Healthy obesity often becomes unhealthy over time, Many people who are overweight but seem otherwise healthy will eventually have an unhealthy increase in blood pressure and other metabolic risk factors over a 20-year period, a new study suggests.
Most "healthy obesity" becomes unhealthy obesity over time, the authors write.
“These results were not overly surprising, as we already know that healthy obese adults have a greater risk for developing type 2 diabetes and cardiovascular disease than healthy normal-weight adults,” said lead author Joshua A. Bell of University College London, in an email to Reuters Health.
In earlier, shorter studies, about a third of healthy obese adults progressed to unhealthy obesity, Bell said. His new study, which tracked people for at least 10 years longer than those earlier studies did, “indicates that this tendency gets stronger with time, with about half making this transition after 20 years,” he said.
Healthy obesity is often just a phase, he added.
Bell’s team used data from an ongoing study of more than 2,500 British civil servants, with health metrics collected every five years.
In 1992, 66 participants were classified as "healthy obese." Although extremely overweight, they had no more than one of the following metabolic risk factors: low levels of “good” HDL cholesterol, high blood pressure or use of blood pressure medication, high fasting blood sugar levels, insulin resistance, or use of medication for diabetes.
After 20 years, 34 of the “healthy obese” – just over half of the original number – had added more of the metabolic risk factors and had become "unhealthy obese," the researchers estimated.
Ten percent of the original healthy obese group had lost weight and were “healthy nonobese” by the 20-year mark, while the remaining 38 percent stayed in the healthy obese group for the duration, the researchers reported in the Journal of the American College of Cardiology.
Overall, those who started as healthy obese were almost eight times more likely to have become unhealthy obese than those who started at a healthy weight.
Other evidence suggests that over the long term, healthy obesity doesn’t exist and that obese people, regardless of their metabolic health, will probably have poor health outcomes, Dr. Sarah Appleton of the University of Adelaide, The Queen Elizabeth Hospital Campus in Woodville, Australia, told Reuters Health by email.
Appleton was not involved in the new study.
“When carrying excess fat, the tissues of the body become resistant to the hormone insulin, which leads to poor control of sugars and fats in the blood,” Bell said. “It matters where fat is located in the body, with visceral fat located abdominally and around organs being particularly harmful, while subcutaneous fat located more peripherally is less harmful.”
“Healthy obese adults may have a more favorable fat distribution, but the number of healthy obese adults who can maintain an optimal balance of fat stores in the long-term is not high,” he said.
Healthy obesity, which does not have a universal definition in the medical community, may be a transient condition, said Dr. Ravi Retnakaran, an endocrinologist and clinician-scientist at Mount Sinai Hospital in Toronto.
“In the debate over healthy obesity and whether it exists, most of the time healthy obesity has been defined on the basis of a person’s metabolic status at one point in time,” Retnakaran, who was not part of the new study, told Reuters Health by phone.
“The literature really is lacking in these types of studies with repeated assessment,” he said. “You may not be completely out of the woods if you’re classified as healthy obese.”
“Our results stress the need to take a long-term view of healthy obesity,” Bell said. He added, “Healthy obesity is still a high risk state – the harmful effects may just be delayed.”
