Updated on February 16, 2024.
You may have had your body-mass index (BMI) measured at your last health screening. It’s a rough tool healthcare providers (HCPs) use to estimate the amount of fat in your body, involving a ratio of your height to your weight.
Although BMI is commonly used to indicate whether someone is overweight or underweight, it’s not the only measure used for this purpose—and it’s not a perfect measure of overall health. There’s another figure that’s arguably more useful: waist-to-height ratio (WHR). A fairly straightforward measurement involving your waistline, WHR has been endorsed by more and more HCPs in recent years.
That’s the message from research that’s been going on for decades and has amplified in recent years.
A brief history of waist measurements
In the 1950s, health researchers began to take note of the way fat was distributed throughout the body, paying attention to whether it was located in the upper or lower torso. During the 1980s and 90s, scientists noted that WHR helped predict risks of death and heart disease. Studies since then have continued to highlight the usefulness of the WHR measurement.
The higher your WHR, the larger your waist is relative to your height and the more weight you carry around your midsection.
- A healthy WHR is generally around 0.4 to 0.49.
- A ratio of 0.5 to 0.59 indicates an increased risk of health issues.
- A ratio higher than 0.6 indicates obesity and an even greater risk of health issues.
Over the years, many health experts have used fruit metaphors to help people visualize WHR. Generally speaking, people with rounder, apple-shaped bodies tend to have more fat located around their bellies, and thus a larger waistline and higher WHR. People with pear-shaped bodies, have comparatively thinner waists (and lower WHR) with more fat located lower down in the body, around the hips, buttocks, and upper thighs.
Reasons to be wary of BMI
WHR is an effective way to measure one’s body composition and overall health, but BMI been in use longer and has persisted as a go-to measure.
To get your BMI, you divide your weight in pounds by your height in inches squared, then multiply by 703. (You can also use an online adult BMI calculator provided by the Centers for Disease Control and Prevention.)
Your final BMI calculation places you in one of five groups:
- A BMI of below 18.5 means you’re considered underweight
- Between 18.5 to 24.9 is considered a healthy weight
- Between 25 and 29.9 is considered overweight
- Between 30 and 39.9 is considered obese
- 40 and over is considered extremely obese
The problem is, BMI is not a perfect indicator of health. For starters, it doesn’t take muscle mass into account. That means that a person who is physically fit and quite muscular may be considered “overweight” or “obese” because muscle tends to weigh more than body fat.
BMI is also unable to measure the amount of fat located around the belly. Having a lot of belly fat indicates a larger waistline and may be particularly dangerous for your heart (more on this below).
It’s also important to note that BMI is not a good predictor of health risks across racial groups. This means that two people with different racial backgrounds may have different risks at comparable BMI levels.
For example, Asian and Asian American people may have more health risks at lower BMIs than non-Asian people. Research has shown that the chance of developing diabetes increases at lower BMI values in South Asian and Chinese people, compared to Black and white people. HCPs need to take this information into account when deciding what a particular patient’s BMI may mean for them.
Why waist measures matter
Even though BMI remains the go-to measurement of body health, research suggests that paying attention to waist measurements may be more accurate. Specifically, research into WHR points to why pear-shaped people tend to live longer than apple-shaped people, even if their overall weights and heights are comparable.
A 2019 review published in Canadian Family Physician looked at the question of “central obesity” (or large deposits of fat around the waist) in people whose BMIs were considered to be in the healthy range. Researchers found that central obesity (commonly described as having an apple shape) was more closely related to a risk for illness and death than simple weight or BMI measures.
Another study, published in 2019 in the European Heart Journal, looked at postmenopausal women in the United States with BMI measurements considered healthy. Researchers found that those who had more upper-body or “trunk” fat and lower amounts of leg fat had three times the risk of developing heart disease than those who had no upper or lower body fat, or those with just leg fat. A large review of research published in 2020 in The BMJ, meanwhile, found that central obesity was significantly linked to a higher risk of premature death.
Meanwhile, a consensus statement published in 2020 in Nature Reviews Endocrinology recommended that HPCs treat waist circumference as an essential vital sign. The authors advised that it should be measured and taken into account, just like weight and blood pressure.
What’s the problem with belly fat?
Researchers aren’t exactly sure what makes certain types of fat dangerous, but it likely has to do with where—and how deep—it’s located in your body.
If you’re considered to be pear-shaped, your fat tends to be located mostly in your lower half. It also tends to be mostly subcutaneous fat, meaning it sits right under the skin.
People who are apple-shaped, on the other hand, have more fat in their abdomen. That fat, called visceral fat, is deeper and collects around the organs. Researchers think visceral fat may affect body systems in a more dangerous way than subcutaneous fat. For example, visceral fat may disrupt hormones and produce chemicals that lead to inflammation, a major contributor to heart disease and cancer.
What you can do
First, it’s important to understand that targeted fat loss, sometimes called "spot reduction," does not work. There’s no way to specifically eliminate belly fat by exercising muscles around the belly. So, while sit-ups and crunches may help you develop some of your abdominal and core muscles, they alone won’t burn off belly fat.
Instead, the best way to lose fat all over is to maintain a healthy lifestyle. This includes:
Exercise: To burn calories, get at least 30 minutes a day of aerobic exercise that gets your blood pumping and your heart rate up. Think brisk walking, jogging, biking, hiking, playing sports, or doing resistance training with weights or elastic bands.
Diet: Eat a healthy diet focused on fruits and vegetables, whole grains, lean proteins, and healthy fats from sources like vegetables and seafood. As much as possible, reduce your intake of processed foods and foods with added sugars, like sweetened soda, candy, and cookies. Drink alcohol in moderation, if at all. That means no more than two drinks per day for men and one drink per day for women. Some research suggests a link between drinking alcohol and obesity.
Sleep: Not getting enough quality sleep may raise your risk of putting on more visceral fat. Aim for seven to nine hours of sleep per night. Some research suggests that having sleep apnea increases the chances that someone who is overweight will gain more weight. (Sleep apnea is a disorder that involves repeated wakeups during sleep.)
Stress reduction: When you’re stressed, your body releases more of a hormone called cortisol, which may increase the storage of visceral fat. There are many ways to reduce stress, from exercising, to practicing meditation, to using deep-breathing methods, to journaling or talking to friends or a therapist.
The good news is that when you put together these healthy habits (with an emphasis on exercise), visceral fat reduces more easily than subcutaneous fat. Just a few months of maintaining a healthy lifestyle can improve your body weight and size—and yield results that could benefit you for a lifetime.
