Healthy and Unhealthy BMI Values

You can calculate your BMI using an online calculator.

BMI and Your Health

Most studies on BMI agree on two key points:

• People with obesity or extreme obesity face a much higher risk of dying from any cause.
• Those who are underweight also have a higher risk of death, often due to underlying health conditions like heart disease, lung disease, cancer, or infections that typically cause weight loss as they worsen.

If there is a controversy, it centers around individuals with overweight status, but not obesity. This includes those with BMI scores a little over 25. Most studies have shown increased medical risk even with this mild state of being overweight, but a few studies show a slightly lower risk for these individuals.

Several explanations for this apparent discrepancy have been suggested. The one that has the most traction is the idea that BMI is not a good measurement for people who are extremely fit.

The Obesity Paradox

Since the early 2000s, studies have shown that people with heart disease in the overweight BMI category tend to have better survival rates. Larger reviews and meta-analyses support this observation.

This phenomenon, where individuals with above-normal BMI may experience lower cardiovascular mortality, is known as the obesity paradox.

What the Research Says

In a 2015 study published in the journal Heart, researchers analyzed data from 89 studies, involving over 1.3 million people with coronary artery disease. They found that underweight individuals had the highest short- and long-term mortality risk (over three years).

Participants with an overweight or obese BMI had lower short- and long-term mortality risk compared to those with a normal BMI. However, the risk for those with obesity increased after five years.

A 2018 study evaluated 65 prior studies involving 865,774 people who underwent coronary artery bypass graft surgery or percutaneous coronary intervention. It found that, compared to normal-weight individuals, all-cause mortality was higher for underweight people and lower for those who were overweight, obese, or severely obese. Notably, being in the overweight BMI category was linked to the lowest risk of major heart-related events.

How Well Does BMI Measure Risk?

Why does the obesity paradox exist? Current thinking is that BMI is an insufficient measure of a person’s cardiovascular risk since it fails to take into account a person’s muscle mass and overall cardiorespiratory fitness.

On the other hand, people who may formerly have been overweight and go on to develop heart disease often develop muscle wasting, and their BMIs may drop back into the normal range.

Because of this, BMI by itself may give a misleading picture of a person’s cardiovascular health.

Factors That Determine if Your BMI Is Healthy

Some of the variables that can determine whether an elevated BMI is still healthy for you to include:

• Fitness level: If you follow a regular exercise routine and you have good muscle mass, you may have a higher BMI. A high BMI in very fit people is not associated with greater health risks.
• Age: A younger adult may have less body fat than an older adult with the same BMI.
• Sex: Females tend to have more body fat than males, even when they have the same BMI.
• Ethnicity: People of different ethnicities have variations in frame size, fat distribution, and so on, which affects what is considered a “normal” BMI for each group.

The range of healthy to unhealthy BMI may not be accurate for everyone. This is why many experts now say that, instead of relying on BMI to determine whether weight is contributing to cardiovascular risk, abdominal fat should be the greater focus.

Abdominal Fat and BMI

Having too much fat—specifically, too much fat in your midsection—places significant metabolic stress on the cardiovascular system and increases the risk of cardiovascular disease.

While the BMI score is sometimes useful and easier to measure, the waist-to-hip ratio is probably the more important index of cardiovascular risk.

So, if you have a BMI of 27, for example, you are in the “overweight” category. Before drawing conclusions about this, answer this one question: Is your waist size less than your hip size?

• If yes, then the “excess” weight contributing to your BMI score is likely muscle and not fat.
• If no, you likely have centrally deposited fat, which is cause for concern.

How Can I Lower My BMI?

You can work to lower your BMI by changing the way you eat and staying active. Focus on plant-based foods like fruits, vegetables, and whole grains, and avoid foods that contain a lot of unhealthy fats and added sugar.

Try to get at least 30 minutes of exercise a day, five days a week. This can be as simple as a brisk walk or a bike ride.

Avoid crash diets and fad diets. These may work for short-term weight loss, but sustainable change involves making permanent changes to your activity levels and the way you eat.