The scientists examined electronic health records from 1995 to 2015 in the
Health Improvement Network – a large UK general practice database.
They found records for 3.5 million people who were free of coronary heart disease at the starting point of the study and divided them into groups according to their BMI and whether they had diabetes, high blood pressure [hypertension], and abnormal blood fats [hyperlipidemia], which are all classed as metabolic abnormalities. Anyone who had none of those was classed as “metabolically healthy obese”.
The study found that those obese individuals who appeared healthy
in fact had a 50% higher risk of coronary heart disease than people who were of normal weight. They had a 7% increased risk of cerebrovascular disease – problems affecting the blood supply to the brain – which can cause a stroke, and double the risk of heart failure.
Dr Rishi Caleyachetty, who led the study, said it was true that weightlifters could be healthy and yet have a BMI that suggested they were obese. “I understand that argument. BMI is crude … but it is the only measure we have in the clinic to get a proxy for body fat. It is not realistic [to use anything else] in a GP setting or in the normal hospital clinic. We have to rely on BMI measurements, however crude they may be,” he said.
While BMI results for particular individuals could be misleading, the study showed that on a population level, the idea that large numbers of people can be obese and yet metabolically healthy and at no risk of heart disease was wrong.