Is obesity always unhealthy? Some studies have tried to answer that question by looking at those who are “fat but fit” — obese but still physically active. A new study takes a different tack: If people are obese but without other cardiovascular risk factors, do they still have a higher rate of things like heart attack and stroke?
The answer, in one of the biggest studies yet to weigh in on the question, is yes.
Using an electronic health record database of 3.5 million people, researchers at the University of Birmingham in England separated people into categories based on their body mass index (BMI) and whether they had type 2 diabetes, hypertension, high cholesterol, or more than one of those illnesses. People were categorized as “obese” if they had a BMI over 30.
Over the course of a follow-up period — on average, 5 1/2 years — researchers watched to see if these people would experience one of four categories of diseases that affect the heart and vascular system.
After controlling for a variety of factors, including whether someone ever smoked cigarettes or was taking hormones or contraceptives, the researchers found that people who were obese had a nearly 50 percent increased risk of coronary heart disease and almost double the risk of heart failure as someone who fell into a “normal weight” BMI category. Importantly, this held true even if the obese group was limited to those without any other contributing health conditions.
“It is important to remember though that fat is not just an energy store, but an active organ like the heart,” said G. Neil Thomas, an author of the paper and a researcher at the University of Birmingham’s Institute of Applied Health Research. “It acts to help control food intake and factors like inflammation that have been shown to cause heart disease. It should therefore be no surprise that if you have more of it there will be consequences.”
The results were published in the Journal of the American Academy of Cardiology on Monday.
“This paper is excellent,” said Mercedes Carnethon, a professor of preventive medicine at Northwestern University who was not involved in the research. “Obesity has become so common that we’re trying to find ways to distinguish among those who are obese and at higher risk for disease compared with those who may be obese but it may be a benign condition.”
Health and weight
The study does have a few limitations. BMI can be an imperfect measure, and researchers didn’t have access to any data about diet or physical activity. It also only surveyed people in the United Kingdom, though it did cover about 6 percent of the population; previous studies had validated the use of that database for other epidemiological studies.
Since the 1960s, there has been a growing “fat acceptance” movement, which has drawn attention to discrimination and stigma faced by people who are overweight or obese. Some have also promoted the idea that people who are obese but otherwise healthy and physically active are just that — healthy. Media attention around that idea first drew Thomas to the field; Carnethon herself has published data suggesting that overweight and obese adults have lower mortality rates in some cases.
Thomas and Carnethon agreed that discrimination against people who are overweight is “appalling” and “terrible.”
“There is a group who really promotes fat acceptance and positive self-esteem and loving yourself no matter what your size. I think that that is an important perspective to have,” Carnethon said. “But I also think that these data suggest that these individuals are going to have more cardiovascular events.”
“While I think stigmatization of overweight and obese [people] is a terrible thing, I think that obesity is a disease that needs to be treated seriously as a disease.”
To Thomas, the data are pretty clear. “The main takeaway message of the study is that ‘metabolically healthy’ obesity, on a population level, simply does not exist.”