a person's height and weight, and many BMI calculators do not compensate for characteristics like sex, age, etc. Although BMI calculations can provide some quick information about a person's general health, they are actually quite limited in the information that they can provide and BMI doesn't tell you everything about your health.

BMI calculations don't include body fat measurements

One of the most glaring issues with BMI calculations is the fact that they don't include body fat measurements. Body fat percentages are incredibly important for most people to know, and even an approximation of your body fat percentage can tell you a lot about your health and where you might need to focus in terms of your exercise and dieting goals. BMI doesn't give any specifics about body fat, meaning that you may have a relatively low BMI that fits in the range of "€œnormal weight"€, but you might be unhealthy by having a high body fat percentage even though your weight is close to the normal range.

You can't use BMI alone to determine your health

Because of the fact that BMI doesn't track body fat, it allows a great deal of inaccuracy when it comes to use it as a sole determinate of health. For example, a male with a body fat over 20 percent or a female with body fat over 30 percent carry a relatively similar risk of chronic illnesses, even though their weights may fall within a normal BMI range. A person who looks overweight may have a higher BMI but also carry a similar risk of chronic illnesses as those who fall with a normal BMI range but have a high body fat percentage. So body fat plays into the equation and it's important to track it as often as you can.

It's essential to measure and keep track of your body fat percentage

Measuring and keeping track of your body fat percentage is essential along with your weight, and although it's easy to overlook doing this you need to keep track of it regularly. Your body fat percentage can change even though your weight may stay the same, and it can change as the result of changes in your diet or changes in your physical activity level. You can use a wide range of different methods to calculate your body fat percentage, such as calipers or the dunk tank method, but you should be sure to calculate it with your BMI and keep track of changes. You don't have to keep track of it as often as you do with your weight.

Body fat changes are more gradual

The reason why you don't need to track body fat quite as often is the fact that body fat changes tend to occur more gradually than weight changes. When your weight changes up or down quickly over a period of a few days or weeks, it is beneficial to keep track of these changes along with monitoring any dietary changes or other lifestyle changes that may have occurred recently. If you track your body fat once every few weeks or so you will notice that it is difficult to add or decrease your body fat because it takes a significant amount of effort just to change your body fat by one percentage point, but the ramifications are far greater

Decreasing your body fat is strong correlated with a lower risk of chronic illnesses. For example, there are many people who carry excess midsection weight and who have a sedentary lifestyle. Even though these people may fall within a normal BMI range, their body fat may be higher than 20 percent (for males) or 30 percent (for females), which as previously mentioned carries the risk for illnesses like diabetes, heart disease, high blood pressure and other health problems. For those with a normal BMI but with a high body fat percentage, their focus should not just be on decreasing their weight but also doing things to reduce their body fat such as reducing their carbohydrate intake, consumption of simple sugars, exercising and more.

BMI can be very misleading for active people and athletes

Another problem with BMI calculations is the fact that they do not compensate for athletes and others who put on weight from muscle. This can be very misleading for athletes and active people who perform resistance training regularly, as their BMI calculation may be considered to be "€œoverweight"€ in spite of having a low body fat percentage. This is why BMI calculations are rarely used by professional athletes and even those who exercise frequently should be cautious about using them for any sort of health determination. It's better to meet with a medical provider to discuss your health goals rather than using any sort of weight loss calculation, if you are active or trying to determine what a healthier weight is for your particular lifestyle.

BMI does offer important general information about your health

BMI does offer important information for many people and it can give you a warning about your health that you may need to further investigate. Most people who have a BMI that estimates their weight as "€œoverweight"€ will likely need to take steps to reduce their weight in order to reduce their risk of chronic illnesses and improve their overall health. BMI offers a fast way for someone to figure out whether or not their weight may be healthy based on a few factors, and although losing weight has health benefits for people of all ages and both sexes, it's important to take it a step further and calculate your body fat percentage, especially as you start to reach your target weight.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your physician about the risks and benefits of any treatment. Nu Image Medical may not offer the medications or services mentioned in this article.