In a comprehensive new study, a team of 36 health experts have concluded that being extremely obese is more likely to kill you than being a healthy weight. The paper was 14 pages long and was not published in the Onion.

Obvious as it seems, the research was published in PLOS Medicine and isn’t as inane as it sounds. (Especially relative to this paper in Radiology that suggested swallowing multiple magnets is dangerous.) In fact, sometimes it’s useful to demonstrate well-known phenomenon over and over (ahem, climate change). Ultimately, they revealed that the fattest among us have mortality rates more than twice as high as normal-weight people.

But there’s another good reason for their investigation: Americans have never been fatter. In the early 1960s, when the CDC surveyed the nation’s weight, fewer than one percent were considered “extremely obese.” But by 2010, the population of extremely obese Americans was closing in on seven percent. (For those who don't know, the categories overweight, obese, and extremely obese are based on a person’s body mass index, or BMI. It's a function of an individual’s weight and height. For example, a 6-foot-tall person who weighs 294 pounds or more is considered extremely obese.)

The authors of the new study, led by Cari M. Kitahara of the National Cancer Institute, say extreme obesity, which they refer to as class III obesity, hasn't been studied very much because until recently it's been pretty rare. Research on the toll of the problem has been small-scale. “The few studies that have specifically evaluated mortality rates associated with class III obesity generally had limited sample sizes,” they said.

So for this study, they examined the cases of 9,564 non-smoking adults who were extremely obese and studied their mortality rates over three decades, noting the number of deaths per 100,000 per year. They discovered their mortality rate was 856 for men and 663 for women. People with normal weight died at a much lower rate: 346.7 and 280.5 for men and women, respectively.

What does that mean? Being very fat kills as effectively as smoking does. In fact, the obese study participants died six to 14 years sooner than their peers from diseases that were most often heart disease, cancer, or diabetes.

Clearly the personal cost of obesity is enormous. Nearly one in 17 U.S. adults — people’s fathers, mothers, siblings, and friends — are in danger of dying because of their weight. But there’s a public cost, too, highlighted by a recent study showing that each obese child costs $19,000 more over his or her lifetime than a healthy weight child. With obesity rates showing no sign of abating, the PLOS Medicine editors wrote, “these findings highlight the need to develop more effective interventions.”

Source: Kitahara CM, Flint AJ, Berrington de Gonzalez A et al. Association between Class III Obesity (BMI of 40-59 kg/m2) and Mortality: A Pooled Analysis of 20 Prospective Studies. PLOS Medicine. 2014.