White House doctor Ronny Jackson said he did not perform a key measurement of Trump's physical fitness, despite his borderline-obese weight of 239 pounds.

Physicians are increasingly turning to waist circumference as an important indicator of overall health.

High amounts of abdominal fat have been linked with an increased risk of heart disease and diabetes.

At a press conference on Tuesday, White House doctor Ronny Jackson said he did not measure a key indicator of Trump's physical fitness: his waist circumference.

The President weighed in at 239 pounds, which puts him on the border of what's considered obese for his height. Jackson nonetheless described the president as in "excellent health," and said he did not feel a need to measure Trump's waist.

However, physicians are increasingly recognizing waist size as a key measure of health.

Several studies have documented a link between high amounts of abdominal fat and an increased risk of heart disease and diabetes. In a large 2012 study, researchers looked at data from more than 340,000 Europeans and found that people who were overweight and had large waists — 34.5 inches or more for women and 40 inches or more for men — had nearly the same risk of developing Type 2 diabetes as people who were clinically obese.

One of the most perilous pitfalls of BMI — another measure that Jackson said he did not calculate for Trump — is that it doesn't account for fat carried around a person's abdomen. All it measures is the ratio of height and weight, which is why some lean people with large amounts of muscle can have a BMI that would qualify as "overweight."

Scientists still aren't sure why excess fat around our middle is connected to negative health outcomes, but they think it has to do with how fat inside the body, known as visceral fat, may interfere with the normal functioning of our internal organs.

Public-health experts have known for years that BMI isn't a perfect tool for measuring physical fitness and that an improved metric would incorporate waist circumference.

"For health, the issue is not how much you weigh, but how much abdominal fat you have," a 2005 Harvard Medical School blog post said.

Although Jackson did not account for Trump's waist measurement in his analysis, he did mention plans to help improve the president's diet and institute some kind of exercise program.