BMI doesn't touch on cardiovascular fitness or body composition, Shape reported.
Researchers from the University of Copenhagen in Denmark analyzed the heights, weights, and mortality rates of more than 100,000 people.
Relate: Obesity in America
Obesity problem in America
New study: The healthiest BMI is actually 'overweight'
An overweight man wears a shirt patterned after the American flag during a visit to the World Trade Center, Thursday, May 8, 2014 in New York. (AP Photo/Mark Lennihan)
In this Nov. 16, 2012 photograph, Stonebridge Elementary School children are offered a nutritious menu that includes burgers and tater tots that were prepared in a combi-oven, a cross between a steamer and an oven, in the school's kitchen in Brandon, Miss. The device can make frozen french fries and tater tots crisp without all that waistline-expanding oil. (AP Photo/Rogelio V. Solis)
In this photo taken Jan. 2, 2016, baskets of organic spinach and other leafy greens are displayed for sale at a farmers market in Falls Church, Va. The Obama administration's latest dietary guidelines, released Thursday, Jan. 7, 2016, to help Americans reduce their likelihood of disease and obesity through a more healthful diet. The main message hasn't changed much over time: Eat your fruits and vegetables, whole grains and seafood, and keep sugar, fats and salt in moderation. (AP Photo/J. Scott Applewhite)
In this March 14, 2014 picture, students take part in an early morning running program at an elementary school in Chula Vista, Calif. Amid alarming national statistics showing an epidemic in childhood obesity, hundreds of thousands of students across the country are being weighed and measured. The Chula Vista Elementary School District is being touted as a model for its methods that have resulted in motivating the community to take action. (AP Photo/Gregory Bull)
In this June 17, 2013 photo, two women cross the street in Barre, Vt. In its biggest policy change on weight and health to date, the American Medical Association has recognized obesity as a disease. (AP Photo/Toby Talbot)
FILE - This Thursday, May 31, 2012 file photo shows a display of various size soft drink cups next to stacks of sugar cubes at a news conference at New York's City Hall. New research greatly strengthens the case against soda and other sugary drinks as culprits in the obesity epidemic. Two major experiments found that children and teens gained less weight when they regularly drank calorie-free beverages instead of sugary ones. A third study gives the first clear evidence that consuming sugary drinks interacts with genes that affect weight. Scientists say the results add weight to the push for taxes, size limits and other policies to curb consumption. (AP Photo/Richard Drew, File)
SAN FRANCISCO, CA - JUNE 10: Sugar is listed in the ingredients of a bottle of soda that is displayed in a cooler of a food truck on June 10, 2015 in San Francisco, California. The San Francisco board of supervisors has approved an ordinance that would require warning labels to be placed on advertisements for soda and sugary drinks to alert consumers of the risk of obesity, diabetes and tooth decay. The ordinance would also ban advertising of sugary drinks on city-owned property. If San Francisco mayor Ed Lee approves the measure, the law would be the first of its kind in the nation. (Photo by Justin Sullivan/Getty Images)
Michael Saucedo, age 9, showed his plate of chicken strips, chocolate milk, fruit cup, oranges and wheat bread, at Russell Cave Elementary School in Lexington, Ky., Wednesday, Jan. 13, 2010. The chicken strips are fried before arriving at the school, then are reheated using a steam and convection oven. Debate in Washington over a controversial school lunch waiver has spread into the Bluegrass State, where proponents say the innocuous proposal helps rural schools, and which critics argue threatens years of work combating one of the nationÃs largest childhood obesity rates. The House of Representatives is expected to vote this week on an appropriations bill that includes the waiver provision. (Pablo Alcala/Lexington Herald-Leader/MCT via Getty Images)
A heavy set man rests on a bench in Jackson, Miss., Thursday, Sept. 4, 2014. A report released Thursday by Trust for America's Health and the Robert Wood Johnson Foundation found adult obesity rates at 35.1 percent in both Mississippi and West Virginia have placed them with the highest rates of adult obesity in the nation. It marks the first time that a state has surpassed 35 percent. The study showed an alarming 20 states had obesity rates of 30 percent or higher in 2013, up from 12 states in 2010. Nine of the 10 fattest states are in the South. (AP Photo/Rogelio V. Solis)
Steve Cahillane, president and CEO of Coca-Cola Refreshments, Inc., speaks during an interview with the Associated Press Thursday, June 7, 2012, while attending the Clinton Global Initiative America gathering in Chicago. Cahillane said that New York Mayor Michael Bloomberg's proposal to ban the sale of large sodas and other sugary drinks unfairly singles out an industry. He says the measure is overly simplistic and would do nothing to address the complex problems of obesity and other health issues. (AP Photo/M. Spencer Green)
FILE - In this June 26, 2012 file photo, two women speak to each other in New York. A national telephone survey found 13 states with very high rates of obesity. A national telephone survey found 13 states with very high rates of obesity in 2012. But overall, the proportion of Americans deemed obese has been about the same for years now. Results were made available by the Centers for Disease Control and Prevention. "A plateau is better than rising numbers. But it's discouraging because we're plateauing at a very high number," said Kelly Brownell, a Duke University public policy expert who specializes in obesity. (AP Photo/Mark Lennihan)
People walk on the street, Thursday, July 7, 2011, in Montpelier, Vt. National statistics show that Vermont is dropping from its perch near the top of national rankings of the least obese states. In 1995, 13.4 percent of Vermonters were considered obese. Now the figure is 23.5. (AP Photo/Toby Talbot)
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They found obesity isn't as dangerous as it used to be. In fact, they found the overall mortality rate for obese people (BMI of 30 or greater) is no longer higher than it is for people of normal weight (BMI between 18.5 and 24.9).