Why A Healthy BMI Might Not Mean A Healthy Weight


The standard measure for determining healthy body weight is BMI or Body Mass Index. This is the accepted metric for defining underweight, normal weight, overweight as well as obesity.

BMI works by estimating the amount of body fat an individual carries given their height and weight. These measurements assort individuals with BMI readings below 18.5 indicating that a person is underweight. A reading between 18.5 and 24.9 indicates that the person is in the normal range and a BMI exceeding 30 or above is considered as being overweight.

BMI chart

How Can BMI Be Misleading?

There are a few distinct issues about accuracy with BMI. Obesity experts categorize these as the following

1. BMI does not give an accurate estimate of the body fat a person carries around.

To elaborate, BMI does not discriminate between muscle and fat. BMI readings do not differentiate between the different types of fats, but each type of fat can have a varying metabolic effect on health. For instance, one area that has proved very problematic is that BMI does not take consider where fat gets stored in the body.

Visceral fat, also known as belly fat is way more dangerous than the fat simply positioned under the skin. It coats organs and even fairly thin individuals may have elevated levels of visceral fat. This means they may be regarded as healthy using BMI standards, however, internally these people may be at a greater risk of developing health issues related to weight gain.

2. BMI readings can vary significantly based on gender.

A male or female patient with an equal body fat percentage can have very different BMIs. This also means that two individuals with the same BMI could have very different body compositions.

Women typically have a higher percentage of body fat than men whereas men are more likely to have greater muscle mass. For women, essential body fat or the fat required to function normally accounts for 10-13% of a woman’s total body fat. Men, on the other hand, only need or have 2-5% essential body fat.

Likewise, athletes or bodybuilders have more muscle than non-athletic individuals while older adults have more body fat than younger people. All these differences can make BMI readings seem very ambiguous.

3. Having a high BMI does not mean a person is overweight or obese.

A person can exhibit a high BMI despite having insignificant amounts of body fat, such as being male and muscular. In such cases, the muscle tissue pushes up their weight.

On the other end of the spectrum individuals who are overweight may not necessarily be any less healthy or at a higher risk to suffer from mortality than others who are within a normal BMI range.

Interestingly enough, recent research also points out in the direction that in certain scenarios, a higher BMI could potentially prevent an individual from dying of kidney or heart failure along with other chronic illnesses. For instance, having more fat for someone with a chronic disease may mean supplementary energy reserves. While a lower BMI may occur from a person having a serious illness.

4. BMI does not consider waist circumference.

The location of fat on the body makes a difference to health. Belly fat or fat that accumulates in the mid-section around the waist instead of the hips puts a person at a greater risk of heart disease and type 2 diabetes. On the other hand, fat that collects on the hips and thighs is not as potentially harmful.

Alternatives to BMI

So despite having all these inconsistencies, why do doctors still use BMI to measure weight and evaluate obesity? Well, primarily this is an easy way to take measurements during a doctor’s visit. All that is required is the person’s height and weight figures, and doctors can establish whether their patient is at a low, moderate or high risk in terms of weight related chronic issues.

However, there are other better ways that can help determine body fat deposits and let medical experts know whether a person’s weight might lead to chronic health problems or not.

  • Waist size:

One of the best ways to determine body fat is to use a tape measure to go around the waist. Ideally, men should have a waist no larger than 39-40 inches whereas women should limit their waistline to a maximum of 35 inches.

The formula states that waist circumference should be less than half the height on the person.

  • Hydrostatic weighing

This method measures a person’s normal body weight outside water to their body weight while completely submerged. Using the two numbers along with the density of water, doctors calculate the person’s density and then use it to estimate their body composition.

  • Other options

Other options like MRIs and CT scans can give a more accurate picture of body composition by separating muscle from fat. However, these are costly and require more effort. Likewise, DEXA images and other scans can be used to calculate bone density but can be expensive as well.


There’s no doubt the BMI can be used as a healthy weight gauge but not as the only barometer to a healthy weight. There are other alternatives listed above that you can also look into. However sometimes the only equipment you need to see if you’re in a healthy weight zone is the mirror.

Author Bio

Jasmine author for BMIJasmine is a firm believer in adopting a healthy lifestyle and writes for FuelForMyBody.com which covers health and fitness topics. In her spare time, she enjoys going for long walks and trying out new recipes.

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