Researchers have found that obesity increases the risk of developing type 2 diabetes by at least six times, regardless of genetic predisposition to the disease.
"The results suggest that type 2 diabetes prevention by weight management and a healthy lifestyle is critical across all genetic risk groups," said study researchers from the University of Copenhagen in Denmark.Using data from a case-cohort study nested within the Diet, Cancer and Health cohort in Denmark, the research team examined the joint association of obesity, genetic predisposition, and unfavourable lifestyle with incident type 2 diabetes (T2D).
The study, published in the journal Diabetologia, included samples of 4,729 individuals who developed type 2 diabetes during a median 14.7 years of follow-up, and a randomly selected cohort sample of 5,402 individuals (the control group).
Overall, 21.8 per cent of all participants were classified as obese, 43.0 per cent as overweight and 35.2 per cent as having normal weight; and 40.0 per cent of the participants had a favourable lifestyle, 34.6 per cent had an intermediate lifestyle and 25.4 per cent had an unfavourable lifestyle.
Genetic predisposition was quantified using a genetic risk score (GRS) comprising 193 known types 2 diabetes-associated genetic variants and divided into five risk groups of 20 per cent each from lowest to highest genetic risk.
Statistical modelling was used to calculate the individual and combined associations of the GRS, obesity and lifestyle score with developing T2D.
Compared with people of normal weight, those with obesity were almost six times more likely to develop T2D, while people who were overweight had a 2.4 times increased risk.For genetic risk, those with the highest GRS were twice as likely to develop T2D as those with the lowest, while those with the unhealthiest lifestyle were 18 per cent more likely to develop T2D than those with the healthiest.
According to the study, individuals who ranked high for all three risk factors, with obesity, high GRS and unfavourable lifestyle, had 14.5 times increased risk of developing T2D, compared with individuals who had a normal body weight, low GRS and favourable lifestyle.
Notably, even among individuals with a low GRS and favourable lifestyle, obesity was associated with 8.4 times increased risk of T2D compared with normal-weight individuals in the same genetic and lifestyle risk group, the researchers said.
"We found that the effect of obesity on type 2 diabetes risk is dominant over other risk factors, highlighting the importance of weight management in type 2 diabetes prevention, the authors wrote.