New research released Wednesday underscores the role of obesity in type 2 diabetes. It suggests that obesity plays a major factor in up to half of new diabetes cases that occur annually in the U.S.
The link between obesity and type 2 diabetes — a condition where blood sugar levels become uncontrollable and stay too high — is well established. But the authors say their new study, published in the Journal of the American Heart Association, provides a more recent estimate on how often obesity contributes to diabetes, one that relies on longer term data than past studies have used. The study was led by researchers at Northwestern University’s Feinberg School of Medicine in Chicago.
They looked at years of data from two sources. One was the National Health and Nutrition Examination Survey (NHANES), a yearly survey that asks a nationally representative group of Americans about their lifestyle and eating habits. The other was the Multi-Ethnic Study of Atherosclerosis (MESA), an ongoing study of over 6,000 volunteers who have had their health tracked since 1999 in order to study heart disease. The combined data gave the researchers two different ways to study the health of Americans over a long period of time, particularly middle-aged to older people.
Between 2001 to 2004, according to the NHANES data, about 34% of Americans between the ages of 45 and 79 met the criteria for obesity (a body mass index, or BMI, of 35 and over); by the years 2013 to 2016, that had changed to 41%. In the MESA data, 11.6% of participants with no preexisting diabetes developed the condition over a median length of nine years. And those who were obese in the MESA study were about three times as likely as non-obese people to eventually develop diabetes during that period (20% versus 7.3%).
Based on both the MESA and NHANES data, the researchers estimate that obesity is now associated with 30% to 53% of new diabetes cases seen annually. The impact of this relationship isn’t equal across all groups of people, though. Both obesity and type 2 diabetes are more common among people of colour than whites, and Black and Hispanic Americans are also more likely to die from diabetes. But the connection between obesity and diabetes was actually strongest in white women, despite this group having the lowest obesity rates overall.
“Our study highlights the meaningful impact that reducing obesity could have on type 2 diabetes prevention in the United States. Decreasing obesity needs to be a priority,” said lead study author Natalie Cameron, a resident internal medicine physician at Northwestern University in Chicago, in a statement released by the American Health Association, which helped fund this study along with the federal government. “Public health efforts that support healthy lifestyles, such as increasing access to nutritious foods, promoting physical activity and developing community programs to prevent obesity, could substantially reduce new cases of type 2 diabetes.”
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Other research has found that the incidence of new diabetes cases in the U.S. declined between 2008 and 2018, even as the obesity rate has climbed over that same time. But the rate of new annual cases hasn’t dropped in people younger than 20, and diabetes is still the seventh leading cause of death in the U.S., having contributed to 87,647 deaths in 2017. The authors are also worried that the covid-19 pandemic could further worsen the situation, both directly and indirectly (some research has even suggested that covid-19 infection can directly contribute to new-onset diabetes).
“The greater severity of covid-19 infection in individuals with obesity is concerning because of the growing burden of adverse health consequences they could experience in the coming years; therefore, further efforts are needed to help more adults adopt healthier lifestyles and hopefully reduce the prevalence of obesity,” said senior study author Sadiya Khan in a statement.