A new study has found that the obesity epidemic in the United States may be far worse than previously thought. 

Scientists from the latest research said that the "gold standard" formula or Body Mass Index, a calculation that combines a person’s height and weight to give a score used to distinguish between healthy and unhealthy weight, could actually be incorrectly categorizing dangerously overweight people as having healthy weight. 

While the U.S. Centers for Disease Control says that at least one in three Americans is obese, the latest findings using X-ray scans that directly measured body fat, suggest that up to 39 percent of people who were not currently considered to be obese actually were. 

The investigators said "we may be much further behind than we thought" in fighting obesity.

"The BMI is an insensitive measure of obesity, prone to under-diagnosis," said co-author Dr. Eric Braverman in a statement released on Monday, "while direct fat measurements are superior because they show distribution of body fat."

Investigators had analyzed dual-energy X-ray absorptiometry, or DXA, scans for more than 9,000 patients in New York from 1998 to 2009, which measured body fat as well as muscle mass and bone density.

The findings show that based on BMI measurement alone, about 26 percent of the participants in the study were classified as obese, while more than double, at 64 percent were considered obese based on DXA results.

"These estimates are fundamental to U.S. policy addressing the epidemic of obesity and are central to designing interventions aimed at curbing its growth," the authors wrote, "yet the [current policies] may be flawed because they are based on the BMI."

Currently, a BMI score of 25 to 29.9 is considered overweight and a BMI of 30 or above is considered obese, and researchers suggest that a more appropriate cut off point for obesity should be a BMI of 24 for women and 28 for men. 

Investigators had also found that levels of a hormone protein called leptin strongly correlated to body fat, and they recommend that in the absences of DXA, measurements of leptin levels may be used in conjunction with MBI to provide a more accurate measure of healthy or unhealthy weight.

The study was published Apr. 2 in the journal PLoS ONE.