The effect of lifestyle habits on type 2 diabetes risk is so large that it renders genetic susceptibility insignificant, according to a study led by researchers from the University of Cambridge and published in the journal PLOS Medicine.
The study was funded primarily by the European Commission.
The findings imply that generalized lifestyle interventions are still the most effective way to prevent diabetes, regardless of an individual’s genetic profile.
“One of the most effective ways to reduce the impact of type 2 diabetes is to stop people developing the condition in the first place,” researcher David Lomas said, “and this large international study reinforces the idea that broad promotion of a healthy diet and lifestyle is the way to go.”
Genetic tests not supported
Type 2 diabetes, which occurs when the body loses its sensitivity to the blood-sugar-lowering hormone insulin, now affects more than 380 million people globally. As with many chronic diseases, researchers believe that it originates from an interaction between underlying genetic risk and various lifestyle factors, including diet and exercise.
In recent years, scientists have identified numerous gene variants associated with risk for the disease, and screening for such variants has become popular. One New Delhi, India-based screening company reports that it gets approximately 3,000 customers a month from 150 separate locations across India.
But the new study casts doubt on the usefulness of such tests.
“There is no good evidence that the knowledge of these variants currently helps predict risk (of diabetes) nor in informing what action people should take,” lead researcher Nicholas Wareham said. “The currently known genetic variants don’t help personalise prevention.”
In contrast, generalized lifestyle interventions have been proven to reduce the chances of high-risk individuals developing the disease by 50 percent.
“I think such tests at this point in time are a waste of money,” said Anoop Misra, chairman of the Fortis Centre for Diabetes Obesity and Cholesterol in New Delhi. “Diabetes can be simply predicted by presence of obesity, family history, and age.”
Obesity is greatest predictor
In the new study, the researchers used data from the European Prospective Investigation into Cancer and Nutrition (EPIC) study to calculate a diabetes genetic risk score for 12,403 middle-aged type 2 diabetes patients and 16,154 people without the disease. These scores were based on the presence or absence of 49 separate gene variants that have been linked to the disease. The researchers then compared the effect of genetic risk with that of lifestyle-related risk (such as poor diet or exercise habits).
The researchers found that, among people of normal weight, only 0.25 percent of those with the lowest genetic risk and 0.89 percent of those with the highest genetic risk went on to develop type 2 diabetes. In contrast, 4.22 percent of obese people with the lowest genetic risk developed the disease, and 7.99 percent of obese people with the highest genetic risk.
This shows that obesity far outweighs genetics as a predictor of diabetes risk. It also suggests that there is no need to specifically target some people for diabetes prevention based on their individual genetic profiles — interventions should be generalized, or simply targeted at people with unhealthy lifestyles.
“We need effective strategies in place if we are going to stem the rapid rise in the number of cases of type 2 diabetes and the burden this places on our health systems,” Wareham said. “Our research suggests that focusing on tackling the lifestyle factors that lead to obesity at a population level will have a much greater impact than tailoring prevention strategies according to an individual’s genetic risk.”
“The public health message is that everyone should minimise the risk of diabetes through physical activity and a healthy diet,” he said.