New data released this month from the Centers for Disease Control (CDC) shows that the average American waistline has increased 1.2 inches in the last 12 years, despite the fact that our national obesity level seems to have plateaued (at least for now).Americans are not getting fatter, but their waistlines are.The CDC looked at the average waist circumference from 1999 to 2012, using data from 32,816 men and nonpregnant women in the National Health and Nutrition Examination Survey (NHANES), a gigantic population survey used to determine many of our public health statistics. Prior analyses of the NHANES population show that the prevalence of obesity calculated from body mass index (BMI) did not change significantly between the 2003-2004 and the 2011-2012 surveys. While we all patted ourselves on the back and thought the obesity epidemic was on the mend, a different type of obesity was taking shape.

Abdominal obesity prevalence in women has leapt nearly 10 percentage points since the millennium, to 64.7 percent.

And that shape is round.Our overall weight may not be changing, but the places we are gaining weight are—more is heading to our waistlines than ever before. From the health perspective, the waistline is the worst place to gain weight. Waist circumference has been linked to cardiovascular disease, insulin resistance syndrome and increased risks of breast, colorectal and renal cancer.The researchers listed a few surprising factors as potential explanations, including sleep deprivation, endocrine disruptors, and the prevalence of certain medications.This isn’t the first time we’ve seen increases in waist circumference outpace increases in BMI. A study published in Obesity showed small but consistent increases in waist circumference in the U.S. population from the 1960s to 2007, even when measured at any fixed BMI level. Scientists say it’s plausible that endocrine disruptors, along with other contaminants persistently found in the environment, lead to increases in stomach fat and changes to our body’s internal distribution of fat.Women are faring worse than men.Abdominal obesity is defined as a waist circumference greater than 40.2 inches in men and greater than 34.6 inches in women. The waistline of the average American grew from 37.6 inches in 1999-2000 to 38.8 inches in 2011-2012. Women outpaced men with an average increase of 1.5 inches, compared to the male average of 0.8 inches. But it’s the data on the prevalence of so-called “abdominal obesity” where women really stand out. Nationally, we’ve jumped from below to above the 50 percent mark for abdominal obesity. The rate among men has stayed below this average, increasing 6.4 points to 43.5 percent. Abdominal obesity in women, meanwhile, has leapt nearly 10 percentage points since the millennium, to 64.7 percent. That number is even higher—70 percent—for black and Mexican American women.Where do we go from here? To the measuring tape. Though weight and BMI are useful measurements to get a baseline sense of body health, they are imperfect metrics that don’t take into account the distribution of fat (among other things). If you’re staying at the same weight or BMI, but putting on inches around the middle, it may be an indication of a dangerous accumulation of visceral fat surrounding your inner organs. This new report is a scary but important reminder to pay attention not just to the numbers on the scale, but also to our overall body shape as it relates to health and longevity.