Study Shows EOSS Tool Predicts Health Risks of Obese Patients
By Brenda Goodman
WebMD Health News
Reviewed by Laura J. Martin, MD
Aug. 15, 2011 -- Researchers are testing a new tool that helps doctors figure out which overweight and obese patients are most in need of medical treatment and which are likely to remain healthy, even at very large sizes.
The tool, called the Edmonton Obesity Staging System (EOSS), was developed by researchers in Canada, a country where people who need weight loss surgery can linger for years on waiting lists.
"When you have a waiting list, you try to think about how you prioritize people on that waiting list," says study researcher Arya M. Sharma, MD, PhD, professor and chairman of obesity research and management at the University of Alberta, in Edmonton, Canada, "Who do you see first?"
"So we thought, maybe take the heaviest patients first because they might be the people who are sickest," Sharma tells WebMD. "But when we looked at that closely, we found that that isn't always true."
Doctors call this the obesity paradox.
In a study published in 2007 in The Journal of the American Medical Association, CDC researchers found that overweight people had a decreased risk of dying compared to people who were either underweight or very obese.
"We found that in terms of excess deaths, that is, deaths above what you would predict if the person had been normal weight, in the overweight category, there were fewer deaths than you would have predicted, that is, overweight was some way associated with lower mortality," says Katherine M. Flegal, PhD, senior research scientist at the National Center for Health Statistics.
"There's a fairly large literature now suggesting that in a lot of situations, if you have a medical condition, your survival is better at a slightly higher weight," she says.
"Body weight is not the strongest risk factor for a lot of conditions," Flegal says. "It's just one of many risk factors."
Other experts agree.
Joel Zonszein, MD, an endocrinologist and professor of clinical medicine at the Albert Einstein College of Medicine in New York, says that body mass index (BMI), a measure that takes into account both a person's height and weight, alone doesn't say very much about a person's overall health.
"BMI is simple, but it doesn't tell the whole story," he says.
Staging Obesity-Related Health Risks
To address these problems, Sharma and his team developed a scale, from 0 to 4, that stages overweight and obese people in much the same way that oncologists stage cancer.
In both systems, stage 1 or 2 isn't as life threatening as stage 3 or 4.
The stage largely depends on how many other health problems are present with the extra weight.
For example, a person at stage 1 on the EOSS might be obese with borderline high blood pressure or prediabetes. They could also have occasional aches and pains, fatigue, or they might get short of breath after mild physical activity, like climbing a flight of stairs.
To test the tool, the researchers applied it to nearly 8,000 Americans who took part in the government's ongoing National Health and Nutrition Examination Surveys (NHANES) from 1988 to 2004.
Each person who met the definition of being overweight, meaning they had a height and weight that gave them a BMI over 25, was also given an EOSS score.
The stages were assigned based on whether they also had diabetes, high blood pressure, high cholesterol, osteoarthritis, liver or kidney disease, trouble moving around, metabolic syndrome, and a large waist and high triglycerides.
A person's size, the study found, wasn't a very good predictor of how healthy they were.
More than three-quarters of the overweight and obese people in the study received scores of 1 or 2 on the EOSS scale.
And when researchers cross-referenced their work against death records, they found that BMI wasn't a reliable predictor of a person's death risk, but their EOSS score was.
About 90% of people who were classified as stage 1 when they started the study, for example, were still alive more than 17 years later, compared to roughly 55% of people who were at EOSS stage 3.
Compared to people with an EOSS score of 0 or 1, meaning they had few health problems, those at stage 2 had a roughly 60% increased risk of death, and those at stage 3 had nearly three times the risk of dying over the next 20 years.
Doctors say the study, which is published in the Canadian Medical Association Journal, doesn't mean that people shouldn't worry about weight loss.
"The likelihood of having an obesity-related health problem," such as heart disease or diabetes, "increases with your BMI," Sharma says.
But he says size clearly isn't the only determinant of health. "Even at the highest category of weight [having a BMI over 40] there are still about 20% of people who have no problems."
Though the tool needs further testing, researchers hope it may one day help patients who are healthy, and their doctors, make peace with their extra pounds, whatever their particular number may be.
"On the other hand, if someone has a BMI of 28 or 29 and their EOSS is 2 or 3, then you start to say, well this person has a lot of accumulated illnesses stemming from their weight," says study researcher Raj S. Padwal, MD, associate professor in the department of medicine at the University of Alberta. "You'd say, 'we really need to get on this.'"