Researchers at Loughborough University have found a link between the length of time someone has spent above the obesity threshold – based on the BMI scale – and levels of blood pressure, cholesterol and HbA1c.
Glycated hemoglobin (HbA1c) is caused when sugar attaches itself to red blood cells.
High levels of HbA1c are an indicator of developing diabetes and related complications – it is also linked to elevated risk factors related to heart disease and stroke.
In a study of more than 20,000 people, one key finding showed that even after accounting for severity of obesity, the longer someone spends obese the worse the level of blood sugar (HbA1c).
This is not the same for the other risk factors.
The study showed that adults with less than five years of obesity had a 5% higher HbA1c compared to adults with no years of obesity.
For adults with 20-30 years of obesity, HbA1c was 12% higher.
Dr Tom Norris, Senior Research Associate in Epidemiology and Biostatistics, lead author of the paper, said: “The motivation for the study was to try and understand why some people with obesity have a greater risk for diseases that affect the circulatory and endocrine systems than other people who also have obesity.
“We tested the idea that the length of time a person has obesity is responsible.
“We found that longer time with obesity resulted in worse blood pressure, cholesterol, and HbA1c.
“Importantly though, greater obesity duration was still associated with worse HbA1c even after accounting for obesity severity. This was not true for blood pressure and cholesterol.”
The study used data from three British birth cohort studies (20,746 participants) that collected information on body mass index from age 10 to 40 as well as cardiometabolic disease risk factors—blood pressure, cholesterol and HbA1c measurements.
Other measures of cardiometabolic disease risk (systolic and diastolic blood pressure, high-density lipoprotein cholesterol) were also associated with obesity duration, though these associations were largely attenuated when adjusting for obesity severity.
Senior author of the paper Dr Will Johnson, Senior Lecturer in Epidemiology and Population Health, added: “The results suggest that developing obesity earlier in life may be related to worse HbA1c even if obesity severity is low.
“For example, in an individual whose body mass index is only just above the obesity threshold.
“This is important because the UK is experiencing an obesity epidemic characterised by children becoming obese at younger ages.”
The work was funded by an MRC New Investigator Research Grant and was carried out in partnership with University College London and the University of Cambridge.
The paper, Duration of obesity exposure between ages 10-40 years and its relationship with cardiometabolic disease risk factors: a cohort study, has been published in journal PLOS Medicine.