People who maintain a healthy body weight may be less likely to develop type 2 diabetes even if they have a family history of the disease, according to new research.
Scientists have long considered type 2 diabetes a multifactorial disease, believing that genetics, environmental factors, diet, lifestyle choices, and weight all affect a person’s risk for developing the disease. But a new study published in April 2020 in Diabetologia suggests that weight alone can be an independent risk factor for type 2 diabetes.
When researchers looked at different risk factors, they found that people with obesity were more than 5 times as likely to develop type 2 diabetes compared with individuals at a healthy weight. A genetic predisposition was associated with a doubled risk of type 2 diabetes, and unfavorable lifestyle habits were tied to an 18 percent greater risk.
The study also found that people with little genetic predisposition for diabetes still had a more than eight-fold greater risk of developing the condition when they were obese.
“The associations of genetic and lifestyle risk scores with incident type 2 diabetes are relatively modest compared with the association of obesity with diabetes risk, underlining the importance of weight management in diabetes prevention,” says study coauthor Hermina Jakupović, master of science, of the University of Copenhagen in Denmark.
A study published in August 2018 in JAMA Cardiology analyzed U.K. Biobank data and found people with unhealthy behaviors had a more than tenfold greater risk of obesity, independent of their genetic predisposition for obesity.
Yet this prior study used a composite “unfavorable lifestyle” score that considered obesity as a risk factor equal to smoking, inactivity, and unhealthy eating habits. It didn’t show whether obesity might play a bigger or smaller role in the development of diabetes than other risk factors, like a sedentary lifestyle or poor food choices.
Obesity Affects Type 2 Diabetes Risk More Than Diet and Lifestyle Habits
Researchers designed the current study to look at obesity separately from these other lifestyle factors.
They examined data on 4,729 people who developed type 2 diabetes and a randomly selected cohort of 5,402 individuals who didn’t develop the disease over a median follow-up period of 14.7 years.
At the start of the study, 33 percent of the people who went on to develop type 2 diabetes were obese, and another 46 percent were overweight. Among those who didn’t develop diabetes, 22 percent were obese and 43 percent were overweight.
People who later developed type 2 diabetes were also slightly less likely to get regular exercise, limit their alcohol intake, or have healthy eating habits. They were, however, slightly less likely to be current smokers.
Also, individuals who developed type 2 diabetes were also more likely to start out with a high genetic predisposition for the disorder: About 23 percent of them had a high genetic risk compared with 20 percent of the people who didn’t develop the disease.
Obesity Triggers Insulin Resistance and Chronic Inflammation
There are several ways that obesity contributes to the development of diabetes, says Bernard Srour, PhD, PharmD, of the French Institute of Health and Medical Research INSERM in Paris.
Obesity induces chronic inflammation as well as insulin resistance, an inability to use the hormone insulin to convert blood sugar into energy that can eventually lead to type 2 diabetes, says Dr. Srour, who wasn’t involved in the study.
Physical activity may indirectly help lower the risk of diabetes by helping people to lose weight or maintain a healthy weight, Srour adds. Exercise can also help reduce insulin resistance and improve blood sugar control.
As for diet, several foods are linked to a higher diabetes risk, especially red and processed meat, and sugary drinks, Srour says. Other foods — particularly yogurt, whole grains, and vegetables — are associated with a decreased risk.
“These factors would therefore impact diabetes risk in both people with and without genetic predisposition of diabetes,” Srour says.
One limitation of the current study is that it included mostly white Europeans of a similar genetic ancestry, making it possible that results would be different for people from other parts of the world or from other racial and ethnic groups.
Weight Loss Via Diet and Lifestyle Changes Can Help Prevent Type 2 Diabetes
“If reproducible worldwide, the main message is that type 2 diabetes may be preventable,” says Ricardo Cohen, MD, of the Center for the Treatment of Obesity and Diabetes at Hospital Oswaldo Cruz in Sao Paulo, Brazil. Dr. Cohen, who wasn’t involved in the study, says targeting obesity through diet and lifestyle counseling may be the best way for healthcare professionals to help their patients avoid type 2 diabetes.
Weight management and weight loss are already the most important treatment strategies for people who have type 2 diabetes and for individuals at high risk for developing the disease, says Anita Courcoulas, MD, MPH, chief of minimally invasive bariatric and general surgery at the University of Pittsburgh in Pennsylvania.
Lifestyle changes like exercising more and adopting a healthier diet may help people lose 4 to 10 percent of their weight, says Dr. Courcoulas, who wasn’t involved in the study. Bariatric surgery can result in 27 to 35 percent weight loss, she says.
Echoing Cohen, Courcoulas says it makes sense for diabetes prevention efforts to focus most on obesity.
“Obesity, sedentary lifestyle, and genetics are each, by themselves, known to contribute to the risk for developing type 2 diabetes,” Courcoulas says. “This study adds to our understanding by finding that obesity, by itself, is likely the largest and most powerful contributing factor to the development of type 2 diabetes and ‘overpowers’ both poor lifestyle and genetic risk.”