Their new study found that obesity increased the risk of type 2 diabetes by at least six times, no matter what a person's genetic risk was.
"Obesity and unfavourable lifestyle are associated with increased risk of type 2 diabetes irrespective of genetic risk," said study author Hermina Jakupovic. She's a doctoral fellow in biomedicine at the University of Copenhagen in Denmark.
These findings suggest that no matter what your family history might be, maintaining a healthy weight is a key to keeping type 2 diabetes at bay.
Lifestyle and genetic risk
"Weight management by healthy lifestyle should be recommended as a prevention strategy, regardless of genetic predisposition," Jakupovic said.
Her team used data from a diet, cancer and health study in Denmark. It included people whose health was tracked for a median of 15 years (meaning half were followed longer, half for less time). More than 4 700 adults developed type 2 diabetes during the tracking.
Among all these study participants, the average age was 56, and slightly more than half were men. Nearly 22% were obese, while 43% were overweight. Just over 35% were normal weight, the researchers reported.
Lifestyle was assessed using a score based on physical activity, diet, alcohol consumption and smoking. About 40% had a favourable lifestyle score and just over 25% had what the researchers called an unfavourable lifestyle.
Genetic risk was measured with blood tests that looked for 193 gene variants known to be associated with type 2 diabetes. The genetic results were grouped from lowest risk to the highest (having the most genetic variants). People with the most genetic variants were twice as likely to develop type 2 diabetes as those with the least, the findings showed.
Compared to people whose weight was normal, those who were overweight had a 2.4 times higher risk of developing type 2 diabetes during the study. For those who were obese, the risk was six times higher.
Important to prevent obesity
When researchers looked only at lifestyle, people with the least healthy habits – the unfavourable group – were 18% more likely to get type 2 diabetes than those with the healthiest habits.
People with the unhealthiest lifestyle, a high genetic risk and obesity had more than 14 times the risk of type 2 diabetes.
Dr Robert Eckel, president of medicine and science for the American Diabetes Association, said the findings weren't a surprise. Obesity is a well-known risk factor for type 2 diabetes, he said.
"Genetic variants only explain about 10% to 15% of type 2 diabetes risk, although I think we may not completely understand all of the type 2 genes," he noted.
Eckel said the findings are yet more evidence highlighting how important it is "to prevent obesity, to begin with. Everyone needs to control their energy balance." That means you can't eat more calories than you use up with activity.
Keeping the weight off
Physical activity is an important component of maintaining a healthy weight, too, he added.
Previous studies have shown that losing even a little bit of weight can help people manage type 2 diabetes. The American Diabetes Association says dropping 10 to 15 pounds can help you control your diabetes.
"It's not just losing the weight, though," Eckel added. "Keeping it off is important."
The findings were published in April in Diabetologia.
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